MESSENGER

 

MDIS CDR/RDR SOFTWARE INTERFACE SPECIFICATION

 

Version 1.2.21

 

 

 

 

 

 

Prepared by:

 

Scott Murchie, Alan Mick, Louise Prockter, and Andrew Rivkin

JHU/APL

 

Edward Guinness and Jennifer Ward

PDS Geosciences Node

Washington University

 

 

Updated March 30, 2016


DOCUMENT REVIEW

This document and the archive it describes have been through PDS Peer Review and have been accepted into the PDS archive.

Scott Murchie, MESSENGER Co-Investigator/MDIS, has reviewed and approved this document.

Patricia Garcia, PDS Imaging Node Representative, has reviewed and approved this document.

Susan Ensor, MESSENGER Science Operations Center Lead, has reviewed and approved this document.


DOCUMENT CHANGE LOG

Date

Description

Sections affected

UNK

Initial Draft

All

2/11/08

Reformatted and updated, JW & SM

All

4/29/08

Updated description of data quality index

Updated description of pivot-related keywords

Updated description of shifting of image due to pixel binning

All

11/19/08

Updated description of pivot-related keywords

Updated description of CDR and DDR labels and keywords

Updated CDR and DDR index tables

Update filter bandpass descriptions

All

2/13/09

Updated keywords in Table 3-3

Table 3-3

9/3/09

Updated keywords as result of flight software update.

Added description of geographic distribution of BDRs

Added description of directory structure for BDRs

Redefined file names for BDRs and MDRs to add tile numbers

Added description of stacking order of component images BDRs and MDRs

Updated index table

Sections 2.5 and 3, Appendices B, C, D.

9/3/09

Added OBSERVATION_TYPE, SITE_ID, ORBIT_NUMBER to labels.

Updated descriptions of data quality index fields.

Section 3.3.5, Appendices B, C, D.

6/10/11

Replaced document approvals with document review information.

Updated descriptions of number of bits per pixel in EDRs and of values of

WVLRATIO.

Made additional minor edits.

Document Review

Appendix B

8/1/11

Updated for PDS peer review comments.

Updated link to NASAView.

Changed formatting of OBSERVATION_TYPE

Section 4.2, Appendix B

5/1/12

Revised BDR and MDR data product descriptions and labels.

Updated CDR sample label.

Sections 2.4.3, 2.4.4, 2.5.2.3, 3.3.7, 3.3.8, Appendices C, E, F

5/15/12

Added VOLUME_ID information.

Section 3.3

5/16/12

Updated document name for Applicable Document 4. 

Reference Applicable Document 4 for PDS delivery schedule and mission phase definitions. 

Remove out-of-date mission phase definitions in Appendix K.

Sections 1.3, 2.5.4

Appendices B, K

5/22/12

Updated description of BDR and MDR tiles, and map projection keywords.

Updated BDR and MDR index table columns.

Sections 2.4.3, 2.4.4, 3.3.7, 3.3.8, Table 3.4

8/30/12

Updated description of BDR and MDR tiles.

Updated descriptions of browse products.

Updated descriptions of OBSERVATION_TYPE

Sections 2.4.3, 2.4.4, 3.3.7, 3.3.8, 3.3.11, Appendix B

9/28/12

Clarified boundaries of MDR and BDR tiles.

Descriptions of imaging campaigns and relationships to BDRs and MDRs updated.

Sections 2.2, 2.3, 2.4

11/26/12

Descriptions of image stacking orders in BDRs and MDRs updated.

Extended mission observation type descriptions updated

Contents of CALIB directory updated

Description of calibration procedure updated

Updated descriptions of MDR and BDR tiles

Sections 2, 3

5/31/13

Extended mission 2 observation type descriptions updated

Description of 3-color map RDRs (MD3s) added

Typos fixed

Sections 2, 3, Appendix G

6/12/13

Updated file naming convention to reference “36.3” rule versus “27.3” rule.

Section 3.3

6/12/14

Description of 5-color map RDRs (MP5s) added

Description of high-incidence angle map illuminated from the east RDRs (HIEs) added

Description of high-incidence angle map illuminated from the west RDRs (HIWs) added

Description of low-incidence angle map RDRs (LOIs) added

Description of regional targeted mosaics (RTMs) added

All

6/12/14

Changed “Experimental Data Record” to “Experiment Data Record”. Made updates to CDR/DDR file naming conventions that were implemented due to spacecraft clock reset. Updated MET descriptions in the MDIS instrument raw parameters.

1.3, 3.3.5.1, 3.3.6.1, Appendix B

8/7/14

Added MDR to the list of volumes that contain a CALIB directory.

3.3

9/11/14

Fixed inconsistencies in instrument description

Corrected errors in equations for map projection

Clarified various terms

Updated descriptions of most map products

All

9/18/14

Reconciled various versions of document

Additional edits based on peer review comments

All

9/29/14

Added MECURY ORBIT YEAR 4 and MERCURY ORBIT YEAR 5 to list of mission phases

Replaced HIE, HIW, LOI, MP5, and RTM labels

Appendices B, H-L

9/30/14

Fixed minor typos.

All

2/1/16

Added descriptions of End-of-Mission data products including revisions to file structures, calibrations, and photometric corrections

All

3/30/16

Final updates for End-of-Mission.

All


CONTENTS

1. INTRODUCTION................................................................................................................... 10

1.1 Purpose and Scope................................................................................................................................................................ 10

1.2 Contents................................................................................................................................................................................... 11

1.3 Applicable Documents and Constraints........................................................................................................................... 11

1.4 Relationships with Other Interfaces................................................................................................................................. 12

2. Data Product Characteristics and Environment................................ 12

2.1 Instrument Overview........................................................................................................................................................... 12

2.1.1 Hardware Overview....................................................................................................................................................... 13

2.1.2 Pivot Mechanism........................................................................................................................................................... 14

2.1.3 MDIS Data Compression............................................................................................................................................. 16

2.1.4 Exposure Control........................................................................................................................................................... 18

2.1.5 Optical Design................................................................................................................................................................. 19

2.1.6 Filters................................................................................................................................................................................ 21

2.1.7 Flatfield Non-uniformity.............................................................................................................................................. 22

2.1.8 Dark Columns................................................................................................................................................................ 22

2.1.9 Pixel Shift Due to Pixel Binning................................................................................................................................... 23

2.2 Flyby Imaging Overview.................................................................................................................................................... 23

2.3 Orbital Imaging Overview................................................................................................................................................. 24

2.3.1 Primary Mission (Solar days 1-2)................................................................................................................................ 24

2.3.2 Extended Mission 1 (Solar days 3-4)......................................................................................................................... 26

2.3.3 Extended Mission 2 (Solar day 5 through end of mission in solar day 9)........................................................... 27

2.4 Data Product Overview....................................................................................................................................................... 29

2.4.1 CDRs................................................................................................................................................................................ 29

2.4.2 DDRs................................................................................................................................................................................ 29

2.4.3 BDRs................................................................................................................................................................................ 29

2.4.4 MDRs............................................................................................................................................................................... 30

2.4.5 MD3s................................................................................................................................................................................ 30

2.4.6 MP5s................................................................................................................................................................................ 31

2.4.7 HIEs................................................................................................................................................................................. 31

2.4.8 HIWs................................................................................................................................................................................ 32

2.4.9 LOIs.................................................................................................................................................................................. 32

2.4.10 RTMs............................................................................................................................................................................. 33

2.5 Data Processing..................................................................................................................................................................... 34

2.5.1 Data Processing Level................................................................................................................................................... 34

2.5.2 Data Product Generation.............................................................................................................................................. 35

2.5.3 Data Flow and Transmittal to PDS............................................................................................................................. 39

2.5.4 Transmittal Time Line.................................................................................................................................................. 40

2.6 Standards Used in Generating Data Products................................................................................................................ 40

2.6.1 PDS Standards................................................................................................................................................................ 40

2.6.2 Time Standards.............................................................................................................................................................. 40

2.6.3 Coordinate Systems...................................................................................................................................................... 41

2.6.4 Data Storage Conventions........................................................................................................................................... 41

2.7 Data Validation..................................................................................................................................................................... 41

3. DETAILED DATA PRODUCT SPECIFICATIONS......................................................... 43

3.1 Data Product Structure and Organization..................................................................................................................... 43

3.2 Geometric Elements............................................................................................................................................................. 43

3.3 Archive Volume Structure and Contents......................................................................................................................... 43

3.3.1 Root Directory................................................................................................................................................................ 44

3.3.2 Index Directory.............................................................................................................................................................. 44

3.3.3 Catalog Directory........................................................................................................................................................... 47

3.3.4 Document Directory...................................................................................................................................................... 48

3.3.5 CDR Directory (CDR Volumes Only)......................................................................................................................... 48

3.3.6 DDR Directory (DDR Volumes Only)......................................................................................................................... 52

3.3.7 BDR Directory (BDR Volumes Only)......................................................................................................................... 55

3.3.8 MDR Directory (MDR Volumes Only)....................................................................................................................... 59

3.3.9 MD3 Directory (MD3 Volumes Only)........................................................................................................................ 63

3.3.10 MP5 Directory (MP5 Volumes Only)....................................................................................................................... 67

3.3.11 HIE Directory (HIE Volumes Only)......................................................................................................................... 70

3.3.12 HIW Directory (HIW Volumes Only)...................................................................................................................... 74

3.3.13 LOI Directory (LOI Volumes Only).......................................................................................................................... 78

3.3.14 RTM Directory (RTM Volumes Only)..................................................................................................................... 81

3.3.15 Calib Directory............................................................................................................................................................. 84

3.3.16 Geometry Directory..................................................................................................................................................... 87

3.3.17 Browse Directory......................................................................................................................................................... 87

3.3.18 Extras Directory........................................................................................................................................................... 88

4. Applicable Software................................................................................................ 90

4.1 Utility Programs................................................................................................................................................................... 90

4.2 Applicable PDS Software Tools........................................................................................................................................ 90

4.3 Tutorial information........................................................................................................................................................... 90

Appendix A. Data Archive Terms.............................................................................. 91

APPENDIX B. LABEL AND HEADER DESCRIPTIONS.................................................. 92

APPENDIX c. CDR Label.................................................................................................. 121

APPENDIX d. DDR Label.................................................................................................. 125

APPENDIX e. BDR Label.................................................................................................. 129

APPENDIX f. MDR Label.................................................................................................. 131

APPENDIX G. MD3 Label.................................................................................................. 133

APPENDIX h. MP5 Label................................................................................................... 135

APPENDIX i. HIE Label...................................................................................................... 137

APPENDIX j. HIW Label.................................................................................................... 139

APPENDIX K. LOI Label.................................................................................................... 141

APPENDIX L. RTM Label.................................................................................................. 143

APPENDIX M. atmel th7888a Data sheet............................................................. 145


 

FIGURES AND TABLES

 

Figure 1-1: MDIS Instrument (exterior view).......................................................................... 10

Table 2-1:  MDIS Camera Details............................................................................................ 13

Figure 2-2:  MESSENGER Spacecraft Instrument Deck.................................................... 13

Figure 2-3:  MDIS Design......................................................................................................... 15

Figure 2-4:  Range of motion of the MDIS pivot platform.................................................... 16

Figure 2-5a:  MDIS/DPU Real-time Compression flowchart.............................................. 17

Figure 2-5b:  MESSENGER Main Processor (MP) image post-processing flowchart... 17

Figure 2-6:  Mapping of 12 bits to 8 bits using onboard look-up tables............................ 18

Figure 2-7:  Autoexposure algorithm decision tree.............................................................. 19

Figure 2-8:  WAC optical layout............................................................................................... 20

Table 2-9:  MDIS specifications............................................................................................... 20

Figure 2-10:  NAC optical layout............................................................................................. 21

Table 2-11:  WAC Filters Specifications................................................................................ 21

Figure 2-12:  Non-uniformity due to dust particles............................................................... 22

Figure 2-13:  Pixels intended for dark columns, and actual pixels in binned images... 23

Table 2-14:  Definitions of MDIS data products.................................................................... 34

Table 2-15:  Processing Levels for Science Data Sets....................................................... 34

Table 2-16:  Solar irradiance used to convert radiance to units of I/F.............................. 37

Figure 2-17:  Sequential processing of EDRs to yield RDRs............................................ 39

Table 3-1:  Root Directory Contents........................................................................................ 44

Table 3-2:  Index Directory Contents...................................................................................... 45

Table 3-3:  CDR/DDR Index Table Contents........................................................................ 46

Table 3-4:  BDR/MDR/MD3/MP5/HIE/HIW/LOI/RTM Index Table Contents.................... 47

Table 3-5:  Catalog Directory Contents.................................................................................. 47

Table 3-6:  Document Directory Contents............................................................................. 48

Table 3-7:  Filter numbers and their bandpasses................................................................. 49

Table 3-8.  MDIS-specific values for CDR label keywords................................................. 52

Table 3-9.  MDIS-specific values for DDR label keywords................................................. 55

Table 3-10. Latitude and longitude limits of Mercury Charts.............................................. 56

Table 3-11.  MDIS-specific values for BDR label keywords............................................... 59

Table 3-12.  MDIS-specific values for MDR label keywords............................................... 63

Table 3-13.  MDIS-specific values for MD3 label keywords............................................... 67

Table 3-14.  MDIS-specific values for MP5 label keywords................................................ 70

Table 3-15.  MDIS-specific values for HIE label keywords................................................. 74

Table 3-16.  MDIS-specific values for HIW label keywords................................................ 77

Table 3-17.  MDIS-specific values for LOI label keywords.................................................. 81

Table 3-18.  MDIS-specific values for RTM label keywords............................................... 84

Table 3-19:  Calib Directory Contents.................................................................................... 87

 

 

 


ACRONYMS AND ABBREVIATIONS

ACT

Applied Coherent Technology Corporation

APL

The Johns Hopkins University Applied Physics Laboratory

ASCII

American Standard Code for Information Interchange

BDR

Map Projected Basemap Reduced Data Record

BP

Bandpass

BW

Bandwidth

CCD

Charge-Coupled Device

CDR

Calibrated Data Record

CODMAC

Committee on Data Management and Computation

DDR

Derived Data Record

DN

Data Number

DPU

Data Processing Unit

DVD

Digital Video Disc

e

Emergence angle of reflected light, relative to local surface normal

EDR

Experiment Data Record

FOV

Field-of-view

FPGA

Field-programmable Gate Arrays

FTP

File Transfer Protocol

FWHM

Full Width at Half Maximum

g

Phase angle of reflected sunlight measured at MDIS

HIE

Map Projected High-incidence Angle Basemap Illuminated from the East RDR

HIW

Map Projected High-incidence Angle Basemap Illuminated from the West RDR

IAU

International Astronomical Union

i

Incidence angle of solar illumination, relative to local surface normal

I/F

Intensity divided by flux, or the ratio of radiance to incident solar irradiance

IFOV

Instantaneous field-of-view

ISO

International Standards Organization

JHU/APL

The Johns Hopkins University Applied Physics Laboratory

JPL

Jet Propulsion Laboratory

LOI

Map Projected Low-incidence Angle Basemap Reduced Data Record

MASCS

MESSENGER Mercury Atmospheric and Surface Composition Spectrometer

MESSENGER

MErcury, Surface, Space ENvironment, GEochemistry, and Ranging

MDIS

MESSENGER Mercury Dual Imaging System

MD3

Map Projected Multispectral Reduced Data Record  (3-Color)

MDR

Map Projected Multispectral Reduced Data Record (8-Color)

MET

Mission Elapsed Time

MLA

MESSENGER Mercury Laser Altimeter

MOC

Mission Operations Center

MP

Main Processor

MP5

Map Projected Multispectral Reduced Data Record (5-Color)

NAC

Narrow Angle Camera

NAIF

Navigation and Ancillary Information Facility

NASA

National Aeronautics and Space Administration

OCF

Optical Calibration Facility

PCK

Planetary Constant Kernel (SPICE)

PDS

Planetary Data System

PNG

Portable Network Graphics (file format)

RDR

Reduced Data Record

RTM

Map Projected Regional Targeted Mosaic Reduced Data Record

SIS

Software Interface Specification

SOC

Science Operations Center

SNR

Signal-to-noise Ratio

SQL

Structured Query Language

SPICE

Spacecraft Planet Instrument C-matrix Events; a set of data formats for spacecraft ephemeris, attitude, and instrument pointing

SSR

Solid State Recorder

TBD

To Be Determined

UTC

Coordinated Universal Time

WAC

Wide Angle Camera

 

 



 

1. INTRODUCTION

1.1 Purpose and Scope

This Software Interface Specification (SIS) describes the organization and contents of the MESSENGER Mercury Dual Imaging System (MDIS) Calibrated Data Record (CDR) and Reduced Data Record (RDR) archive.  This archive includes data from the two cameras onboard the MESSENGER spacecraft: the Wide Angle Camera (WAC) and the Narrow Angle Camera (NAC) (see Figure 1-1 below).  The MDIS CDR/RDR data products are deliverable to the Planetary Data System (PDS) and the scientific community that it supports.  All data formats are based on the PDS standard.

 

 

Figure 1-1: MDIS Instrument (exterior view).

 

 

There are ten MDIS data sets defined in this SIS document.  These include:

 

1) Calibrated Data Records (CDRs)

2) Derived Data Records (DDRs)

3) Map Projected Basemap Reduced Data Records (BDRs) containing a global 750-nm mosaic illuminated for morphology, with a typical solar incidence angle near 68° (version 0, 74° for version 1)

4) Map Projected Multispectral Reduced Data Records (MDRs) containing an 8-color global map illuminated at a minimized solar incidence angle

5) Map Projected Multispectral Reduced Data Records (MD3s) containing a 3-color regional map illuminated at a minimized solar incidence angle

6) Map Projected Multispectral Reduced Data Records (MP5s) containing a 5-color regional map of the northern hemisphere illuminated at a minimized solar phase angle

7) Map Projected Basemap Reduced Data Records containing a global 750-nm mosaic illuminated at high solar incidence angle from the east, to accentuate low relief morphology (HIEs)

8) Map Projected Basemap Reduced Data Records containing a global 750-nm mosaic illuminated at high solar incidence angle from the west, to accentuate low relief morphology (HIWs)

9) Map Projected Basemap Reduced Data Records containing a global 750-nm mosaic illuminated at a minimized solar incidence angle, to accentuate albedo variations (LOIs)

10) Map Projected Regional Targeted-observation Mosaics containing one or more NAC or WAC frames pointed at a high science priority region of interest (RTMs)

These data sets are defined in section 2.4 and described in more detail in sections 3.3.5 through 3.3.14 of this document.

This SIS is useful to those who wish to understand the format and content of the MDIS data products and ancillary support data.  The SIS applies to the MDIS CDR/RDR data products produced during the course of MESSENGER preflight calibration and mission operations.  The users for whom this SIS is intended are the scientists who will analyze the data, including those associated with the MESSENGER Project and those in the general planetary science community.

1.2 Contents

This Data Product SIS describes how data products generated by the MESSENGER team are processed, formatted, labeled, and uniquely identified.  The document details standards used in generating the products and software that may be used to access the products.  Data product structure and organization is described in sufficient detail to enable a user to read the product.  Finally, an example of each product label is provided.

1.3 Applicable Documents and Constraints

This MDIS CDR/RDR SIS is responsive to the following documents:

  1. MESSENGER Mercury: Surface, Space Environment, Geochemistry, Ranging: A mission to Orbit and Explore the Planet Mercury, Concept Study, March 1999.
  2. Planetary Data System Archive Preparation Guide (APG), August 29, 2006, Version 1.1, JPL D-31224.
  3. Planetary Data System Standards Reference, February 27, 2009, Version 3.8, JPL D-7669, Part-2.
  4. MESSENGER Data Management and Archiving Plan, The Johns Hopkins University APL, 7384-9019.
  5. [PLR] Appendix 7 to the discovery program Plan: Program Level Requirement for the MESSENGER Discovery project, June 20, 2001.
  6. MESSENGER Instrument DPU/MDIS Flight Software Specification, John Hayes, 7390-9041, Revision a, Feb. 26, 2004.  Describes the instrument flight software.
  7. MDIS Compression Description, Pat Murphy, Internal APL Memo SRM-03-056, Aug. 25, 2003.  Describes the MESSENGER Main Processor wavelet compression, sub-framing and binning flight software.
  8. Hawkins, S. E., III, et al., Multi-Spectral Imager on the Near Earth Asteroid Rendezvous mission, Space Sci. Rev., 82, 31-100, 1997.
  9. Hawkins, S.E., III, et al., The Mercury Dual Imaging System on the MESSENGER Spacecraft, Space Sci Rev 131: 247–338, DOI 10.1007/s11214-007-9266-3, 2007.
  10. Hansen, O. L., Surface temperature and emissivity of Mercury, Astrophys. J., 190, 715-717, 1974.
  11. MESSENGER Mercury Dual Imaging System (MDIS) Experiment Data Record (EDR) Software Interface Specification (SIS) document, The Johns Hopkins University, APL, V2T, Jun. 28, 2015.
  12. Archinal, B.A. et al., Report of the IAU Working Group on Cartographic Coordinates and Rotational Elements: 2009, 2010.
  13. Domingue, D.L., Denevi, B.W., Murchie, S.L., and Hash, C.D., Application of multiple photometric models to disk-resolved measurements of Mercury’s surface: Insights into Mercury’s regolith characteristics, Icarus, 268, 172-203, 2016.
  14. Denevi, B.W. et al., Final calibration and multispectral map products from the Mercury Dual Imaging System Wide-Angle Camera on MESSENGER, Lunar Planet. Sci 47, abstract #1264.
  15. Becker, K.J. et al., First global digital elevation model of Mercury, Lunar Planet. Sci 47, abstract #2959.

1.4 Relationships with Other Interfaces

Data products described in this SIS are produced by the MESSENGER Science Operations Center (SOC).  Changes to the SOC processing algorithms may cause changes to the data products and, thus, this SIS.  The MDIS CDR/RDR products are derived from MDIS Experiment Data Record (EDR) products.  As such, changes to the EDR product may affect the CDR/RDR products.  Changes in MDIS data products or this SIS may affect the design of the MDIS archive volumes.

2. Data Product Characteristics and Environment

2.1 Instrument Overview

The Wide Angle Camera (WAC) has 12 band pass filters, while the Narrow Angle Camera (NAC) is monochromatic (has a single filter).  Table 2-1 summarizes relevant parameters for both the WAC and NAC cameras.  The CDR format for each camera is identical.

 

 

Narrow Angle Camera (NAC)

Wide Angle Camera (WAC)

Field of View

1.5 degree

10.5 degree

Scan Range

-40ľ to +50ľ from spacecraft +z

-40ľ to +50ľ from spacecraft +z

Exposure Time

1 to 9989 ms

1 to 9989 ms

Frame Transfer Time

3.4 ms

3.4 ms

Image Readout Time

1 s

1 s

Spectral Filters

1

12 positions

Focal Length

550 mm

78 mm

Collecting Area

462 mm2

48 mm2

Detector- TH7888A

CCD 1024 x 1024, 14 Ķm pixels

CCD 1024 x 1024, 14 Ķm pixels

Pixel FOV

5.1 m at 200 km altitude

35.8 m at 200 km altitude

Table 2-1:  MDIS Camera Details.

 

2.1.1 Hardware Overview

Most of the MESSENGER instruments are fixed-mounted (Figure 2-2), so that coverage of Mercury is obtained by spacecraft motion over the planet.  The imaging system uses a pivot platform to accommodate flyby imaging and optical navigation, as well as imaging during the orbital phase.

 

Description: Description: Description: Description: C with instrument location

Figure 2-2:  MESSENGER Spacecraft Instrument Deck.

 

The full MDIS instrument includes the pivoting dual camera system as well as the two redundant external Data Processing Units (DPUs).  The dual camera assembly without the DPUs is usually simply referred to as “MDIS.”  The overall design and look of MDIS, shown in Figure 2-3, was driven by mass limitations, the severe thermal environment at Mercury, and the requirement for a large field-of-regard for optical navigation and off-nadir pointing.  The total mass of MDIS is 8.32 kg, including flight blankets, harness to DPU, and thermal gasket.

The pivot platform houses the multispectral WAC and the monochrome NAC.  The thermal design generally maintained the CCD detectors in the WAC and NAC within their desired operating temperature range of -45°C to -10°C; during the hottest parts of Mercury orbit, occasional excursions above this range occurred.  Only one DPU may be active at a time, and due to thermal constraints only one camera will operate at a time; however, observations with the two cameras can be interleaved at 5-s intervals.  A separate electronics assembly accommodates switching between the various modes of operating with the redundant DPUs.  The pivot platform has a large range of motion (~240°) to allow the cameras to be “tucked away” to protect the optics from contamination.

2.1.2 Pivot Mechanism

The MDIS pivot platform is controlled by a stepping motor (Fig. 2-3). The motor phases are controlled directly by the DPU software to move the platform. The phase pattern can be adjusted by software to move the platform forwards or backwards.  The pivot platform’s range of motion is mechanically constrained by “hard” stops.  The range of motion is further constrained by “soft” stops applied by the software.  The nominal allowed range is shown in Fig. 2-4.  The total range of motion of MDIS is about 240°, limited by hard mechanical stops in the pivot motor.   The hard stops are fixed at -185ľ and 55ľ.  The pivot motor drive-train provides precision rotation over the 90° operational range of motion (Figure 2-4) about the spacecraft +Z axis.

The MDIS pivot actuator is capable of accurately stepping in intervals of 0.01° (~150 Ķrad) per step.  Crude pointing knowledge is determined by first “homing” the instrument, which is accomplished by driving the actuator into one of the mechanical hard stops for a period of time sufficient to ensure the orientation of the instrument if it had been previously stopped at the opposite extreme of travel.  The rotational speed of the pivot platform is 1.1°/s.  Once the location of the pivot actuator is known, the flight software retains this knowledge and subsequent pointing commands are achieved by counting pulses (steps) to the motor.

There are two alternative measures of pivot position: by counting motor steps following homing, as described above, or by using the position returned from a pivot position resolver. The latter method, augmented by inflight calibration of resolver readings using stellar pointing calibrations, is used for the most accurate determination of pivot pointing for construction of SPICE camera kernels and for production of map products.

Figure 2-3:  MDIS Design.

 

Description: Description: Description: Description: Fig_2-4

 

Figure 2-4:  Range of motion of the MDIS pivot platform. Operational range is -40° sunward to +50° antisunward (planetward). When stowed, the sensitive first optic of each telescope is protected.

 

2.1.3 MDIS Data Compression

The MESSENGER mission requires compression to meet its science objectives within the available downlink. Figure 2-5 summarizes the compression options available to MDIS at the instrument level and using the spacecraft main processor (MP). At the focal plane, 2×2 binning is available on-chip to reduce the 1024×1024 images to 512×512 format, 12-bit data number (DN) levels can be converted to 8 bits, and data can be compressed losslessly. After data are written to the recorder, they can be uncompressed and recompressed by the MP more aggressively using any of several options: additional pixel-binning, subframing, and lossy compression using an integer wavelet transform. The strategy for MP compression is that most data except flyby imaging are wavelet compressed, typically 4:1 for monochrome data and to a lower ratio (≤ 4:1) for orbital color data. Color imaging but not monochrome imaging may be further pixel-binned. For the special case of optical navigation images, there is a “jailbar” option that saves selected lines of an image at a fixed interval for optical navigation images of Mercury during flyby approaches.

 

Description: Description: Description: Description: image_compression

Figure 2-5a:  MDIS/DPU Real-time Compression flowchart.

 

 

 

Description: Description: Description: Description: Fig_2-5b

Figure 2-5b:  MESSENGER Main Processor (MP) image post-processing compression flowchart.

 

Description: Description: Description: Description: fig_04

Figure 2-6:  Mapping of 12 bits to 8 bits will be accomplished using onboard look-up tables.  The tables are designed to preferentially preserve information at different DN ranges, and they can accommodate a nominal detector dark level as well as one that has changed with time.  “Noise” refers to the read noise, which is “low” (1 12-bit DN) for the WAC CCD and “high” (2 12-bit DNs) for the NAC CCD.  (1) Low noise, high bias SNR proportional.  Usage: Typical imaging with varied brightness. Nominal for most imaging.  (2) Low noise, high bias DN-weighted SNR proportional.  Usage: Faint object imaging.  (3) High noise, high bias DN-weighted SNR proportional.  Usage: B/W, low brightnesses.  Nominal for NAC imaging.  (4) Low noise, medium bias SNR proportional.  (5) Low noise, medium bias DN-weighted SNR proportional.  Usage: Faint objects.  (6) High noise, medium bias DN-weighted SNR proportional.  Usage: B/W mostly low brightness.  (7) Zero-bias SNR proportional.  Usage: Typical imaging, varied brightness.  (8) Linear.  Usage: High brightness mapping, preserves high DN information.

2.1.4 Exposure Control

The exposure time of images can be set manually by command or automatically by the software.  In manual mode, a full 9989 ms range of exposure times is available.  In automatic mode, the exposure time of the next image is computed by the DPU software (Fig. 2-7).  This computation has two distinct steps.  The first step computes a new exposure time based on the brightness of a test image.  The second step anticipates commanded filter wheel motion to a new filter and adjusts the computed exposure time accordingly.

During the read stage of the image pipeline, the hardware generates a histogram of the image.  The histogram is analyzed by the software to determine if the image is overexposed or underexposed.  First, the histogram is scaled by a factor of four if it comes from a 2×2 binned image.  If the brightest histogram value (except for a commandable number of allowable saturated pixels) exceeds a saturation threshold, the image is considered overexposed and the exposure time is scaled back.  Otherwise the image is considered underexposed.  Histogram values are accumulated starting from the brightest bin down towards the dimmest bin, until the saturation threshold is exceeded.  The brightness value that causes the sum to exceed the threshold is the actual image brightness.  The exposure time is scaled by the ratio of the commanded target brightness to the actual brightness, after a background brightness is removed.  The algorithm is characterized by uploadable parameters for the saturation threshold, allowable number of saturated pixels, overexposure fallback, and background brightness.

The algorithm described so far compensates for changes in scene brightness and filter wheel changes.  The next step adjusts the exposure time further if the imager, binning mode, or filter selected for the next exposure does not match what was used in the test exposure.  The exposure time is scaled by the ratio of the transmissivity (actually, the expected brightness in DN/s) of the old setup to the transmissivity of the new setup.  An uploadable table of transmissivities for the WAC filters and for the NAC imager in either binning mode are used.  Finally, the computed exposure time is forced to fall within an uploadable range but is always less than 1 second.

 

Description: Description: Description: Description: Fig_2-7

 

Figure 2-7:  Autoexposure algorithm decision tree.  A 64-bin histogram is computed in hardware for each image.  If an image is determined to be underexposed, the actual exposure is computed as Actual = minimum brightness such that the sum of the pixels above this brightness < saturation threshold.

 

2.1.5 Optical Design

The WAC (Figure 2-8) consists of a 4-element refractive telescope having a focal length of 78 mm and a collecting area of 48 mm2 (Table 2-9).  The detector located at the focal plane is an Atmel (Thomson) TH7888A frame-transfer CCD with a 1024×1024 format and 14-Ķm pitch detector elements that provide a 179-Ķrad pixel (instantaneous) field-of-view (IFOV).  See Appendix M for the Atmel TH7888A data sheet.  A 12-position filter wheel provides color imaging over the spectral range of the CCD detector.  Eleven spectral filters spanning the range from 395 to 1040 nm are defined to cover wavelengths diagnostic of different potential surface materials.  The twelfth position is a broadband filter for optical navigation and low-light imaging.  The filters are arranged on the filter wheel in such a way as to provide complementary passbands (e.g., for 3-color imaging, 4-color imaging) in adjacent positions.

 

 

 

Figure 2-8:  WAC optical layout.

 

 

 

Narrow Angle

Wide Angle

Field of view

1.5° × 1.5°

10.5° × 10.5°

Pivot range

-40° to +50°

(observational)

(Sunward)         (Planetward)

Exposure time

1 to 9989 ms

Frame transfer time

3.4 ms

Image readout time

1 s

Spectral filters

1

12 positions

Spectral range

725783 nm

3951040 nm in clear filter

Focal length

550 mm

78 mm

Collecting area

462 mm²

48 mm²

NAC-WAC coalignment knowledge

<0.01 deg (<179 μrad)

Spacecraft pointing control

<0.1 deg (<1.75 mrad)

Spacecraft pointing knowledge

0.02 deg (<350 μrad)

 

Detector-TH7888A

CCD 1024×1024, 14-μm pixels

IFOV

25 μrad

179 Ķrad

Pixel FOV

5.1 m at 200-km altitude

35.8m at 200-km altitude

Quantization

12 bits per pixel

Compression

Lossless, multi-resolution lossy, 12-to-8 bits

Transfer to DPU; transfer from DPU to SSR limited to 3 Mbps (4 s to transfer 1024×1024 image).

Table 2-9:  MDIS specifications.

 

The NAC (Figure 2-10) is an off-axis reflective telescope with an effective 550-mm focal length and a collecting area of 462 mm2.  The NAC focal plane is identical to the WAC’s, providing a 25-Ķrad IFOV.  The NAC has a single medium-band filter (50 nm wide), centered at 750 nm to match to the corresponding WAC filter for monochrome imaging.

 

Description: Description: Description: Description: mdis_nac_optics

Figure 2-10:  NAC optical layout.

 

2.1.6 Filters

The WAC camera utilizes a twelve position filter wheel with bandpasses from 430 to 1020 nm, including a broadband navigation filter centered at 750 nm.  The NAC is a broadband BW imager with a center wavelength of 747 nm and a bandpass of 53 nm.  Other than the image dimensions, the data products of each camera are identically formatted.  Table 2-9 shows the design-level focal length, collecting area, and field of view for each camera.  Table 2-11 shows the calibrated filter wheel position and bandwidth parameters, and the design-level focal lengths for each filter. More accurate values for focal lengths are derived from flight measurements, and are updated over the course of the mission as knowledge of the values improves.

Filter

Number

Filter

Filename

letter

Wavelength

(Flight)

(nm)

FWHM

(Flight)

(nm)

Total

Thickness

(mm)

Focal

length

(mm)

Scale

change

(%)

1

A

698.8

5.3

6.00

78.218

-0.104

2

B

700

600.0

6.00

78.163

-0.104

3

C

479.9

10.1

6.30

77.987

-0.329

4

D

558.9

5.8

6.30

78.023

-0.283

5

E

628.8

5.5

6.20

78.109

-0.173

6

F

433.2

18.1

6.00

78.075

-0.216

7

G

748.7

5.1

5.90

78.218

-0.033

8

H

947.0

6.2

5.20

78.449

0.262

9

I

996.2

14.3

5.00

78.510

0.340

10

J

898.8

5.1

5.35

78.390

0.186

11

K

1012.6

33.3

4.93

78.535

0.372

12

L

828.4

5.2

5.60

78.308

0.082

Table 2-11:  WAC Filters Specifications – Wavelength and FWHM Measured at -26° C.

 

For WAC spectral filters, bandpass widths were selected to provide required SNR in exposure times sufficiently short to prevent linear smear by along-track motion, yet sufficiently long (>7 ms) to avoid excessive artifacts from removal of frame transfer smear during ground processing.  SNR is not an issue, as sufficient light is available for SNRs >200, but saturation is a concern at low phase angles.  At the same time, both cameras must be sufficiently sensitive to provide star images for optical navigation.  When imaging Mercury against a star background, at least three stars must be visible per image at ≥ 7× noise with the clear filter.

2.1.7 Flatfield Non-uniformity

Response uniformity, or flat field, is a measure of pixel-to-pixel variations in responsivity.  One significant non-uniformity in the data noted during ground calibration is that of dark spots scattered across the FOV of both imagers.  The darker spots scattered across WAC images are fixed with respect to the CCD regardless of filter wheel setting, though their intensities do vary slightly with filter.  The sizes of the spots are consistent with shadows of <<35-Ķm dust on the CCD window, and their number density is consistent with the standards for a class-10,000 clean room in which the camera was assembled.  Also consistent with this hypothesis, following instrument vibration during environmental testing, the locations of several spots changed.  With the exception of a single particle (arrow, Figure 2-12) the dust spots do not significantly affect the DN levels.  The spots themselves also moved as the instrument was subjected to the vibrations of launch and flight. The original determination of the flat field was made using images of the interior of an integrating sphere, acquired during ground calibration. Inflight, several iterative improvements of the flat-field correction were performed. Images of an onboard calibration target inside the spacecraft adaptor ring, as well as of the Venus cloud tops acquired during the second Venus flyby, have been used prior to Mercury orbit insertion. After Mercury orbit insertion, medians of thousands of low-contrast field-filling images acquired through each filter provided an improved flat field.

 

Description: Description: Description: Description: Blackspot

 

Figure 2-12:  Non-uniformity due to dust particles is visible in integrating sphere images acquired through the quartz window in the OCF chamber door of the calibration facility.

2.1.8 Dark Columns

Dark models for MDIS images can be created using either (a) dark images (usually acquired with MDIS stowed against the spacecraft deck) or (b) columns lying outside of the CCD’s active area.  In the full-frame mode for either the WAC or NAC, the first four columns of each image are taken from a region of the CCD that is never exposed to light and, thus, represents a dark level that is purely a function of bias and dark current.  The dark columns are separated from the image section by five isolation columns to avoid diffusion of signal from the active area.  When the image is read out, these four columns are mapped into the first four imaging columns, so the resulting image is a square 1024 by 1024 pixels, with the first four columns replaced with the sampled dark columns.  The four dark columns behave identically to the scene as a function of row, exposure time, and temperature to within 0.26 DN.

In the binned mode for both cameras, true dark columns are unavailable due to the pixel-shift problem described in the following section.  However, the second column of a binned image provides a much lower response to light than a column in the active image area.  This lower-response column does show a temperature- and exposure-time response that can be modeled, making it a functional “dark.”  Therefore, the dark column model simply uses the second column of an image (binned or full-frame) to be a representative of the dark strip properties.

Given the problematic nature of binned “dark” columns, model (a) above is used as the basis for an analytical model of dark current.  Nevertheless, the dark strips could serve as an indicator of the variations of the CCD’s response to radiation, and, as such, a means to validate the performance of the dark model over time. 

2.1.9 Pixel Shift Due to Pixel Binning

For either camera, an error in programming the Actel field-programmable gate arrays (FPGAs) that executes binning at the focal plane results in a different sampling of the CCDs. Binned images are sampled from a part of the CCD that is offset 8 unbinned pixels (4 binned pixels) in the direction of increasing sample number in the image. This difference in pointing is accounted for in the SPICE frames kernel.

Description: Description: Description: Description: dark_columns

 

Figure 2-13:  Pixels intended for dark columns, and actual pixels used in binned images for WAC and NAC.

 

2.2 Flyby Imaging Overview

The MESSENGER trajectory provided three flyby opportunities of Mercury: January 2008, October 2008, and September 2009. During the first flyby, approximately half of the hemisphere not viewed by Mariner 10 was illuminated (subsolar longitude 190°E); the first Mercury data returned from MESSENGER thus covered new terrain, including the previously unseen western half of the Caloris Basin and its ejecta. During the second flyby, illumination was centered on the eastern edge of the Mariner 10 hemisphere (subsolar longitude 4°E). The lighting geometry for the third encounter was nearly identical to that of the second encounter with the subsolar point at the prime meridian (0°E); the approach and departure phase angles were less extreme, however, resulting in better inbound imaging. During the second and third flybys, most of the remaining unseen portion of Mercury was imaged. Total coverage between Mariner 10 and the three flybys excluded only the poles and a small longitudinal gap up to 6° wide, centered at 93°E longitude.

During each of the flybys, three major types of image mosaics were acquired. First, MDIS-NAC raster scan mosaics covered >80% of the planet at a resolution averaging ~500 m/pixel, providing a first version of a global map. Second, MDIS-WAC imaged the planet in 11 filters at as good as ~2.4 km/pixel. Finally, high-resolution WAC and NAC mosaics covered selected areas at higher resolutions.

Creating maps from imaging obtained at various photometric geometries during the flybys and from orbit requires an accurate photometric model of the planet at the wavelengths of the NAC and WAC filters. Therefore, MESSENGER began the collection of multi-geometry photometric characterization of Mercury’s surface from data acquired during the flybys, through observations of the same point on the ground acquired at the same incidence angle, but different emission and phase angles.

2.3 Orbital Imaging Overview

Imaging during the 8 solar day orbital phase is divided into two types, acquired as parts of organized mapping "campaigns", and "targeted observations" covering regions of interest specifically defined by the Science Team. In the latter case the region of interest is recorded by the SITE_ID keyword.

2.3.1 Primary Mission (Solar days 1-2)

On 18 March 2011 MESSENGER was placed in a highly elliptical orbit with a periapse of 200 km at ~64ŻN and an apoapse of 13100 km.  The orbit had an approximately 12-hour period, was inclined 80Ż to the planet’s equatorial plane, and was not sun-synchronous.  During one Mercurian solar day, the orbit precessed completely around the planet twice. At times the groundtrack was near the terminator; 22 days later it passed over the sub-solar point. The following were the major imaging campaigns during the ~1 Earth year primary mission.

2.3.1.1              Global Monochrome Basemap Campaign

One of the primary goals of MDIS is to acquire a global monochrome basemap at ~250-m/pixel average spatial sampling, low emission angle, and moderate incidence angle (45Ż-80Ż).  For a given area, coverage was first obtained when local nadir was viewed at a solar incidence angles as close as possible to 68°. This value is a compromise between higher incidence angles to highlight subtle topography and lower incidence angles to eliminate shadows. The choice of the NAC or WAC camera was driven by the necessity of maintaining both cross-track overlap and near uniform spatial resolution: the NAC was used to image the southern hemisphere, whereas the WAC was used in the northern hemisphere.  For monochrome imaging, the 750 nm filter was used in the WAC to match the 750 nm bandpass of the NAC.  This first global nadir-viewing basemap was acquired during the first Mercurian solar day of the mission (i.e., during the first half of the primary mission).

2.3.1.2              Stereo Mapping Campaign

An off-nadir stereo-complement to the above basemap consists of images taken at nearly the same local solar time one solar day later, with stereo convergence attained using off-nadir pointing up or down the groundtrack. The stereo complement was acquired on solar day two (i.e., the second half of the primary mission).

2.3.1.3              Global 8-Color Mapping Campaign

Color mapping was repeated after the flybys, improving spatial resolution by nearly a factor of 3 to 1.0 km/pixel on average.  Images were acquired using near-nadir pointing, but in contrast to the monochrome basemap, low incidence angles were targeted. The data were acquired in only 8 of the 11 filters used during the flybys, to manage data volume. In addition, 2x2 or 4x4 pixel-binning was applied at northern latitudes, also to manage data volume.

2.3.1.4              South Polar Mapping Campaign

In order to identify permanently shadowed (and permanently illuminated) areas, the south polar region was imaged repeatedly throughout each Mercurian solar day during every fourth orbit, so that all longitudes were illuminated at ~5Ż increments of solar longitude.  This strategy provides coverage of all areas near their minimum solar incidence angle, with nearly a full 180° range of solar azimuth from local sunrise to local sunset.  The campaign was divided between the two solar days.  On the first solar day, the WAC was used while the spacecraft was at high altitude at high southern latitude, providing 1.5-1.7 km/pixel image coverage extending equatorward to approximately 60Ż latitude on the dayside (70° latitude with the full azimuth range).  On the second solar day a more limited region to 75° latitude was covered at about 300 m/pixel using the NAC.

2.3.1.5              High-resolution NAC Targeted Observations

Selected areas mostly in the northern hemisphere, targeted predominantly using flyby imaging, were imaged from orbit at resolutions of typically ~20 m/pixel using strips of NAC images. Pointing was attempted to be at geometries similar to that of the global monochrome basemap. Some strips were re-imaged at an off-nadir geometry to provide stereo convergence. Additional targets were observed, usually off-nadir, at poorer resolutions and with lower incidence angles, simultaneously with measurements from the MASCS/VIRS spectrometer.

2.3.1.6              3-Color WAC Targeted Observations

Selected regions of the planet were targeted with full-resolution color imaging with spatial sampling typically ~400 m/pixel, but using only 3 color filters.  This reduced number of filters was driven by spacecraft velocity, slower cadence of the readout of unbinned images, and the need to maintain overlap between filters.  Targets were identified from Mariner 10 data and MESSENGER flyby results.

2.3.1.7              Color Photometry Targeted Observations

Orbital photometric observations complement the flyby photometry by repeatedly covering representative areas near the Rembrandt and Beethoven basins at wide variety of incidence, emission, and phase angles, initially using the same 8-color filter set as for the global 8-color map. Images of the same target are taken multiple times, as the planet's rotation varies the incidence angle as the target region moves from the terminator to near the sub-solar longitude. Later in the mission the number of filters was increased to 11 to improve photometric correction of 11-color targeted observations.

2.3.1.8              Limb Image Campaign

Once per week, three sets of 2x1 frame WAC 750-nm image mosaics are acquired at high altitudes, showing the entire limb of Mercury. These data are used to help define the low-order global shape model for Mercury.

2.3.1.9              On-orbit Calibration Campaigns

Star fields were imaged in the WAC clear filter in coordination with limb imaging, to track temporal drift in MDIS pointing due to plastic deformation of the spacecraft from thermal cycling.  In addition, periodically the MDIS pivot plane is pointed off the planet's limb and star images acquired at multiple positions within the gimbal plane that are separated by tens of degrees, and the sequence of positions is repeated over the course of an orbit. This periodic measurement is used to characterize pointing drift due to temperature dependent elastic deformation of the spacecraft structure, as well as to characterize plastic deformation.

2.3.2 Extended Mission 1 (Solar days 3-4)

In April 2012 MESSENGER executed a series of maneuvers to change the orbit and spend more time at lower altitude. The new 8-hour orbit was still highly eccentric, with MESSENGER travelling between 278 and 10,314 km above Mercury's surface. Imaging campaigns were modified to take advantage of the lower altitude and to optimize illumination and viewing compared to the "general purpose" monochrome basemap and stereo complement from the primary mission. The extended mission comprises Mercury solar days 3 and 4, through the end of March 2013.

2.3.2.10          Albedo Map and Stereo Complement Campaigns

One issue from the primary mission stereo map was its "one size fits all" illumination geometry that attempted to meet multiple objectives while being optimized for none. In order to attain stereo coverage with reduced shadows, a new pair of mosaics was acquired that used the camera selection and spatial resolution strategy from the primary mission monochrome basemap, but targeted lower solar incidence angles, 45° instead of 68°. The nadir mosaic was acquired on solar day 3, and the stereo complement on day 4. Gaps in both were filled over time.

2.3.2.11          High-incidence Mapping Campaigns (illuminated from the east and west)

To improve mapping and characterization of very low-relief features, an additional mosaic was acquired targeting a higher incidence angle than the primary mission monochrome basemap, 80° instead of 68°. Later, coverage was augmented to provide separate maps illuminated from the east and from the west.

2.3.2.12          3-Color Mapping Campaign

3-color mapping of northern and equatorial latitudes without pixel binning was conducted on solar day 3. This campaign is the equivalent of targeted color imaging from the primary mission, except with spatially continuous coverage with slowly varying illumination geometries.

2.3.2.13          North Polar Mapping Campaign

In order to identify permanently shadowed (and permanently illuminated) areas, during both solar days 3 and 4 imaging of the north polar region was conducted whenever possible to build coverage both at minimum solar incidence angle and with as large as possible a range of solar azimuths.

2.3.2.14          Ride-along Imaging Campaign

Beginning in Extended Mission 1, spare downlink was used to acquire non-targeted, high-resolution NAC images of the northern hemisphere, as "ride-along" observations during times when spacecraft pointing is optimized for other instruments.

2.3.2.15          Other Imaging

Targeted, high-resolution NAC strips, color photometry, limb images, and on-orbit calibrations continued to be acquired as during the primary mission. Regular color imaging of the southern polar region began to be used to monitor radiometric performance of the WAC.

2.3.3 Extended Mission 2 (Solar day 5 through end of mission in solar day 9)

At the end of March 2013 MESSENGER began its second extended mission, with new imaging campaigns complementing those of the Primary Mission and Extended Mission 1. The orbit around Mercury remained largely the same initially, but solar perturbations caused the periapse to approach the surface. In December 2013 the first of several low altitude (<200 km) periapse periods occurred. Each was followed by a periapse-raising maneuver. Once propellant was exhausted, the periapse intersected the surface, and active mission operations ended upon spacecraft impact on 30 April 2015. Imaging campaigns provide new regional views, new global views at complementary lighting, high-resolution observations at pixel scales as good as <2 m/pixel in the NAC, low-light imaging of the interiors of permanently shadowed polar craters, color emission phase functions of selected features to investigate small-scale differences in photometric properties, and oblique views of high-relief features to investigate vertical structure of the upper crust. Systematic searches were conducted for Mercurian satellites and for vulcanoid asteroids whose semimajor orbital radii are interior to Mercury.

2.3.3.1              High-incidence Mapping Campaigns, Illuminated from the East and West

The high-incidence mapping from Extended Mission 1 included about a dozen large contiguous areas illuminated at high solar incidence angle from either the east or west. During the second extended mission, additional coverage at high solar incidence angle was acquired so that nearly global coverage was attained in two nearly complete, complementary global maps each at high solar incidence angles, one illuminated from the east and the other from the west.

2.3.3.2              Low-phase North Polar 5-Color Mapping Campaign

Both the 8-color global map acquired during the Primary Mission and the 3-color map acquired during Extended Mission 1 are mostly nadir-viewing, such that higher latitudes are imaged at higher phase angles. In each polar region, the high phase angles and extended shadows complicate the recognition of color variations. The northern plains surrounding the north pole are the single largest expanse of smooth plains on Mercury, and have a relatively high albedo and red color. These limitations of the 8-color and 3-color maps obscure whether there are multiple color units in the northern plains. To address this question, the northern plains region was imaged in 5 colors at a variable angle off-nadir, to attain a uniform low phase angle near 30°.

2.3.3.3              Along-track Stereo Targeted Observations

Prior to Extended Mission 2, high-resolution stereo imaging with the NAC was mostly limited to image strips taken far apart in time at complementary geometries, yielding inconsistent stereo convergence. A new approach used control of spacecraft pointing to acquire stereo geometries at two times along the spacecraft groundtrack on a single orbit, providing spatial sampling typically better than 50 m/pixel.

2.3.3.4              Dark-crater Imaging Campaigns

Beginning late in Extended Mission 1 and continuing through Extended Mission 2, the WAC clear filter and long exposures in the NAC were used to image permanently shadowed regions inside high-latitude craters, illuminated indirectly by sunlight reflected from nearby ridges or crater walls.  As of mid-2014, 3-color imaging using 560, 750, and 830 nm filters and longer exposure times began on an experimental basis.

2.3.3.5              11-color Targeted Observations

Beginning in Extended Mission 2, 11-color targets using the full set of WAC spectral filters were acquired covering regions of interest for their spectral variations, including pyroclastic vents, hollows, and fresh crater materials.

2.3.3.6              Multiple-phase Angle Observations (Emission Phase Functions)

Beginning in Extended Mission 2, 3-color targets using 430-, 750-, and 1000-nm WAC spectral filters at 2 to 5 phase angles were acquired within single orbits or groups of two orbits, to measure spatial differences in photometric properties of targets including pyroclastic vents, hollows, and fresh crater materials.

2.3.3.7              Low Flyover Movies

During Extended Mission 2, "movies" were acquired using the WAC 750-nm filter pointed into the ram direction to capture a view of flying over Mercury's surface at a low altitude.

2.3.3.8              Oblique Images

During Extended Mission 2, high emission angle views of selected high-relief features including massifs, escarpments, pyroclastic vents, and crater interiors were acquired to provide better views of exposures of vertical structure of the shallow crust.

2.3.3.9              Satellite Search

The objective of satellite searches was to observe any satellites close to opposition, when they would be at the largest solar elongation to improve brightness and detectability. Four separate searches were conducted near Mercury perihelion to enhance the brightness of the satellites, each looking northward (“upward” from the orbital apoapsis below Mercury’s south pole) toward the expected orbital plane. During each search, overlapping pointing steps were made, spanning a range from 2–75 Mercury radii. The sequence began at the greatest distance, stepped to the smallest, and then stepped back to the largest, allowing faster motion of an inner satellite to be detected (before an object left the field) while still allowing the slower motion of an outer satellite to be detected (because enough time had passed). Multiple images were used at single steps to reject radiation artifacts. Motion expected was due primarily to parallax from the spacecraft motion. The entire sequence was repeated after a fixed time. The combined searches covered ~20% of orbital phase space.

2.3.3.10          Vulcanoid Search

Due to its ability to point to 30° from the Sun at Mercury perihelion, MDIS was able to image the outer portion of the vulcanoid zone at 0.18–0.21 AU which represents 46% of the volume of the zone where vulcanoids are expected to be most likely. During MESSENGER's cruise phase, vulcanoid searches were conducted six times, collectively covering 46% of the volume of the vulcanoid zone. At each search, MDIS observed one field width north and south of the ecliptic and on both sides of the Sun. This was repeated over three time scales: immediate, to reject artifacts; after a few hours to distinguish motion from stars; and after a few days to attempt to recover an object and estimate an orbit. An altered strategy was used for two final searches from Mercury orbit, allowing detection of smaller bodies at the expense of coverage. These deeper searches were achieved by co-adding images and by making longer strings of sequential observations, thus making any motion much more prominent. Each of these searches covered 5% of the vulcanoid volume.

2.3.3.11          Nightside limb imaging

During Extended Mission 2, an experiment was conducted to attempt to image emissions from Mercury's exosphere, and to measure stellar occultations by Mercury's night-side optically. The latter was a proof-of-concept to demonstrate ability to measure the convex upper high of the seasonally shadowed portion of an asteroid during a spacecraft encounter much shorter than a Mercurian year. WAC clear filter images were acquired in sets of 3 to reject radiation noise, at three positions with the nightside of Mercury filling 0.25, 0.5, and 0.75 of the field of view. Portions of the limb were targeted where illuminated portions of the planet were at least 10° from the WAC boresight to minimize scattered light.

2.3.3.12          Other Imaging

High-resolution NAC strips, color photometry, color imaging of the south polar region, limb images, and on-orbit calibrations continued to be acquired as during the first extended mission.

2.4 Data Product Overview

The MDIS archive contains ten volumes of higher-level data products: CDRs, DDRs, BDRs, MDRs, MD3s, MP5s, HIEs, HIWs, LOIs, and RTMs. Each is briefly described below and listed in Table 2-14.  More detailed descriptions can be found in sections 3.3.5 through 3.3.14.

2.4.1 CDRs

The Calibrated Data Record (CDR) data set consists of single-frame calibrated images in units of radiance or I/F, with I/F for WAC images provided as two versions, either corrected or not corrected empirically for time-variable responsivity. CDRs are not geometrically corrected.  Versions 1 through 5 represent a series of improvements in accuracy of the radiometric calibration that reduce systematic artifacts. See section 3.3.5 for a more detailed description of the CDRs.

2.4.2 DDRs

The Derived Data Record (DDR) data set consists of single images that have 5 bands of data as 32-bit PC_REAL or IEEE_REAL: (a) latitude, (b) longitude, and (c) incidence angle, (d) emission angle, and (e) phase angle at the equipotential surface. In version 0 DDRs, latitude and longitude are calculated using the best-determined spacecraft and instrument pointing values, spacecraft position, and camera model recorded in SPICE kernels, and an ellipsoidal model of the planet surface. For version 1 DDRs, c-smithed kernels and a global digital elevation model (DEM) are used. See section 3.3.6 for a more detailed description of the DDRs.

2.4.3 BDRs

The Map Projected Basemap RDR (BDR) data set consists of a global monochrome map of reflectance corrected to i = 30ľ, e = 0ľ, g = 30ľ at a resolution of 256 pixels per degree. Version 0, released in 2013, is compiled from images taken as a part of the global monochrome basemap campaign described in section 2.3.1.1. Depending on spacecraft altitude when the data were taken, either the NAC or WAC 750-nm image was used. Version 0 is uncontrolled, projected onto an ellipsoidal model of Mercury, and photometrically corrected using a Hapke photometric model with parameters optimized to higher solar incidence angles (near 68° and different from parameters used in map products containing lower-incidence angle data). Version 1, released at end of mission, is compiled using NAC or WAC 750-nm images from any campaign that best fit the intended illumination geometry, i.e., low emission angle and incidence angle near 74°. It is controlled and projected onto a global digital elevation model. It uses a Kasseleinin-Shkuratov photometric model, whose parameters are the same for any given wavelength band across all MESSENGER end-of-mission map data products. The map is divided into 54 segments or “tiles,” each representing the NW, NE, SW, or SE quadrant of one of the 13 non-polar quadrangles, plus the 2 polar quadrangles, or “Mercury charts” already defined by the USGS (see Table 3-10). Latitude boundaries do not match precisely the USGS definition. For this archive, the equirectangular products extend to the shared midpoint latitude rather than include the defined redundant overlap between those products. Each map also contains 5 additional bands representing “backplane” data as follows: (a) observation id, (b) BDR metric, a metric used to determine the stacking order of component images – which image of all those covering  piece of terrain is "on top" (see section 2.5.2.3), (c) solar incidence angle, (d) emission angle, and (e) phase angle.  See section 3.3.7 for a more detailed description of the BDRs.

2.4.4 MDRs

The 8-color Map Projected Multispectral RDR (MDR) data set consists of a mosaicked global color map of 8-color image sets, as reflectance corrected to i = 30ľ, e = 0ľ, and g = 30° sampled at a scale of 64 pixels per degree, compiled from images taken as a part of the global 8-color map campaign described in section 2.3.1.3. Each of 54 map tiles, defined geographically in the same manner as the BDRs, is composed of 8 bands corresponding to 8 of the 11 WAC filters.  Versions 0, 1, and 2 of the map also contain 5 additional bands representing “backplane” data as follows: (a) observation id for each image set, (b) MDR metric, a metric used to determine the stacking order of component images (see section 2.5.2.3), and (c) solar incidence angle, (d) emission angle, and (e) phase angle for the 750-nm image in the set. Versions 0, 1, and 2 are uncontrolled, projected onto an ellipsoidal model of Mercury, and photometrically corrected using a Hapke photometric model with parameters optimized to lower solar incidence angles (and different from parameters used in map products containing higher-incidence angle data). Version 3 of the map, delivered at end of mission, is compiled differently. Instead of the value from any single image being used at a particular pixel location in a given wavelength band, the value used is the average from all of the images at that location where criteria for image scale, photometric geometry, and detector temperature are met. The averaging approach minimizes artifacts of time-variable instrument calibration. The 9 backplanes are redefined, and contain (a) the count of 8-color image sets at each location, and (b-j) for each wavelength band of corrected reflectance, the standard deviation to the average value. In addition, version 3 is controlled and projected onto a global digital elevation model. It uses a Kasseleinin-Shkuratov photometric model, whose parameters are the same for any given wavelength band across all MESSENGER end-of-mission map data products. For the south polar region only, there is a redundant tile having lower spatial resolution that eliminates coverage gaps present in the nominal version of the tile. See section 3.3.8 for a more detailed description of the MDRs.

2.4.5 MD3s

The 3-color Map Projected Multispectral RDR (MD3) data set consists of a mosaicked global color map of 3-color image sets, as reflectance corrected to i = 30ľ, e = 0ľ, and g = 30ľ sampled at a scale of 128 pixels per degree, compiled from images taken as a part of the regional 3-color map campaign described in section 2.3.2.3. Each map tile, defined geographically in the same manner as for BDRs and MDRs, contains 3 bands corresponding to 3 of the 11 WAC filters.  Version 0 of the map contains 5 additional bands representing “backplane” data as follows: (a) observation id for each image set, (b) the same metric as for MDRs, to determine the stacking order of component images (see section 2.5.2.3) except with the limiting spatial resolution modified, and (c) solar incidence angle, (d) emission angle, and (e) phase angle for the 750-nm image in the set. Version 0 is uncontrolled, projected onto an ellipsoidal model of Mercury, and photometrically corrected using a Hapke photometric model with parameters optimized to lower solar incidence angles (and different from parameters used in map products containing higher-incidence angle data). Version 1 of the map, delivered at end of mission, is compiled differently. Instead of the value from any single image being used at a particular pixel location in a given wavelength band, the value used is the average from all of the images at that location where criteria for image scale, photometric geometry, and detector temperature are met. The averaging approach minimizes artifacts of time-variable instrument calibration. The 4 backplanes are redefined, and contain (a) the count of 3-color image sets at each location, and (b-d) for each wavelength band of corrected reflectance, the standard deviation to the average value. In addition, version 1 is controlled and projected onto a global digital elevation model. It uses a Kasseleinin-Shkuratov photometric model, whose parameters are the same for any given wavelength band across all MESSENGER end-of-mission map data products. See section 3.3.9 for a more detailed description of the MD3s.

2.4.6 MP5s

The 5-color Map Projected Multispectral RDR (MP5) data set consists of a mosaicked regional color map of 5-color image sets, as reflectance corrected to i = 30ľ, e = 0ľ, and g = 30° sampled at a scale of 128 pixels per degree, compiled from images taken as a part of the regional 5-color map campaign described in section 2.3.3.2. There is a single map tile, the north polar tile, that contains 5 bands corresponding to 5 of the 11 WAC filters. Version 1 of the map, delivered at end of mission, is compiled using at a particular pixel location in a given wavelength band, the average from all of the images at that location where criteria for image scale, photometric geometry, and detector temperature are met. The averaging approach minimizes artifacts of time-variable instrument calibration. Six backplanes contain (a) the count of 5-color image sets at each location, and (b-f) for each wavelength band of corrected reflectance, the standard deviation to the average value. In addition, version 1 is controlled and projected onto a global digital elevation model. It uses a Kasseleinin-Shkuratov photometric model, whose parameters are the same for any given wavelength band across all MESSENGER end-of-mission map data products. See section 3.3.10 for a more detailed description of the MP5s.

2.4.7 HIEs

The Map Projected High-Incidence Angle Basemap Illuminated from the East RDR (HIE) data set consists of a global monochrome map of reflectance corrected to i = 30ľ, e = 0ľ, and g = 30° at a resolution of 256 pixels per degree, compiled from images taken as a part of the global high-incidence angle imaging campaign illuminated from the east, described in section 2.3.3.1. Each map tile, defined geographically in the same manner as for BDRs, contains a single band that merges NAC and WAC 750-nm images. Version 0 of the map also contains 5 additional bands representing “backplane” data as follows: (a) observation id, (b) the same metric as for BDRs, to determine the stacking order of component images (see section 2.5.2.3), modified for the optimal incidence angle to be 78° instead of 74°, (c) solar incidence angle, (d) emission angle, and (e) phase angle. Version 0 is uncontrolled, projected onto an ellipsoidal model of Mercury, and photometrically corrected using a Hapke photometric model with parameters optimized to higher solar incidence angles (and different from parameters used in map products containing lower-incidence angle data). Version 1, released at end of mission, is compiled using NAC or WAC 750-nm images from any campaign that best fit the intended illumination geometry, i.e., low emission angle and incidence angle near 78° with illumination from the east. It is controlled and projected onto a global digital elevation model. It uses a Kasseleinin-Shkuratov photometric model, whose parameters are the same for any given wavelength band across all MESSENGER end-of-mission map data products. See section 3.3.11 for a more detailed description of the HIEs.

2.4.8 HIWs

The Map Projected High-Incidence Angle Basemap Illuminated from the West RDR (HIW) data set consists of a global monochrome map of reflectance corrected to i = 30ľ, e = 0ľ, and g = 30° at a resolution of 256 pixels per degree, compiled from images taken as a part of the global high-incidence angle imaging campaign illuminated from the west, described in section 2.3.3.1. Each map tile, defined geographically in the same manner as for BDRs, contains a single band that merges NAC and WAC 750-nm images. Version 0 of the map also contains 5 additional bands representing “backplane” data as follows: (a) observation id, (b) the same metric as for BDRs, to determine the stacking order of component images (see section 2.5.2.3), modified for the optimal incidence angle to be 78° instead of 74°, (c) solar incidence angle, (d) emission angle, and (e) phase angle. Version 0 is uncontrolled, projected onto an ellipsoidal model of Mercury, and photometrically corrected using a Hapke photometric model with parameters optimized to higher solar incidence angles (and different from parameters used in map products containing lower-incidence angle data). Version 1, released at end of mission, is compiled using NAC or WAC 750-nm images from any campaign that best fit the intended illumination geometry, i.e., low emission angle and incidence angle near 78° with illumination from the west. It is controlled and projected onto a global digital elevation model. It uses a Kasseleinin-Shkuratov photometric model, whose parameters are the same for any given wavelength band across all MESSENGER end-of-mission map data products. See section 3.3.12 for a more detailed description of the HIWs.

2.4.9 LOIs

The Map Projected Low-Incidence Angle Basemap RDR (LOI) data set consists of a global monochrome map of reflectance corrected to i = 30ľ, e = 0ľ, and g = 30° at a resolution of 256 pixels per degree. Each map tile, defined geographically in the same manner as for BDRs, contains a single band that merges NAC and WAC 750-nm images. Each map also contains 5 additional bands representing “backplane” data as follows: (a) observation id, (b) the same metric as for MDRs, to determine the stacking order of component images (see section 2.5.2.3) except with the limiting spatial resolution modified to be the same as for BDRs, (c) solar incidence angle, (d) emission angle, and (e) phase angle. Version 1, released at end of mission, is compiled in part based on images taken as a part of the global low-incidence angle imaging campaign described in section 2.3.2.1, but it also includes any NAC or WAC 750-nm images from any campaign that best fit the intended illumination geometry, i.e., low emission angle and incidence angle near 45°. It is controlled and projected onto a global digital elevation model. It uses a Kasseleinin-Shkuratov photometric model, whose parameters are the same for any given wavelength band across all MESSENGER end-of-mission map data products. See section 3.3.13 for a more detailed description of the LOIs.

2.4.10 RTMs

The Regional Targeted Mosaic RDR (RTM) data set consists of regional maps of reflectance corrected to i = 30ľ, e = 0ľ, g = 30° at resolutions optimized to each mosaic, compiled from images taken as a part of targeted NAC strips or targeted WAC color observations. These include 4 types of targeted observations: (a) high-resolution NAC strips as described in section 2.3.1.5, (b) 3-color WAC targets as described in section 2.3.1.6, (c) 8- or 11-color WAC photometry targets as described in section 2.3.1.7, and (d) 11-color WAC targets as described in section 2.3.3.5. Each map is projected orthographically centered on the mid-point of the target, and contains 1, 3, 8, or 11 image bands depending on the type of observation (NAC or WAC 3-, 8-, or 11-color targeted observation). Each NAC mosaic also contains 4 additional bands representing "backplane" data as follows: (a) observation id, (b) solar incidence angle, (c) emission angle, and (d) phase angle. Each WAC color product contains 3 backplanes: (a) solar incidence angle, (b) emission angle, and (c) phase angle. If the observation is a WAC color observation, the additional bands are evaluated for the 750-nm filter. Version 0 is uncontrolled, projected onto an ellipsoidal model of Mercury, and photometrically corrected using a Hapke photometric model with parameters optimized to lower solar incidence angles for the WAC color mosaics and to higher solar incidence angles for the NAC mosaics. Version 1 is controlled and projected onto a global digital elevation model. It uses a Kasseleinin-Shkuratov photometric model, whose parameters are the same for any given wavelength band across all MESSENGER end-of-mission map data products. See section 3.3.14 for a more detailed description of the RTMs.

Data Product

PDS Data Set ID

Data Processing Level

Example PDS Labels

Experiment Data Record (EDR)

MESS-E/V/H-MDIS-2-EDR-V1.0

2

See EDR SIS

Calibrated Data Record (CDR)

MESS-E/V/H-MDIS-4-CDR-CALDATA-V1.0

4

Section 3.3.5

Appendix C

Derived Data Record (DDR)

MESS-E/V/H-MDIS-6-DDR-GEOMDATA-V1.0

6

Section 3.3.6

Appendix D

Map Projected Basemap RDR (BDR)

MESS-H-MDIS-5-RDR-BDR-V1.0

5

Section 3.3.7

Appendix E

8-Color Map Projected Multispectral RDR (MDR)

MESS-H-MDIS-5-RDR-MDR-V1.0

5

Section 3.3.8

Appendix F

3-Color Map Projected Multispectral RDR (MD3)

MESS-H-MDIS-5-RDR-MD3-V1.0

5

Section 3.3.9

Appendix G

5-Color Map Projected Multispectral RDR (MP5)

MESS-H-MDIS-5-RDR-MP5-V1.0

5

Section 3.3.10

Appendix H

Map Projected High-incidence Angle Basemap Illuminated from the East RDR (HIE)

MESS-H-MDIS-5-RDR-HIE-V1.0

5

Section 3.3.11

Appendix I

Map Projected High-incidence Angle Basemap Illuminated from the West RDR (HIW)

MESS-H-MDIS-5-RDR-HIW-V1.0

5

Section 3.3.12

Appendix J

Map Projected Low-incidence Angle Basemap RDR (LOI)

MESS-H-MDIS-5-RDR-LOI-V1.0

5

Section 3.3.13

Appendix K

Map Projected Regional Targeted Mosaic RDR (RTM)

MESS-H-MDIS-5-RDR-RTM-V1.0

5

Section 3.3.14

Appendix L

Table 2-14:  Definitions of MDIS data products. EDRs are not described in this document.

2.5 Data Processing

2.5.1 Data Processing Level

Data from the MESSENGER WAC and NAC are archived together.  The archive includes level 2 (and above) Committee on Data Management and Computation (CODMAC) data (Table 2-15), standard and special data products (as delineated in Applicable Document 4), and documentation describing the generation of the products.  Each MDIS data product has a unique file name and follows a specified file naming convention (see section 3.3).

 

NASA

CODMAC

Description

Packet data

Raw - Level 1

Telemetry data stream as received at the ground station, with science and engineering data embedded.

Level-0

Edited - Level 2

Instrument science data (e.g., raw voltages, counts) at full resolution, time ordered, with duplicates and transmission errors removed.

Level 1-A

Calibrated - Level 3

Level 0 data that have been located in space and may have been transformed (e.g., calibrated, rearranged) in a reversible manner and packaged with needed ancillary and auxiliary data (e.g., radiances with the calibration equations applied).

Level 1-B

Resampled - Level 4

Irreversibly transformed (e.g., resampled, remapped, calibrated) values of the instrument measurements (e.g., radiances, magnetic field strength).

Level 1-C

Derived - Level 5

Level 1A or 1B data that have been resampled and mapped onto uniform space-time grids. The data are calibrated (i.e., radiometrically corrected) and may have addi­tional corrections applied (e.g., terrain correction).

Level 2

Derived - Level 5

Geophysical parameters, generally derived from Level 1 data, and located in space and time commensurate with instrument location, pointing, and sampling.

Level 3

Derived - Level 5

Geophysical parameters mapped onto uniform space-time grids.

 

Ancillary – Level 6

Data needed to generate calibrated or resampled data sets.

Table 2-15:  Processing Levels for Science Data Sets.

 

2.5.2 Data Product Generation

MESSENGER WAC and NAC image CDRs and RDRs are produced by the MESSENGER Science Operations Center (SOC) operated jointly by APL and ACT. In some cases they are also generated by members of the MESSENGER science team. The CDRs are generated from EDRs through a data pipeline that corrects the EDRs for dark counts, flat field effects, non-linearity in response, wavelength-dependent responsivity, and time- and detector temperature-dependent variations in responsivity.

At the end of the evaluation and validation period, the data are organized and stored in the directory structure described in section 3.3, along with fiduciary checksums for transmittal to the PDS Imaging node.  The transmittal process is described in section 2.5.3.  These products are used for engineering support, direct science analysis, and construction of other science products.

2.5.2.1              CDR Generation

2.5.2.1.1                    Radiance

Laboratory and in-flight measurements were used to derive values for the terms of the calibration equation (shown in Equation 1 below) for both the WAC and NAC.  Details of how these measurements were made can be found in Hawkins et al. (2007) [Applicable Document 9].  Both instruments measure relative light intensity in engineering units referred to as data number [DN].  DNs are generally converted to radiance, L (W m-2-mm-1-sr-1), following the calibration equation:

 

                                           [1]

where: 

 

L(x,y,f,MET) is the calibrated radiance in column x, row y, through filter f measured at time MET

 

DN(x,y,f,T,t,b,MET) is the raw DN measured by the pixel in column x, row y, through filter f, at CCD temperature T and exposure time t, for binning mode b, and Mission Elapsed Time (MET),

 

Dk(x,y,T,t,b) is the dark level in a given pixel, derived either from the dark strip or estimated from exposure time and CCD temperature,

 

Sm(x,y,t,b) is the scene-dependent frame transfer smear for the pixel,

 

Flat(x,y,f,b)  is the non-uniformity or “flat-field” correction at this pixel location,

 

Resp(f,T,b) is temperature-dependent responsivity, relating dark-, flat-, and smear-corrected DN per unit exposure time to radiance,

 

t is the exposure time in milliseconds.

2.5.2.1.2                    I/F

To convert from radiance to I/F (also known as radiance factor, the ratio of measured radiance to that which would be measured from a white perfectly Lambertian surface), which is used to populate CDRs, the following expression should be applied:

I_over_F(x,y,f,MET) = L(x,y,f,MET) / Correct(f,MET) * pi * (SOLAR_DISTANCE/149597870.691)^2 / F(f)                                                                       [2]

where:

L(x,y,f,MET) is calibrated radiance calculated as described above for some filter f at some time MET

SOLAR_DISTANCE is that value for distance of the target object from the center of the Sun in kilometers (as indicated by the keyword SOLAR_DISTANCE),

149597870.691 is the number of kilometers in 1 AU, and

F(f) is effective average solar irradiance at 1 AU sampled under the filter bandpass (Table 2-16).

For the NAC, Correct(f,MET) is unity and only one version of I/F is generated, with the character string "IF" in the file name. For the WAC, two versions of I/F are generated, with (IF) and without (IU) an empirical correction for time-varying responsivity, Correct(f,MET) which is described by Denevi et al. (2016) [Applicable Document 14].

2.5.2.1.3                    Treatment of special pixels

Two types of pixels in an EDR cannot be validly calibrated to either radiance or I/F:

Š       Pixels under the dark mask at the edge of the detector do not measure light from the scene, yet deviation of their calibrated value from zero is a valuable measure of calibration residuals. The average calibrated value under the dark mask is reported in the label as DARK_STRIP_MEAN, but the actual pixel values are replaced by the value indicated in the label for CORE_NULL.

Š       Saturated pixels do not have a known correspondence to scene radiance. The pixel values in saturated pixels are replaced by the value indicated in the label for CORE_HIGH_INSTR_SATURATION.

These keywords are discussed further in Appendix B.

 


 

Imager

Filter Number

Band Center, nm

Bandwidth, nm

Solar Irradiance, W m-2 Ķm-1

NAC

N/A

747.70

 52.55

1278.85

WAC

   1
 698.76
  5.30
1429.10
   2
 701.27
196.51
1432.13
   3
 479.87
 10.14
2091.95
   4
 558.91
  5.82
1833.26
   5
 628.81
  5.52
1669.08
   6
 433.21
 18.11
1733.07
   7
 748.73
  5.09
1293.93
   8
 947.03
  6.15
 813.27
   9
 996.23
 14.30
 741.46
  10
 898.80
  5.08
 900.80
  11
1012.56
 33.33
 714.15
  12
 828.39
  5.20
1062.92

Table 2-16:  Solar irradiance used to convert radiance to units of I/F.

 

2.5.2.2              DDR Generation

The sequence of processing that creates a DDR is as follows.  Gimbal positions are extracted from the gimbal C kernel.  Using that and other SPICE kernels, the equipotential surface intercept is calculated for each spatial pixel.  The angles of this pixel relative to the equatorial plane and reference longitude constitute the latitude and longitude of the pixel.  For that latitude and longitude, solar incidence, emission, and phase angles are determined.

2.5.2.3              BDR, MDR, MD3, MP5, HIE, HIW, LOI, and RTM Generation

The sequence of processing that creates a BDR, MDR, MD3, MP5, HIE, HIW, LOI, or RTM from CDRs and DDRs (Figure 2-17) is as follows:

(a) EDRs are assembled from raw data.

(b) Radiance images are created from the EDRs and calibration files.

(c) Radiance is converted to I/F CDRs by dividing by (empiricalcorrection * pi * solar flux at 1 AU * heliocentricdistance^2).

(d) I/F is converted to reflectance through a photometric correction to i = 30ľ, e = 0ľ, g=30°. Early versions of these products used a Hapke correction; the final versions used a Kasseleinen-Shkuratov correction as described by Domingue et al. (2016) [Applicable Document 13].

(e) Gimbal positions are extracted from the spacecraft housekeeping and formatted as a gimbal C kernel.

(f) Using the gimbal C kernel and other SPICE kernels, DDRs are created. The surface intercept on Mercury's surface is calculated for each spatial pixel. The angles of this pixel relative to the equatorial plane and reference longitude constitute the latitude and longitude of the pixel. For that latitude and longitude, solar incidence, emission, and phase angles are determined at an equipotential surface. For version 0 DDRs, latitude and longitude are calculated using the best-determined spacecraft and instrument pointing values, spacecraft position, and camera model recorded in SPICE kernels, and an ellipsoidal model of the planet surface. For version 1 DDRs, c-smithed kernels and a global digital elevation model (DEM) are used, with the DEM derived using a least-squares bundle adjustment of common features, measured as tie point coordinates in overlapping NAC and WAC-G filter images, as described by Becker et al. (2016) [Applicable Document 15].

(g) Reflectance corrected to i = 30ľ, e = 0ľ, g=30° from the WAC and/or NAC is map projected into multiband map products using the latitude and longitude information in the DDRs. The same procedure is used on DDRs to assemble the backplanes with derived information.

Prior to the final delivery of products at end of mission, all map products used data from simple mapping campaigns, and a stacking order to determine “which image is on top”. For the end-of-mission delivery, regional or global multispectral maps (MDRs/MD3s/MP5s) employed an averaging procedure using all overlapping images at a given latitude and longitude where criteria for image scale, photometric geometry, and detector temperature are met. The averaging approach minimizes artifacts of time-variable instrument calibration. Also, end-of-mission products mixed images from different campaigns to more closely approach desired lighting geometries or to fill gaps.

Separate stacking orders (“which image is on top”) are defined for BDRs/HIEs/HIWs and for MDRs/MD3s/MP5s/LOIs. Which images were taken as part of the basemap or color mapping campaigns represented by these data products is indicated within an observation table used internally at the MESSENGER Science Operations Center.

For BDRs, the objective is to have “on top” those images with high spatial resolution, low emission angle, and a solar incidence angle as close as possible to 68° (version 0, 74° for version 1). This incidence angle was defined as an optimum that minimizes shadows while including topographic shading. Any image taken as part of the basemap campaign is a candidate to include in BDRs. The stacking order is determined by evaluating at the camera boresight a metric that represents both spatial resolution and image geometry; lowest values for the metric represent the “best” image. The “worst” complete, map-projected image with the highest value for the metric is laid into the BDR first; then the complete image with the second-highest value is laid in second, overwriting the first image where the coverage coincides, and so on until the complete “best” image with the lowest value for the metric is on top. Where abs(lat) ≤ 65° and i ≥ NN°, the metric is:

PIXEL_SCALE / (cos e * ( cos ( flatten_factor * i)  / cos ( flatten_factor * NN ) ) )

where i is solar incidence angle, e is emission angle, lat is planetocentric latitude, and flatten_factor is set to 0.85 to de-emphasize low solar incidence angles. Where abs(lat) ≤ 65° and i < NN°, the metric is:

PIXEL_SCALE / (cos e * (cos NN / cos i))

Where abs(lat) > 65°, the metric is:

PIXEL_SCALE / (cos i * cos e )

In either case, values for PIXEL_SCALE less than 166 meters are reset to 166 meters. In version 0 BDRs, NN is 68° and in version 1 BDRs NN is 74°.

The stacking order for HIEs and HIWs parallels that for BDRs, except that the "crossover" solar incidence angle (which tends to be "on top") is 78° instead of 68° or 74°.

For MDRs, MD3s, MP5s, and LOIs, the objective is to have “on top” those images with high spatial resolution, low emission angle, and low solar incidence angle. Any image taken as part of one of these mapping campaigns is a candidate to include in the corresponding product set. The stacking order is determined in a fashion comparable to that used for BDRs, with some modifications. If the sequence includes multiple WAC filters, rather than complete images being map-projected and laid into the mosaics, only a portion of each image is used, in which the same region of Mercury is observing in all filters of the color sequence. The image quality metric is evaluated at the camera boresight of the middle image in that sequence; lowest values represent the “best” image. For each color sequence or image taken as part of the low-incidence campaign, the “worst” image or part of a sequence with overlapping coverage in all filters (highest value of the metric) is map-projected and laid into the data product first; then the image or overlap region with the second-highest value is laid in second, overwriting the first overlap region, and so on until the “best” image or overlap region with the lowest metric is on top. At all latitude and solar incidence angles, the metric is:

PIXEL_SCALE / (cos i * cos e )

where for MDRs values for PIXEL_SCALE less than 665 meters are reset to 665 meters, for MD3s and MP5 values for PIXEL_SCALE less than 332 meters are reset to 332 meters, and for LOIs values for PIXEL_SCALE less than 166 meters are reset to 166 meters.

Description: Description: Description: Description: data_flow_MDIS_20120425_revised

Figure 2-17:  Sequential processing of EDRs to yield RDRs, showing roles of CDRs and DDRs. BDRs and MDRs are shown as examples but the same flow yields MD3s, MP5s, HIEs, HIWs, LOIs, or RTMs.

 

2.5.3 Data Flow and Transmittal to PDS

The MESSENGER Science Operations Center (SOC) operates under the auspices of the MESSENGER Project Scientist to plan data acquisition and generate and validate data archives.  The SOC supports and works with the Mission Operations Center (MOC), the Science Team, instrument scientists, and the PDS.

 

The SOC is located at JHU/APL.  The SOC produces early versions of products that can be used by the science and instrument teams.  They are of the same type, content, and format as the final science products with default information for unknown data such as pointing and spacecraft housekeeping.

 

At the end of the evaluation and validation period, the data are organized and stored in the directory structure described in section 3.3, along with fiduciary checksums.  This directory structure is compressed into a single “zip archive” file for transmittal to the PDS imaging node.  The zip archive preserves the directory structure internally so that when it is decompressed the original directory structure is recreated at the PDS node.  The zip archive is transmitted to the PDS node via FTP to a specified URL.

2.5.4 Transmittal Time Line

Several MDIS archive releases, as detailed in the MESSENGER Data Management and Archiving Plan [Applicable Document 4], are assembled and transmitted to PDS.  At least two weeks before the deadline for transmittal, the zip archive file is transmitted to the PDS node.  At the same time, a letter of transmittal is sent which provides a record of the fiduciary checksums provided in the archive file itself.  Within several days of transmittal, the node acknowledges receipt (but not verification) of the archive and letter of transmittal.  If acknowledgement is not received, or if problems are reported, the MESSENGER SOC immediately takes corrective action to affect successful transmittal.

After transmittal, the PDS node uncompresses the zip archive file and independently calculates the fiduciary checksums for each file.  The calculated checksums are compared to the checksums in the transmittal letter and those recorded in the archive itself.  The node then performs any additional verification and validation of the data provided and reports any discrepancies or problems to the MESSENGER SOC.  Typically the node performs these checks and inspections in about two weeks.  After inspection is completed to the satisfaction of the PDS node, the node issues to the MESSENGER SOC acknowledgement of successful receipt.

2.6 Standards Used in Generating Data Products

2.6.1 PDS Standards

The MDIS data products comply with the PDS standards for file formats and labels, specifically the PDS image and table data objects [Applicable Documents 2 and 3].  Please see Appendix A for definitions of PDS data archive terms.

2.6.2 Time Standards

Two time standards are used in MDIS data products:

Š         spacecraft time in seconds (PDS label keywords SPACECRAFT_CLOCK_START_-COUNT and SPACECRAFT_CLOCK_STOP_COUNT)

Š         UTC (PDS label keywords START_TIME, STOP_TIME, and PRODUCT_CREA-TION_TIME)

2.6.3 Coordinate Systems

The following bulleted list outlines the computational assumptions for the geometric and viewing data provided in the PDS label.  There are two coordinate systems in use: 1) the celestial reference system used for target and spacecraft position and velocity vectors, and camera pointing; and 2) the planetary coordinate system for geometry vectors and target location.  The celestial coordinate system is J2000 (Mean of Earth equator and equinox of J2000).  The planetary coordinate system is planetocentric with respect to a reference ellipsoid. Through the final, end-of-mission products, the assumed ellipsoid is a sphere with 2440 km radius; in end-of-mission products, the sphere is 2439.4 km.

 

COMPUTATIONAL ASSUMPTIONS

Š         The mid-point time of an observation is used for the geometric element computations.

Š         Label parameters reflect observed, not true, geometry. Therefore, light-time and stellar aberration corrections are needed as appropriate.

Š         The inertial reference frame is J2000 (also called EME2000).

Š         Target body latitudes and longitudes are planetocentric.  The initial agreed upon Mercury ellipsoid is a sphere with a 2440 km radius; the sphere used at end of mission is 2439.4 km in radius.

Š         The "sub-point" of a spacecraft on a target body is defined by the surface intercept of the spacecraft-to-target-body-center vector.  This point is not necessarily the closest point on the target body to the spacecraft.  This definition gives sub-point latitude and longitude that are independent of the target’s reference ellipsoid.

Š         Distances are in km, speeds in km/sec, angles in degrees.

Š         Angular rates in degrees/sec, unless otherwise noted.

Š         Angle ranges are 0 to 360 degrees for azimuths and local hour angle.  Longitudes range from 0 to 360 degrees (positive to the East).  Latitudes range from -90 to 90 degrees.

2.6.4 Data Storage Conventions

The data are organized following PDS standards and transferred to the PDS for distribution to the science community.  Data will be stored under unique file names as defined in Section 3.3.

2.7 Data Validation

Data validation falls into two types, validation of the science data and validation of the compliance of the archive with PDS archiving and distribution requirements.  The first type of validation is carried out by the Science Team, and the second is overseen by the PDS, in coordination with the Science Team.

The formal validation of data content, adequacy of documentation, and adherence to PDS archiving and distribution standards is subject to an external peer review.  Peer reviews are scheduled and coordinated by the PDS.  The peer review process may result in "liens," actions recommended by the reviewers or by PDS personnel to correct the archive.  All liens must be resolved by the dataset provider: the SOC for Level 1 data, and the Science Team for higher-level data products, calibration data, and calibration algorithms.  Once the liens are cleared, PDS does a final validation prior to packaging and delivery.

The SOC periodically reports results of validation to the MESSENGER Science Steering Committee.  If the volumes are approved for release by the Project, then the SOC will transfer the archives to the PDS [Applicable Document 4].


3. DETAILED DATA PRODUCT SPECIFICATIONS

3.1 Data Product Structure and Organization

Data that comprise the MESSENGER Image Archive are formatted according to the standards of the Planetary Data System, as documented in the PDS Standards Reference manual [Applicable Document 3].  Archive-quality data sets include everything needed to understand and utilize the data.  The raw images by themselves are insufficient for the science community to realize the full scientific potential of the data.  Thus, the MESSENGER project provides as part of the archive the ancillary data to perform radiometric, photometric, and cartographic processing.  Additionally, a documentation set is provided to describe the data products, imaging instruments, and mission operations.

3.2 Geometric Elements

Geometric elements fully describe the viewing geometry of each observation.  The geometric elements are organized according to the SPICE kernel concepts adopted by the Navigational Ancillary Information Facility (NAIF) at the Jet Propulsion Laboratory.  SPICE is an acronym for Spacecraft, Planet, Instrument, C-matrix, and Event kernels (see http://naif.jpl.nasa.gov).

SPICE kernels evolve and improve as further analysis is done.  The PDS data labels attached to the image data products are based on the most up-to-date SPICE information available at the time of product creation.

3.3 Archive Volume Structure and Contents

This section describes the contents of the MDIS Archive volumes, including the file names, file contents, file types, and organization responsible for providing the files.  The indication that a file is required means that it is required by the PDS standards for archive volumes, as specified in the PDS Standards Reference, Applicable Document 3.  See Appendix A for definitions of data archive terms.

There are ten separate CDR/RDR volumes, one for each of the ten CDR/RDR product types.  The volumes bear the PDS-assigned volume IDs MSGRMDS_2001, MSGRMDS_3001, MSGRMDS_4001, MSGRMDS_5001, MSGRMDS_6001, MSGRMDS_7001, MSGRMDS_7101, MSGRMDS_7201, MSGRMDS_7301, and MSGRMDS_8001 for the CDRs, DDRs, BDRs, MDRs, MD3s, HIEs, HIWs, LOIs, MP5s, and RTMs respectively.  An MDIS archive volume will contain the following directories below the root.  The first five are always present, if applicable (the CALIB directory is only relevant to the EDR, CDR, MDR, MD3, MP5, and RTM volumes).  BROWSE and EXTRAS are populated on a best-effort basis.

Š         INDEX

Š         CATALOG

Š         DOCUMENT

Š         DATA (named CDR, DDR, BDR, MDR, MD3, MP5, HIE, HIW, LOI, or RTM based on product type)

Š         CALIB

Š         BROWSE

Š         EXTRAS

3.3.1 Root Directory

Files in the Root Directory (Table 3-1) include an overview of the archive, a description of the volume for the PDS Catalog, and a list of errata or comments about the archive.  The following files are contained in the Root Directory.

 

File Name

Required?

File Contents

AAREADME.TXT

Yes

General information file.  Provides users with an overview of the contents and organization of the associated volume, general instructions for its use, and contact information.

ERRATA.TXT

No

Text file for identifying and describing errors and/or anomalies found in the current volume, and possibly previous volumes of a set.  Any known errors for the associated volume will be documented in this file.

VOLDESC.CAT

Yes

PDS file containing the VOLUME object.  This gives a high-level description of the contents of the volume. Information includes: production date, producer name and institution, volume ID, etc.

Table 3-1:  Root Directory Contents.

 

3.3.2 Index Directory

Files in the Index Directory (Table 3-2) are provided to help the user locate products on the archive volume.  The following files are contained in the Index Directory.

File Name

Required?

File Contents

INDXINFO.TXT

Yes

Identifies and describes the function of each file in the index subdirectory.  This includes a description of the structure and contents of the index table and usage notes.

INDEX.TAB

Yes

The image index file is organized as a table: there is a row for each image on the volume; the columns contain parameters that describe the observation and camera states of the images. Information includes viewing geometry (such as latitude and longitude of the image center, sun and observation angles) and camera state information such as filter wheel position, spacecraft clock count, time of observation, image integration time, and camera modes.

INDEX.LBL

Yes

Detached PDS label for INDEX.TAB that describes its organization and contents.

MD5.TAB

No

The checksum table is a listing of all files in the archive (with the exception of the checksum table itself) that gives the MD5 checksum (message digest) for the file and the full path including file name. It is generated by the commonly available "MD5Deep" utility. This file is useful as a manifest for the archive and for data integrity assurance.

MD5.LBL

 

Detached PDS label for MD5.TAB.

Table 3-2:  Index Directory Contents.

 

Tables 3-3 and 3-4 list the columns in the CDR/DDR and BDR/MDR/MD3/MP5/HIE/HIW/ LOI/RTM index files, respectively.  They are the most significant keywords pulled from labels of the various products.  The lists are comprehensive in the sense that they include the important keywords for all data products.  For any given data product, some of the fields are inapplicable and are set to N/A.

Column

Format

CDR Example

VOLUME_ID

CHARACTER

MSGRMDS_2001

PATH_NAME

CHARACTER

“CDR/2007_156”

FILE_NAME

CHARACTER

“CW089570568G_RA_0.IMG”

PRODUCT_ID

CHARACTER

“CW0089570568G_RA_0”

OBSERVATION_ID

CHARACTER

“6747”

DATA_QUALITY_ID

CHARACTER

“0000001000000000”

MISSION_PHASE_NAME

CHARACTER

"VENUS 2 FLYBY"

TARGET_NAME

CHARACTER

VENUS

SEQUENCE_NAME

CHARACTER

“07156_APP_WAC_MOSAIC_1”

PRODUCT_CREATION_TIME

TIME

2007-11-13T23:30:37

START_TIME

TIME

2007-06-05T22:40:41.702888

STOP_TIME

TIME

2007-06-05T22:40:41.768887

SPACECRAFT_CLOCK_START_COUNT

CHARACTER

“1/0089570568:950000”

SPACECRAFT_CLOCK_STOP_COUNT

CHARACTER

“1/0089570568:990000”

INSTRUMENT_ID

CHARACTER

"MDIS-WAC"

FILTER_NUMBER

ASCII_INTEGER

7

CENTER_FILTER_WAVELENGTH

ASCII_INTEGER

750 <NM>

EXPOSURE_DURATION

ASCII_INTEGER

66  <MS>

EXPOSURE_TYPE

CHARACTER

AUTO

DETECTOR_TEMPERATURE

ASCII_REAL

-39.86  <degC>

FOCAL_PLANE_TEMPERATURE

ASCII_REAL

-20.19  <degC>

FILTER_TEMPERATURE

ASCII_REAL

-20.66  <degC>

OPTICS_TEMPERATURE

ASCII_REAL

-20.85  <degC>

MESS:PIV_POS

ASCII_INTEGER

9007

MESS:PIV_POS_MOTOR

ASCII_INTEGER

1000

MESS:PIV_READ

ASCII_INTEGER

9007

MESS:FPU_BIN

ASCII_INTEGER

0

MESS:COMP12_8

ASCII_INTEGER

0

MESS:COMP_ALG

ASCII_INTEGER

2

MESS:COMP_FST

ASCII_INTEGER

1

MESS:WVLRATIO

ASCII_INTEGER

4

MESS:PIXELBIN

ASCII_INTEGER

0

MESS:SUBFRAME

ASCII_INTEGER

0

RETICLE_POINT_RA_1

ASCII_REAL

182.77358 <DEG>

RETICLE_POINT_RA_2

ASCII_REAL

172.41885 <DEG>

RETICLE_POINT_RA_3

ASCII_REAL

181.37369 <DEG>

RETICLE_POINT_RA_4

ASCII_REAL

170.89950 <DEG>

RETICLE_POINT_DECLINATION_1

ASCII_REAL

0.76231 <DEG>

RETICLE_POINT_DECLINATION_2

ASCII_REAL

2.21637 <DEG>

RETICLE_POINT_DECLINATION_3

ASCII_REAL

-9.59692 <DEG>

RETICLE_POINT_DECLINATION_4

ASCII_REAL

-8.12579 <DEG>

SPACECRAFT_SOLAR_DISTANCE

ASCII_REAL

108040911.97274 <KM>

SLANT_DISTANCE

ASCII_REAL

14090.89871 <KM>

CENTER_LATITUDE

ASCII_REAL

35.73941 <DEG>

CENTER_LONGITUDE

ASCII_REAL

226.54464 <DEG>

HORIZONTAL_PIXEL_SCALE

ASCII_REAL

2530.43332 <M>

SMEAR_MAGNITUDE

ASCII_REAL

10.38328 <PIXELS>

RETICLE_POINT_LATITUDE_1

ASCII_REAL

“N/A”

RETICLE_POINT_LATITUDE_2

ASCII_REAL

47.22207 <DEG>

RETICLE_POINT_LATITUDE_3

ASCII_REAL

24.61941 <DEG>

RETICLE_POINT_LATITUDE_4

ASCII_REAL

20.95210 <DEG>

RETICLE_POINT_LONGITUDE_1

ASCII_REAL

“N/A”

RETICLE_POINT_LONGITUDE_2

ASCII_REAL

244.79392 <DEG>

RETICLE_POINT_LONGITUDE_3

ASCII_REAL

208.68936 <DEG>

RETICLE_POINT_LONGITUDE_4

ASCII_REAL

239.57209 <DEG>

SOLAR_DISTANCE

ASCII_REAL

108040911.97274 <KM>

SUB_SOLAR_AZIMUTH

ASCII_REAL

11.49500 <DEG>

SUB_SPACECRAFT_LATITUDE

ASCII_REAL

14.91164 <DEG>

SUB_SPACECRAFT_LONGITUDE

ASCII_REAL

246.92915 <DEG>

SPACECRAFT_ALTITUDE

ASCII_REAL

13114.84420 <KM>

SUB_SOLAR_LATITUDE

ASCII_REAL

-1.29302 <DEG>

SUB_SOLAR_LONGITUDE

ASCII_REAL

283.86863 <DEG>

INCIDENCE_ANGLE

ASCII_REAL

64.85698 <DEG>

PHASE_ANGLE

ASCII_REAL

30.69683 <DEG>

EMISSION_ANGLE

ASCII_REAL

39.19187 <DEG>

DARK_STRIP_MEAN

ASCII_REAL

7.81804628787e-05

MINIMUM

ASCII_REAL

7.81804628787e-05

MAXIMUM

ASCII_REAL

0.1620197892189

MEAN

ASCII_REAL

0.032525319648508

STANDARD_DEVIATION

ASCII_REAL

0.029913486227533

SATURATED_PIXEL_COUNT

ASCII_REAL

      0

Table 3-3:  CDR/DDR Index Table Contents.

 

Column

Format

BDR Example

VOLUME_ID

CHARACTER

MSGRMDS_4001

PATH_NAME

CHARACTER

BDR/H03/

FILE_ NAME

CHARACTER

“MDIS_BDR_200PPD_H03NE.IMG”

PRODUCT_ID

CHARACTER

“MDIS_BDR_200PPD_H03NE”

SITE_NAME (RTM only)

CHARACTER

"Degas_South_Ray_NAC_Strip_2"

PRODUCT_CREATION_TIME

TIME

2011-10-25T23:17:20.029

START_TIME

TIME

9999-01-01T01:01:01

STOP_TIME

TIME

9999-01-01T01:01:01

PRODUCT_VERSION_ID

ASCII_INTEGER

1

LINES

ASCII_INTEGER

6400

LINE_SAMPLES

ASCII_INTEGER

9216

BANDS

ASCII_INTEGER

2

MAP_PROJECTION_TYPE

CHARACTER

"EQUIRECTANGULAR"

CENTER_LATITUDE

ASCII_REAL

0.0000000 <DEGREE>

CENTER_LONGITUDE

ASCII_REAL

0.000000 <DEGREE>

MAP_SCALE

ASCII_REAL

212.930169 <M/PIXEL>

MAP_RESOLUTION

ASCII_INTEGER

200 <PIXEL/DEGREE>

LINE_PROJECTION_OFFSET

ASCII_REAL

13000.000003

SAMPLE_PROJECTION_OFFSET

ASCII_REAL

3250.637830

MAXIMUM_LATITUDE

ASCII_REAL

25.0000000 <DEGREE>

MINIMUM_LATITUDE

ASCII_REAL

0.0000000 <DEGREE>

WESTERNMOST_LONGITUDE

ASCII_REAL

0.0000000 <DEGREE>

EASTERNMOST_LONGITUDE

ASCII_REAL

36.0000000 <DEGREE>

Table 3-4:  BDR/MDR/MD3/MP5/HIE/HIW/LOI/RTM Index Table Contents.

 

3.3.3 Catalog Directory

The files in the Catalog Directory (Table 3-5) provide a top-level understanding of the mission, spacecraft, instruments, and data set.  The files in this directory become part of the PDS Catalog to provide background information for the user searching for data.  Their format and contents are further specified in the PDS Standards Reference (Applicable Document 3).  The following files are found in the Catalog Directory.

File Name

Required?

File Contents

CATINFO.TXT

Yes

Identifies and describes the function of each file in the catalog directory.

MDIS_NNN_DS.CAT

Yes

Data set description, where NNN is replaced by CDR, DDR, BDR, MDR, MD3, MP5, HIE, HIW, LOI, or RTM.

INSTHOST.CAT

Yes

Description of the MESSENGER spacecraft for the PDS catalog.

MDIS_NAC_INST.CAT
MDIS_WAC_INST.CAT

Yes

Description of the MDIS NAC and WAC.

NNN_MAP.CAT

Yes

MDIS data set map projection information, where NNN is replaced by BDR, MDR, MD3, HIE, HIW, LOI, or RTM (not applicable to CDR, DDR, or MP5).

NNN_POLAR_MAP.CAT

Yes

MDIS data set map projection information for polar regions, where NNN is replaced by BDR, MDR, MD3, MP5, HIE, HIW, or LOI (not applicable to CDR, DDR, or RTM).

MISSION.CAT

Yes

Description of the MESSENGER mission.

PERSON.CAT

Yes

List of personnel associated with the MESSENGER PDS delivery.

TARGET.CAT

Yes

List of astronomical and planetary targets in the images.

REF.CAT

Yes

Catalog objects’ citation list for the PDS catalog.

Table 3-5:  Catalog Directory Contents.

 


3.3.4 Document Directory

The Document Directory (Table 3-6) contains documentation to help the user understand and use the archive data.  The following files are contained in the Document Directory.

File Name

Required?

File Contents

DOCINFO.TXT

Yes

Identifies and describes the function of each file in the document directory.

MDIS_CDR_RDRSIS.DOC

Yes

Software Interface Specification for the CDR/RDR data products as a Microsoft Word document.

MDIS_CDR_RDRSIS.PDF

Yes

Software Interface Specification for the CDR/RDR data products as an Adobe PDF document.

MDIS_CDR_RDRSIS.HTM

Yes

Software Interface Specification for the CDR/RDR data products as an HTML document.

MDIS_CDR_RDRSIS.LBL

Yes

PDS label for MDIS_CDR_RDRSIS.DOC, MDIS_CDR_RDRSIS.PDF and MDIS_CDR_RDRSIS.HTM.

PDSDD.FUL

No

PDS data dictionary. Includes definitions of all keywords used in MESSENGER data labels.

Table 3-6:  Document Directory Contents.

 

3.3.5 CDR Directory (CDR Volumes Only)

3.3.5.1              CDR File Naming

The file names developed for this PDS archive are restricted to a maximum 36-character base name and 3 character extension name with a period separating the file and extension names.  Also known as the “36.3” format, this is compliant with the ISO 9660 Level 2 specification (maximum of 40 characters), which is required by PDS.  The MDIS CDR products have an “18.3” format and thus remain within the PDS specification parameters.  Below is the detailed naming convention for this dataset.

 

Format:  "pcrnnnnnnnnnf_tt_v"

 

p = product type = C calibrated

c = camera (W WAC or N NAC)

r = spacecraft-clock-partition-number minus 1 [0, 1] for pre- or post-spacecraft-clock-reset

nnnnnnnnn = Mission Elapsed Time (MET) counter taken from the image header (and same as original compressed filename from SSR).  NOTE: this is a spacecraft clock seconds counter, and the value in the filename corresponds to the LAST second of the exposure.

f = Filter wheel position (A, B, C, D, E, F, G, H, I, J, K, L, U) for the WAC (see Table 3-7 below).  It is M for the NAC, which has no filter wheel.  It will be U if the position is unknown.

tt = data type (RA radiance, IF I/F, or IU I/F in the WAC if uncorrected empirically for time-variations in responsivity)

v = version number

 

The following is an example file name with a description of the individual components:

 

Filter Number

Filter Filename Letter

Wavelength (Flight)

(nm)

Width (Flight)

(nm)

1

A

698.8

5.3

2

B

700

600.0

3

C

479.9

10.1

4

D

558.9

5.8

5

E

628.8

5.5

6

F

433.2

18.1

7

G

748.7

5.1

8

H

947.0

6.2

9

I

996.2

14.3

10

J

898.8

5.1

11

K

1012.6

33.3

12

L

828.4

5.2

Table 3-7:  Filter numbers and their bandpasses.

 

CW0014032676F_RA_0.IMG

 

For this image:

Š         Product type = CDR (C)

Š         Camera = WAC (W)

Š         Clock partition = 1 (pre-clock reset)

Š         MET = 014032676

Š         WAC filter wheel position = 6 (433nm/18 nm FWHM) (F)

Š         Data type = radiance (RA)

Š         Version number = 0

3.3.5.2              CDR Structure and Organization

A Calibrated Data Record (CDR) is a single image that has been corrected for geometric and optical effects.  The MDIS CDR data set consists of files that parallel Experiment Data Records (EDRs) in their format and directory structure.  Each attached label points to a single-frame calibrated image in units of radiance or I/F as 32-bit PC_REAL or IEEE_REAL. 

x, y dimensions = 1024/(MESS:FPU_BIN * MESS:PIXELBIN)

See section 2.5.2.1 for a description of how the CDR products are generated.

3.3.5.3              CDR Label Description

The label area of the data file conforms to PDS version 3.8 standards (Applicable Document 3).  The purpose of the PDS label is to describe the measurement data and provide engineering and observation parameters.  A sample CDR label can be found in Appendix C.  Table 3-8 below lists MDIS-specific values for CDR label keywords.  See Appendix B for keyword descriptions.

As a result of an August 2009 flight software update, all MDIS CDRs were regenerated and redelivered to PDS with Release 5 (March 15, 2010).  The keywords OBSERVATION_ID, MESS:IMG_ID_LSB, MESS:IMG_ID_MSB, and MESS:PIV_POS_MOTOR were added to the CDR labels with this update.  CDRs from Mercury Flyby 2 and earlier have values of “N/A” for these keywords.  The keyword MESS:PIV_GOAL is set to “N/A” after Mercury Flyby 2.

Keyword

Valid Values

INSTRUMENT_NAME

“MERCURY DUAL IMAGING SYSTEM WIDE ANGLE CAMERA”

“MERCURY DUAL IMAGING SYSTEM NARROW ANGLE CAMERA”

INSTRUMENT_ID

“MDIS-WAC”

“MDIS-NAC”

OBSERVATION_TYPE

"Albedo"

"Monochrome,Oblique"

"Albedo,Albedo Stereo"

"Monochrome,Ridealong NAC"

"Co-align Calibration"

"Monochrome,Stereo"

"Color"

"Monochrome,Targeted"

"Color,Emission Phase Function"

"N/A"

"Color,Southern Polar"

"NAC WAC Calibration"

"Color,Targeted"

"Northern Polar"

"Color,Targeted,Photometry"

"Pivot Calibration"

"Comet"

"Satellite Search"

"Dark Current"

"Southern Polar"

"Dark Polar Craters"

"Southern Polar,Eleven Color"

"Eleven Color,NAC WAC Calibration"

"Stereo,Targeted"

"Engineering"

"Targeted,Eleven Color"

"High Incidence"

"Targeted,Photometry,Eleven Color"

"Limb"

"Thermal Calibration"

"Min Phase Five Color"

"Three Color"

"Monochrome"

"Vulcanoid Search"

FILTER_NAME

"430 BP 40", "430 BW 40"

"480 BP 10", "480 BW 10"

"560 BP 5", "560 BW 5"

"630 BP 5", "630 BW 5"

"700 BP 5", "700 BW 5"

"750 BP 5", "750 BW 5"

"830 BP 5", "830 BW 5"

"900 BP 5", "900 BW 5"

"950 BP 7", "950 BW 7"

"1000 BP 15", "1000 BW 15"

"1020 BP 40", "1020 BW 40"

“N/A”

FILTER_NUMBER

Integer 1 - 12

“N/A”

MESS:EC_FACTOR

Empirical correction factor, Correct(f,MET) from the calibration equation in section 2.5.2.1.2. "N/A" for NAC, real number or "N/A" for WAC

MESS:MET_EXP

Time in seconds

MESS:IMG_ID_LSB

Integer 0 to 65535

MESS:IMG_ID_MSB

Integer 0 to 255

MESS:ATT_CLOCK_COUNT

Time in seconds

MESS:ATT_Q1

-1.0 to 1.0

MESS:ATT_Q2

-1.0 to 1.0

MESS:ATT_Q3

-1.0 to 1.0

MESS:ATT_Q4

-1.0 to 1.0

MESS:ATT_FLAG

Integer 0 to 7

MESS:PIV_POS_MOTOR

Integer 0 to 65535

MESS:PIV_GOAL

Integer -32768 to 32768

MESS:PIV_POS

Integer -32768 to 32768

MESS:PIV_READ

Integer 0 to 65535

MESS:PIV_CAL

Integer -32768 to 32768

MESS:FW_GOAL

Integer 0 to 65535

MESS:FW_POS

Integer 0 to 65535

MESS:FW_READ

Integer 0 to 65535

MESS:CCD_TEMP

Integer 0 to 4095

MESS:CAM_T1

Integer 0 to 1023

MESS:CAM_T2

Integer 0 to 1023

MESS:EXPOSURE

Time in seconds

MESS:DPU_ID

Integer 0 or 1

MESS:IMAGER

Integer 0 or 1

MESS:SOURCE

Integer 0, 1, or 2

MESS:FPU_BIN

Integer 0 or 1

MESS:COMP12_8

Integer 0 or 1

MESS:COMP_ALG

Integer 0 to 7

MESS:COMP_FST

Integer 0 or 1

MESS:TIME_PLS

Integer 0 to 3

MESS:LATCH_UP

Integer 0 or 1

MESS:EXP_MODE

Integer 0 or 1

MESS:PIV_STAT

Integer 0 to 3

MESS:PIV_MPEN

Integer 0 or 1

MESS:PIV_PV

Integer 0 or 1

MESS:PIV_RV

Integer 0 or 1

MESS:FW_PV

Integer 0 or 1

MESS:FW_RV

Integer 0 or 1

MESS:AEX_STAT

Integer 0 to 4095

MESS:AEX_STHR

Integer 0 to 65535

MESS:AEX_TGTB

Integer 0 to 4095

MESS:AEX_BACB

Integer 0 to 4095

MESS:AEX_MAXE

Integer 0 to 989

MESS:AEX_MINE

Integer 0 to 989

MESS:DLNKPRIO

Integer 0 to 9

MESS:WVLRATIO

Integer 0 to 32

MESS:PIXELBIN

Integer 0, 2, 4, or 8

MESS:SUBFRAME

Integer 0 to 5

MESS:SUBF_X1

Integer 0 to 1023

MESS:SUBF_Y1

Integer 0 to 1023

MESS:SUBF_DX1

Integer 0 to 1024

MESS:SUBF_DY1

Integer 0 to 1024

MESS:SUBF_X2

Integer 0 to 1023

MESS:SUBF_Y2

Integer 0 to 1023

MESS:SUBF_DX2

Integer 0 to 1024

MESS:SUBF_DY2

Integer 0 to 1024

MESS:SUBF_X3

Integer 0 to 1023

MESS:SUBF_Y3

Integer 0 to 1023

MESS:SUBF_DX3

Integer 0 to 1024

MESS:SUBF_DY3

Integer 0 to 1024

MESS:SUBF_X4

Integer 0 to 1023

MESS:SUBF_Y4

Integer 0 to 1023

MESS:SUBF_DX4

Integer 0 to 1024

MESS:SUBF_DY4

Integer 0 to 1024

MESS:SUBF_X5

Integer 0 to 1023

MESS:SUBF_Y5

Integer 0 to 1023

MESS:SUBF_DX5

Integer 0 to 1024

MESS:SUBF_DY5

Integer 0 to 1024

MESS:CRITOPNV

Integer 0 or 1

MESS:JAILBARS

Integer 0 or 1

MESS:JB_X0

Integer 0 to 1023

MESS:JB_X1

Integer 0 to 1023

MESS:JB_SPACE

Integer 0 to 1023

Table 3-8.  MDIS-specific values for CDR label keywords.

 

3.3.6 DDR Directory (DDR Volumes Only)

3.3.6.1              DDR File Naming

The file names developed for this PDS archive are restricted to a maximum 36-character base name and 3 character extension name with a period separating the file and extension names.  Also known as the “36.3” format, this is compliant with the ISO 9660 Level 2 specification (maximum of 40 characters), which is required by PDS.  The MDIS DDR products have a “18.3” format and thus remain within the PDS specification parameters.  Below is the detailed naming convention for this dataset.

Format:  "pcrnnnnnnnnnf_tt_v"

 

p = product type = D derived

c = camera (W WAC or N NAC)

r = spacecraft-clock-partition-number minus 1 [0, 1] for pre- or post-spacecraft-clock-reset nnnnnnnnn = Mission Elapsed Time (MET) counter taken from the image header (and same as original compressed filename from SSR).  NOTE: this a spacecraft clock seconds counter, and the value in the filename corresponds to the LAST second of the exposure.

f = Filter wheel position (A, B, C, D, E, F, G, H, I, J, K, L, U) for the WAC (see Table 3-7 above).  It is M for the NAC, which has no filter wheel.  It will be U if the position is unknown.

tt = data type (RA radiance, IF I/F, or DE derived products)

v = version number

 

The following is an example file name with a description of the individual components:

 

DW0089570568F_DE_0.IMG

 

For this image:

Š         Product type = DDR (D)

Š         Camera = WAC (W)

Š         Clock partition = 1 (pre-clock reset)

Š         MET = 089570568

Š         WAC filter wheel position = 6 (419nm/44 nm FWHM) (F)

Š         Data type = derived (DE)

Š         Version number = 0

 

3.3.6.2              DDR Structure and Organization

The Derived Data Record (DDR) data set consists of files that parallel CDRs in their directory structure.  Each DDR has 5 layers of data containing geometric information (latitude, longitude, incidence angle, emission angle, phase angle).  This information is derived from pixel spatial coordinates and associated SPICE files.  A DDR label is attached and points to a single multiband image in the DDR.

x, y dimensions = 1024/(MESS:FPU_BIN * MESS:PIXELBIN)

See section 2.5.2.2 for a description of how the DDR products are generated.

3.3.6.3              DDR Label Description

The label conforms to PDS version 3.8 standards (Applicable Document 3).  The purpose of the PDS label is to describe the measurement data and provide engineering and observation parameters.  A sample DDR label can be found in Appendix D.  Table 3-9 below lists MDIS-specific values for DDR label keywords.  See Appendix B for keyword descriptions.

 

Keyword

Valid Values

INSTRUMENT_NAME

“MERCURY DUAL IMAGING SYSTEM WIDE ANGLE CAMERA”

“MERCURY DUAL IMAGING SYSTEM NARROW ANGLE CAMERA

INSTRUMENT_ID

“MDIS-WAC”

“MDIS-NAC”

FILTER_NAME

"430 BP 40", "430 BW 40"

"480 BP 10", "480 BW 10"

"560 BP 5", "560 BW 5"

"630 BP 5", "630 BW 5"

"700 BP 5", "700 BW 5"

"750 BP 5", "750 BW 5"

"830 BP 5", "830 BW 5"

"900 BP 5", "900 BW 5"

"950 BP 7", "950 BW 7"

"1000 BP 15", "1000 BW 15"

"1020 BP 40", "1020 BW 40"

“N/A”

OBSERVATION_TYPE

"Albedo"

"Monochrome,Oblique"

"Albedo,Albedo Stereo"

"Monochrome,Ridealong NAC"

"Color"

"Monochrome,Stereo"

"Color,Emission Phase Function"

"Monochrome,Targeted"

"Color,Southern Polar"

"NAC WAC Calibration"

"Color,Targeted"

"Northern Polar"

"Color,Targeted,Photometry"

"Southern Polar"

"Dark Polar Craters"

"Southern Polar,Eleven Color"

"Eleven Color,NAC WAC Calibration"

"Stereo,Targeted"

"High Incidence"

"Targeted,Eleven Color"

"Limb"

"Targeted,Photometry,Eleven Color"

"Min Phase Five Color"

"Three Color"

"Monochrome"

 

FILTER_NUMBER

Integers 1 - 12

“N/A”

MESS:MET_EXP

Time in seconds

MESS:IMG_ID_LSB

Integer 0 to 65535

MESS:IMG_ID_MSB

Integer 0 to 255

MESS:ATT_CLOCK_COUNT

Time in seconds

MESS:ATT_Q1

-1.0 to 1.0

MESS:ATT_Q2

-1.0 to 1.0

MESS:ATT_Q3

-1.0 to 1.0

MESS:ATT_Q4

-1.0 to 1.0

MESS:ATT_FLAG

Integer 0 to 7

MESS:PIV_POS_MOTOR

Integer 0 to 65535

MESS:PIV_GOAL

Integer -32768 to 32768

MESS:PIV_POS

Integer -32768 to 32768

MESS:PIV_READ

Integer 0 to 65535

MESS:PIV_CAL

Integer -32768 to 32768

MESS:FW_GOAL

Integer 0 to 65535

MESS:FW_POS

Integer 0 to 65535

MESS:FW_READ

Integer 0 to 65535

MESS:CCD_TEMP

Integer 0 to 4095

MESS:CAM_T1

Integer 0 to 1023

MESS:CAM_T2

Integer 0 to 1023

MESS:EXPOSURE

Time in seconds

MESS:DPU_ID

Integer 0 or 1

MESS:IMAGER

Integer 0 or 1

MESS:SOURCE

Integer 0, 1, or 2

MESS:FPU_BIN

Integer 0 or 1

MESS:COMP12_8

Integer 0 or 1

MESS:COMP_ALG

Integer 0 to 7

MESS:COMP_FST

Integer 0 or 1

MESS:TIME_PLS

Integer 0 to 3

MESS:LATCH_UP

Integer 0 or 1

MESS:EXP_MODE

Integer 0 or 1

MESS:PIV_STAT

Integer 0 to 3

MESS:PIV_MPEN

Integer 0 or 1

MESS:PIV_PV

Integer 0 or 1

MESS:PIV_RV

Integer 0 or 1

MESS:FW_PV

Integer 0 or 1

MESS:FW_RV

Integer 0 or 1

MESS:AEX_STAT

Integer 0 to 4095

MESS:AEX_STHR

Integer 0 to 65535

MESS:AEX_TGTB

Integer 0 to 4095

MESS:AEX_BACB

Integer 0 to 4095

MESS:AEX_MAXE

Integer 0 to 989

MESS:AEX_MINE

Integer 0 to 989

MESS:DLNKPRIO

Integer 0 to 9

MESS:WVLRATIO

Integer 0 to 32

MESS:PIXELBIN

Integer 0, 2, 4, or 8

MESS:SUBFRAME

Integer 0 to 5

MESS:SUBF_X1

Integer 0 to 1023

MESS:SUBF_Y1

Integer 0 to 1023

MESS:SUBF_DX1

Integer 0 to 1024

MESS:SUBF_DY1

Integer 0 to 1024

MESS:SUBF_X2

Integer 0 to 1023

MESS:SUBF_Y2

Integer 0 to 1023

MESS:SUBF_DX2

Integer 0 to 1024

MESS:SUBF_DY2

Integer 0 to 1024

MESS:SUBF_X3

Integer 0 to 1023

MESS:SUBF_Y3

Integer 0 to 1023

MESS:SUBF_DX3

Integer 0 to 1024

MESS:SUBF_DY3

Integer 0 to 1024

MESS:SUBF_X4

Integer 0 to 1023

MESS:SUBF_Y4

Integer 0 to 1023

MESS:SUBF_DX4

Integer 0 to 1024

MESS:SUBF_DY4

Integer 0 to 1024

MESS:SUBF_X5

Integer 0 to 1023

MESS:SUBF_Y5

Integer 0 to 1023

MESS:SUBF_DX5

Integer 0 to 1024

MESS:SUBF_DY5

Integer 0 to 1024

MESS:CRITOPNV

Integer 0 or 1

MESS:JAILBARS

Integer 0 or 1

MESS:JB_X0

Integer 0 to 1023

MESS:JB_X1

Integer 0 to 1023

MESS:JB_SPACE

Integer 0 to 1023

BAND_NAME

"Latitude, planetocentric, deg N"
"Longitude, planetocentric, deg E"
"Incidence angle at equipotential surface, deg"
"Emission angle at equipotential surface, deg"
"Phase angle at equipotential surface, deg"

Table 3-9.  MDIS-specific values for DDR label keywords.

3.3.7 BDR Directory (BDR Volumes Only)

MDIS near-nadir NAC and WAC 750-nm filter imaging of Mercury with incidence angles near 68° (version 0, 74° for version 1) is mosaicked into 54 non-overlapping, 256 pixel/degree tiles (BDRs). Each tile corresponds to the NW, NE, SW, or, SE quadrant of one of the pre-existing Mercury non-polar charts or one of the two polar charts. Version 0 contains only data from the basemap imaging campaign; version 1 contains data with appropriate illumination from any campaign.

3.3.7.1              BDR File Naming

The file names developed for this PDS archive are restricted to a maximum 36-character base name and 3 character extension name with a period separating the file and extension names.  Also known as the “36.3” format, this is compliant with the ISO 9660 Level 2 specification (maximum of 40 characters), which is required by PDS.  The MDIS BDR products have a “22.3” format and thus remain within the PDS specification parameters.  Below is the detailed naming convention for this dataset.

Map tiles are named based on the quadrant of the Mercury chart they span.

 

Format:  "MDIS_ppp_rrrPPD_Hxxddv.ext"

 

ppp = product type = BDR

rrr = resolution in pixels/degree (PPD)

Hxx = Mercury chart designation

dd = quadrant within Mercury chart (NW, NE, SW, or SE), or a polar chart (NP, SP)

v = version number

ext = IMG for the multiband image, LBL for the detached label

 

The following is an example file name with a description of the individual components:

 

MDIS_BDR_256PPD_H03NE0.IMG

 

For this image:

Š         Product type = BDR (BDR)

Š         Resolution = 256 pixels/degree (256PPD)

Š         Mercury chart = Shakespeare (H03)

Š         Quadrant = Northeast (NE)

Š         Version = 0

 

3.3.7.2              BDR Structure and Organization

The BDR directory, present in the BDR archive volume, contains MDIS Map Projected Basemap Reduced Data Records (BDRs).  The BDRs are organized into subdirectories based on the Mercury Chart containing the BDR.  Latitude and longitude limits of Mercury Charts and the corresponding subdirectory names are given in Table 3-10.

Quadrangle1

Subdirectory name

Latitude (degrees)

Longitude (deg. east)

H-1 Borealis

H01

65 to 90

0 to 360

H-2 Victoria

H02

22.5 to 65

270 to 360

H-3 Shakespeare

H03

22.5 to 65

180 to 270

H-4 Raditladi (Liguria)

H04

22.5 to 65

90 to 180

H-5 Hokusai (Apollonia)

H05

22.5 to 65

0 to 90

H-6 Kuiper

H06

-22.5 to 22.5

288 to 360

H-7 Beethoven

H07

-22.5 to 22.5

216 to 288

H-8 Tolstoj

H08

-22.5 to 22.5

144 to 216

H-9 Eminescu (Solitudo Criophori)

H09

-22.5 to 22.5

72 to 144

H-10 Derain (Pieria)

H10

-22.5 to 22.5

0 to 72

H-11 Discovery

H11

-65 to -22.5

270 to 360

H-12 Michelangelo

H12

-65 to -22.5

180 to 270

H-13 Neruda (Solitudo Persephones)

H13

-65 to -22.5

90 to 180

H-14 Debussey (Cyllene)

H14

-65 to -22.5

0 to 90

H-15 Bach

H15

-90 to -65

0 to 360

Table 3-10. Latitude and longitude limits of Mercury Charts.
1Parenthetical names are defunct for quadrangles not imaged by a spacecraft prior to MESSENGER.

 

A BDR:

Š         Consists of a mosaic of map-projected, photometrically normalized I/F CDRs collectively forming a monochrome map tile.

Š         Contains image data in I/F corrected photometrically to i=30°, e=0°, g=30° sampled at a scale of 256 pixels per degree (~166 meters/pixel at the equator), composed of WAC filter 7 (G) (750 BP 5) and NAC images.

Š         Represents one latitude-longitude bin in a global map. 

Š         Contains 5 backplanes for the reference 750-nm band: (a) observation id, (b) BDR metric, (c) solar incidence angle, (d) emission angle, and (e) phase angle.  “BDR metric” is a metric describing the resolution and illumination of data used to determine where and whether to overlay future imaging coverage (see section 2.5.2.3).

 

Versions increment on reprocessing or addition of new data.  Polar tiles are in polar stereographic projections, other tiles in equirectangular projection.

See section 2.5.2.3 for a description of how the BDR products are generated.

3.3.7.3              BDR Map Projection Standards 

The projection convention adopted by the MESSENGER project is planetocentric and positive east. Prior to delivery 15, the MESSENGER team used the prime meridian and other Mercury coordinate system values described in Archinal et al. [2009, Applicable Document 12] with Mercury radii of 2440 km for products provided to PDS. For delivery 15, the MESSENGER team used the Mercury coordinate system values contained in the SPICE Planetary Constants Kernel provided to NAIF by MESSENGER with delivery 15 which included updates to the Mercury prime meridian, rotation rate, and radii (2439.4 km). The projection varies with latitude, using EQUIRECTANGULAR for tiles centered equatorward of 65 degrees latitude, and POLAR STEREOGRAPHIC centered poleward of 65 degrees latitude.

Equirectangular Projections

For the latitude band projected equirectangularly, the CENTER_LATITUDE of projection is the equatorward boundary of each band to minimize 'distortion.'  The transformation from line and sample coordinates to planetocentric latitude and longitude is given by these equations.

            x = (SAMPLE - SAMPLE_PROJECTION_OFFSET - 0.5) * MAP_SCALE

            y = (LINE - LINE_PROJECTION_OFFSET - 0.5) * -1 * MAP_SCALE

            lat = y / (A_AXIS_RADIUS * 1000)

            lon = CENTER_LONGITUDE +

              180/pi * (x/(A_AXIS_RADIUS * 1000 * cos(CENTER_LATITUDE*pi/180))

Note that integral values of line and sample correspond to the center of a pixel. Lat and lon are the latitude and longitude of a given location on the surface, east positive.

            MAP_SCALE= the map scale in meters per pixel, approximately 166.3 meters/pixel for a BDR, which achieves close to the desired 256 pixels/degree at the CENTER_LATITUDE.

            LINE_PROJECTION_OFFSET = the line offset value of the map projection origin from the line and sample 1,1 (line and sample 1,1 is considered the upper left corner of the digital array). For an EQUIRECTANGULAR map projection, origin is the equatorward edge of the map tile. The value of LINE_PROJECTION_OFFSET is positive for images starting north of the equator and is negative for images starting south of the equator.

            SAMPLE_PROJECTION_OFFSET = the sample offset value of the map projection origin from line and sample 1,1 (line and sample 1,1 is considered the upper left corner of the digital array).  For an EQUIRECTANGULAR map projection, the value of SAMPLE_PROJECTION_OFFSET is positive for images starting to the west of the projection longitude and is negative for images starting to the east of the projection longitude.

            MAP_RESOLUTION is measured in pixels/degree.

There are four PDS parameters that specify the latitude and longitude boundaries of an image. MAXIMUM_LATITUDE and MINIMUM_LATITUDE specify the latitude boundaries of the image, and EASTERNMOST_LONGITUDE and WESTERNMOST_LONGITUDE specify the longitudinal boundaries of the map.

Definitions of other mapping parameters can be found in the PDS Data Dictionary.

Polar Stereographic Projections

For the latitude bands projected polar stereographically, projection is centered on the north or south pole. Lines of longitude extend radially from the pole and parallels of latitude are concentric circles around the center. In the north, longitude 0 extends straight down from the center and longitude 90 East extends to the right. In the south, longitude 0 extends straight up from the center, and longitude 90 East extends to the right. Thus in any given tile, north is at a variable orientation in LINE-SAMPLE space. The transformation from line and sample coordinates to planetocentric latitude and longitude is given by these equations.

            x = (SAMPLE - SAMPLE_PROJECTION_OFFSET - 0.5) * MAP_SCALE

            y = (LINE - LINE_PROJECTION_OFFSET - 0.5) * -1 * MAP_SCALE

            rho = sqrt(x^2 + y^2)

              (if rho=0, lat,lon is the reference pole)

            c = 2 * atan(rho/(2*(A_AXIS_RADIUS*1000)))

            lon = CENTER_LONGITUDE + (atan2(x,-y) * 180/pi) (northern hemisphere)

            lon = CENTER_LONGITUDE + (atan2(x,y) * 180/pi) (southern hemisphere)

            lat = 180/pi *     arcsin[cos(c)*sin(CENTER_LATITUDE*pi/180) +

              (y*sin(c)*cos(CENTER_LATITUDE*pi/180)/rho)]

where lat = latitude in degrees and lon = longitude in degrees.

            LINE_PROJECTION_OFFSET = the line offset value of the map projection origin from the line and sample 1,1 (line and sample 1,1 is considered the upper left corner of the digital array).

            SAMPLE_PROJECTION_OFFSET = the sample offset value of the map projection origin from line and sample 1,1 (line and sample 1,1 is considered the upper left corner of the digital array).

            MAP_SCALE is measured in m/pixel.

There are four PDS parameters that specify the latitude and longitude boundaries of an image.  MAXIMUM_LATITUDE and MINIMUM_LATITUDE specify the latitude boundaries of the image, and EASTERNMOST_LONGITUDE and WESTERNMOST_LONGITUDE specify the longitudinal boundaries of the map.

Definitions of other mapping parameters can be found in the PDS Data Dictionary.

3.3.7.4              BDR Label Description

The detached label conforms to PDS version 3.8 standards (Applicable Document 3).  The purpose of the PDS label is to describe the data product. A single label points to the IMG file. Sample BDR labels can be found in Appendix E.  Table 3-11 below lists MDIS-specific values for BDR label keywords.  See Appendix B for keyword descriptions.

Keyword

Valid Values

INSTRUMENT_ID

“MDIS-WAC”

“MDIS-NAC”

PRODUCT_TYPE

MAP_PROJECTED_BDR

UNIT

“Reflectance”

BAND_NAME

“REFLECTANCE 750NM”

“OBSERVATION ID”

“BDR METRIC”

"SOLAR INCIDENCE ANGLE"

"EMISSION ANGLE"

"PHASE ANGLE”

Table 3-11.  MDIS-specific values for BDR label keywords. Reflectance is at i=30°, e=0°, g=30°.

3.3.8 MDR Directory (MDR Volumes Only)

MDIS 8-color imaging of Mercury is mosaicked into 54 non-overlapping, 64 pixel/degree tiles (MDRs). Each tile corresponds to the NW, NE, SW, or SE quadrant of one of the pre-existing Mercury non-polar charts, or one of the two polar charts.

3.3.8.1              MDR File Naming

The file names developed for this PDS archive are restricted to a maximum 36-character base name and 3 character extension name with a period separating the file and extension names.  Also known as the “36.3” format, this is compliant with the ISO 9660 Level 2 specification (maximum of 40 characters), which is required by PDS.  The MDIS MDR products have a “22.3” format and thus remain within the PDS specification parameters.  Below is the detailed naming convention for this dataset.

Map tiles will be named based on the quadrant of the Mercury chart they span. The nominal version of each tile is named as follows.

 

Format:  "MDIS_ppp_rrrPPD_Hxxddv.ext"

 

ppp = product type = MDR

rrr = resolution in pixels/degree (PPD)

Hxx = Mercury chart designation

dd = quadrant within Mercury chart (NW, NE, SW, or SE), or a polar chart (NP, SP)

v = version number

ext = IMG for the multiband image, LBL for the detached label

 

The following is an example file name with a description of the individual components:

 

MDIS_MDR_064PPD_H03NE0.IMG

 

For this image:

Š         Product type = MDR (MDR)

Š         Resolution = 64 pixels/degree (064PPD)

Š         Mercury chart = Shakespeare (H03)

Š         Quadrant = Northeast (NE)

Š         Version = 0

 

A redundant tile covering the south polar region has a modified nomenclature, reflecting that it includes reduced-resolution (to 2700 m/pixel) images in order to fill a coverage gap in the nominal tile.

 

MDIS_MDR_064PPD_2700_H15SP1.IMG

 

3.3.8.2              MDR Structure and Organization

The MDR directory, present in the MDR archive volume, contains 8-color MDIS Map Projected Multispectral Reduced Data Records (MDRs).  The MDRs are organized into subdirectories based on the Mercury Chart containing the MDR.  Latitude and longitude limits of Mercury Charts and the corresponding subdirectory names are given in Table 3-10.

An MDR:

Š         Consists of a mosaic of map-projected, photometrically normalized I/F CDRs collectively forming a multispectral map tile.

Š         Contains image data in I/F corrected photometrically to i=30°, e=0°, g=30° at a resolution of 64 pixels per degree (~665 m/pixel at the equator).

Š         Represents one latitude-longitude bin in a global color map. 

Š         Is composed of up to 8 bands corresponding to the 8 of the 11 WAC filters. The 8 are selected on account of limitations in MESSENGER solid-state recorder space, and more or less evenly sample the spectral range of MDIS.

Š         Version 0, 1 or 2 contains 5 backplanes for the reference 750-nm band: (a) observation id, (b) MDR metric, (c) solar incidence angle, (d) emission angle, and (e) phase angle.  “MDR metric” is a metric describing the resolution and illumination of data used to determine where and whether to overlay future imaging coverage (see section 2.5.2.3).

Š         Version 3 contains 9 backplanes for the reference 750-nm band: (a) image count, and (b-i) standard deviation of the values used to determine average normalized I/F in each of the 8 bands (see section 2.5.2.3).

 

Versions increment on reprocessing or addition of new data.  Polar tiles are in polar stereographic projections, other tiles in equirectangular projection.

See section 2.5.2.3 for a description of how the MDR products are generated.

 

3.3.8.3              MDR Map Projection Standards

The projection convention adopted by the MESSENGER project is planetocentric and positive east. Prior to delivery 15, the MESSENGER team used the prime meridian and other Mercury coordinate system values described in Archinal et al. [2009, Applicable Document 12] with Mercury radii of 2440 km for products provided to PDS. For delivery 15, the MESSENGER team used the Mercury coordinate system values contained in the SPICE Planetary Constants Kernel provided to NAIF by MESSENGER with delivery 15 which included updates to the Mercury prime meridian, rotation rate, and radii (2439.4 km). The projection varies with latitude, using EQUIRECTANGULAR for tiles centered equatorward of 65 degrees latitude, and POLAR STEREOGRAPHIC centered poleward of 65 degrees latitude.

Equirectangular Projections

For the latitude band projected equirectangularly, the CENTER_LATITUDE of projection is the equatorward boundary of each band to minimize 'distortion.'  The transformation from line and sample coordinates to planetocentric latitude and longitude is given by these equations.

            x = (SAMPLE - SAMPLE_PROJECTION_OFFSET - 0.5) * MAP_SCALE

            y = (LINE - LINE_PROJECTION_OFFSET - 0.5) * -1 * MAP_SCALE

            lat = y / (A_AXIS_RADIUS * 1000)

            lon = CENTER_LONGITUDE +

              180/pi * (x/(A_AXIS_RADIUS * 1000 * cos(CENTER_LATITUDE*pi/180))

Note that integral values of line and sample correspond to the center of a pixel. Lat and lon are the latitude and longitude of a given location on the surface, east positive.

            MAP_SCALE= the map scale in meters per pixel, approximately 665.3 meters/pixel for an MDR, which achieves close to the desired 64 pixels/degree at the CENTER_LATITUDE.

            LINE_PROJECTION_OFFSET = the line offset value of the map projection origin from the line and sample 1,1 (line and sample 1,1 is considered the upper left corner of the digital array). For an EQUIRECTANGULAR map projection, origin is the equatorward edge of the map tile. The value of LINE_PROJECTION_OFFSET is positive for images starting north of the equator and is negative for images starting south of the equator.

            SAMPLE_PROJECTION_OFFSET = the sample offset value of the map projection origin from line and sample 1,1 (line and sample 1,1 is considered the upper left corner of the digital array). For an EQUIRECTANGULAR map projection, the value of SAMPLE_PROJECTION_OFFSET is positive for images starting to the west of the projection longitude and is negative for images starting to the east of the projection longitude.

            MAP_RESOLUTION is measured in pixels/degree.

There are four PDS parameters that specify the latitude and longitude boundaries of an image. MAXIMUM_LATITUDE and MINIMUM_LATITUDE specify the latitude boundaries of the image, and EASTERNMOST_LONGITUDE and WESTERNMOST_LONGITUDE specify the longitudinal boundaries of the map.

Definitions of other mapping parameters can be found in the PDS Data Dictionary.

Polar Stereographic Projections

For the latitude bands projected polar stereographically, projection is centered on the north or south pole. Lines of longitude extend radially from the pole and parallels of latitude are concentric circles around the center. In the north, longitude 0 extends straight down from the center and longitude 90 East extends to the right. In the south, longitude 0 extends straight up from the center, and longitude 90 East extends to the right. Thus in any given tile, north is at a variable orientation in LINE-SAMPLE space. The transformation from line and sample coordinates to planetocentric latitude and longitude is given by these equations.

            x = (SAMPLE - SAMPLE_PROJECTION_OFFSET - 0.5) * MAP_SCALE

            y = (LINE - LINE_PROJECTION_OFFSET - 0.5) * -1 * MAP_SCALE

            rho = sqrt(x^2 + y^2)

              (if rho=0, lat,lon is the reference pole)

            c = 2 * atan(rho/(2*(A_AXIS_RADIUS*1000)))

            lon = CENTER_LONGITUDE + (atan2(x,-y) * 180/pi) (northern hemisphere)

            lon = CENTER_LONGITUDE + (atan2(x,y) * 180/pi) (southern hemisphere)

            lat = 180/pi *     arcsin[cos(c)*sin(CENTER_LATITUDE*pi/180) +

              (y*sin(c)*cos(CENTER_LATITUDE*pi/180)/rho)]

where lat = latitude in degrees and lon = longitude in degrees.

            LINE_PROJECTION_OFFSET = the line offset value of the map projection origin from the line and sample 1,1 (line and sample 1,1 is considered the upper left corner of the digital array).

            SAMPLE_PROJECTION_OFFSET = the sample offset value of the map projection origin from line and sample 1,1 (line and sample 1,1 is considered the upper left corner of the digital array).

            MAP_SCALE is measured in m/pixel.

There are four PDS parameters that specify the latitude and longitude boundaries of an image.  MAXIMUM_LATITUDE and MINIMUM_LATITUDE specify the latitude boundaries of the image, and EASTERNMOST_LONGITUDE and WESTERNMOST_LONGITUDE specify the longitudinal boundaries of the map.

Definitions of other mapping parameters can be found in the PDS Data Dictionary.

 

3.3.8.4              MDR Label Description

The detached label conforms to PDS version 3.8 standards (Applicable Document 3).  The purpose of the PDS label is to describe the data product. A single label points to the IMG file. Sample MDR labels can be found in Appendix F.  Table 3-12 below lists MDIS-specific values for MDR label keywords.  See Appendix B for keyword descriptions.

Keyword

Valid Values

INSTRUMENT_ID

“MDIS-WAC”

PRODUCT_TYPE

MAP_PROJECTED_MDR

UNIT

“Reflectance”

BAND_NAME

Version 0 or 1:

"WAC FILTER 6 430 BP 40"

"WAC FILTER 3 480 BP 10"

"WAC FILTER 4 560 BP 5"

"WAC FILTER 5 630 BP 5"

"WAC FILTER 7 750 BP 5"

"WAC FILTER 12 830 BP 5"

"WAC FILTER 10 900 BP 5"

"WAC FILTER 9 1000 BP 15"

Version 0:

“OBSERVATION ID”

“MDR METRIC”

"SOLAR INCIDENCE ANGLE"

"EMISSION ANGLE"

"PHASE ANGLE”

Version 1:

"IMAGE COUNT"

"STDEV WAC FILTER 6 430 BP 40"

"STDEV WAC FILTER 3 480 BP 10"

"STDEV WAC FILTER 4 560 BP 5"

"STDEV WAC FILTER 5 630 BP 5"

"STDEV WAC FILTER 7 750 BP 5"

"STDEV WAC FILTER 12 830 BP 5"

"STDEV WAC FILTER 10 900 BP 5"

"STDEV WAC FILTER 9 1000 BP 15"

Table 3-12.  MDIS-specific values for MDR label keywords. Reflectance is at i=30°, e=0°, g=30°.

 

3.3.9 MD3 Directory (MD3 Volumes Only)

The 3-color MDIS image mosaic of Mercury's northern and equatorial latitudes is divided into non-overlapping, 128 pixel/degree tiles (MD3s). Each tile corresponds to the NW, NE, SW, or SE quadrant of one of the pre-existing Mercury non-polar charts, or the north polar chart.

3.3.9.1              MD3 File Naming

The file names developed for this PDS archive are restricted to a maximum 36-character base name and 3 character extension name with a period separating the file and extension names.  Also known as the “36.3” format, this is compliant with the ISO 9660 Level 2 specification (maximum of 40 characters), which is required by PDS.  The MDIS MD3 products have a “22.3” format and thus remain within the PDS specification parameters.  Below is the detailed naming convention for this dataset.

Map tiles are named based on the quadrant of the Mercury chart they span.

 

Format:  "MDIS_ppp_rrrPPD_Hxxddv.ext"

 

ppp = product type = MD3

rrr = resolution in pixels/degree (PPD)

Hxx = Mercury chart designation

dd = quadrant within Mercury chart (NW, NE, SW, or SE), or a polar chart (NP, SP)

v = version number

ext = IMG for the multiband image, LBL for the detached label

 

The following is an example file name with a description of the individual components:

 

 

MDIS_MD3_128PPD_H03NE0.IMG

 

For this image:

Š         Product type = MD3 (MD3)

Š         Resolution = 128 pixels/degree (128PPD)

Š         Mercury chart = Shakespeare (H03)

Š         Quadrant = Northeast (NE)

Š         Version = 0

 

3.3.9.2              MD3 Structure and Organization

The MD3 directory, present in the MD3 archive volume, contains 3-color MDIS Map Projected Multispectral Reduced Data Records (MD3s).  The MD3s are organized into subdirectories based on the Mercury Chart containing the MDR.  Latitude and longitude limits of Mercury Charts and the corresponding subdirectory names are given in Table 3-10. For MD3s there is no H15 subdirectory because the 3-color mapping campaign did not include that portion of Mercury.

An MD3:

Š         Consists of an uncontrolled mosaic of map-projected, photometrically normalized I/F CDRs collectively forming a multispectral map tile.

Š         Contains image data in I/F corrected photometrically to i=30°, e=0°, g=30° at a resolution of 128 pixels per degree (~332 m/pixel at the equator).

Š         Represents one latitude-longitude bin in a regional color map. 

Š         Is composed of up 3 bands corresponding to 3 of the 11 WAC filters. The 3 sample albedo and spectral slope variations over the spectral range of MDIS; the fewer filters than in the 8-color map is for data volume management during acquisition, due to spatial sampling >2 times smaller in scale.

Š         Version 0 contains 5 backplanes for the reference 750-nm band: (a) observation id, (b) MDR metric, (c) solar incidence angle, (d) emission angle, and (e) phase angle.  “MDR metric” is a metric describing the resolution and illumination of data used to determine where and whether to overlay future imaging coverage (see section 2.5.2.3), modified for the different limiting spatial resolution.

Š         Version 1 contains 4 backplanes for the reference 750-nm band: (a) image count, and (b-d) standard deviation of the values used to determine average normalized I/F in each of the 3 bands (see section 2.5.2.3).

 

Versions increment on reprocessing or addition of new data.  Polar tiles are in polar stereographic projections, other tiles in equirectangular projection.

See section 2.5.2.3 for a description of how the MDR products are generated.

 

3.3.9.3              MD3 Map Projection Standards

The projection convention adopted by the MESSENGER project is planetocentric and positive east. Prior to delivery 15, the MESSENGER team used the prime meridian and other Mercury coordinate system values described in Archinal et al. [2009, Applicable Document 12] with Mercury radii of 2440 km for products provided to PDS. For delivery 15, the MESSENGER team used the Mercury coordinate system values contained in the SPICE Planetary Constants Kernel provided to NAIF by MESSENGER with delivery 15 which included updates to the Mercury prime meridian, rotation rate, and radii (2439.4 km). The projection varies with latitude, using EQUIRECTANGULAR for tiles centered equatorward of 65 degrees latitude, and POLAR STEREOGRAPHIC centered poleward of 65 degrees latitude.

Equirectangular Projections

For the latitude band projected equirectangularly, the CENTER_LATITUDE of projection is the equatorward boundary of each band to minimize 'distortion.'  The transformation from line and sample coordinates to planetocentric latitude and longitude is given by these equations.

            x = (SAMPLE - SAMPLE_PROJECTION_OFFSET - 0.5) * MAP_SCALE

            y = (LINE - LINE_PROJECTION_OFFSET - 0.5) * -1 * MAP_SCALE

            lat = y / (A_AXIS_RADIUS * 1000)

            lon = CENTER_LONGITUDE +

              180/pi * (x/(A_AXIS_RADIUS * 1000 * cos(CENTER_LATITUDE*pi/180))

Note that integral values of line and sample correspond to the center of a pixel. Lat and lon are the latitude and longitude of a given location on the surface, east positive.

            MAP_SCALE= the map scale in meters per pixel, approximately 332.7 meters/pixel for an MD3, which achieves close to the desired 128 pixels/degree at the CENTER_LATITUDE.

            LINE_PROJECTION_OFFSET = the line offset value of the map projection origin from the line and sample 1,1 (line and sample 1,1 is considered the upper left corner of the digital array). For an EQUIRECTANGULAR map projection, origin is the equatorward edge of the map tile. The value of LINE_PROJECTION_OFFSET is positive for images starting north of the equator and is negative for images starting south of the equator.

            SAMPLE_PROJECTION_OFFSET = the sample offset value of the map projection origin from line and sample 1,1 (line and sample 1,1 is considered the upper left corner of the digital array).  For an EQUIRECTANGULAR map projection, the value of SAMPLE_PROJECTION_OFFSET is positive for images starting to the west of the projection longitude and is negative for images starting to the east of the projection longitude.

            MAP_RESOLUTION is measured in pixels/degree.

There are four PDS parameters that specify the latitude and longitude boundaries of an image. MAXIMUM_LATITUDE and MINIMUM_LATITUDE specify the latitude boundaries of the image, and EASTERNMOST_LONGITUDE and WESTERNMOST_LONGITUDE specify the longitudinal boundaries of the map.

Definitions of other mapping parameters can be found in the PDS Data Dictionary.

Polar Stereographic Projections

For the latitude bands projected polar stereographically, projection is centered on the north or south pole. Lines of longitude extend radially from the pole and parallels of latitude are concentric circles around the center. In the north, longitude 0 extends straight down from the center and longitude 90 East extends to the right. In the south, longitude 0 extends straight up from the center, and longitude 90 East extends to the right. Thus in any given tile, north is at a variable orientation in LINE-SAMPLE space. The transformation from line and sample coordinates to planetocentric latitude and longitude is given by these equations.

            x = (SAMPLE - SAMPLE_PROJECTION_OFFSET - 0.5) * MAP_SCALE

            y = (LINE - LINE_PROJECTION_OFFSET - 0.5) * -1 * MAP_SCALE

            rho = sqrt(x^2 + y^2)

              (if rho=0, lat,lon is the reference pole)

            c = 2 * atan(rho/(2*(A_AXIS_RADIUS*1000)))

            lon = CENTER_LONGITUDE + (atan2(x,-y) * 180/pi) (northern hemisphere)

            lon = CENTER_LONGITUDE + (atan2(x,y) * 180/pi) (southern hemisphere)

            lat = 180/pi *     arcsin[cos(c)*sin(CENTER_LATITUDE*pi/180) +

              (y*sin(c)*cos(CENTER_LATITUDE*pi/180)/rho)]

where lat = latitude in degrees and lon = longitude in degrees.

            LINE_PROJECTION_OFFSET = the line offset value of the map projection origin from the line and sample 1,1 (line and sample 1,1 is considered the upper left corner of the digital array).

            SAMPLE_PROJECTION_OFFSET = the sample offset value of the map projection origin from line and sample 1,1 (line and sample 1,1 is considered the upper left corner of the digital array).

            MAP_SCALE is measured in m/pixel.

There are four PDS parameters that specify the latitude and longitude boundaries of an image.  MAXIMUM_LATITUDE and MINIMUM_LATITUDE specify the latitude boundaries of the image, and EASTERNMOST_LONGITUDE and WESTERNMOST_LONGITUDE specify the longitudinal boundaries of the map.

Definitions of other mapping parameters can be found in the PDS Data Dictionary.

 

3.3.9.4              MD3 Label Description

The detached label conforms to PDS version 3.8 standards (Applicable Document 3). The purpose of the PDS label is to describe the data product. A single label points to the IMG file. Sample MD3 labels can be found in Appendix G.  Table 3-13 below lists MDIS-specific values for MD3 label keywords.  See Appendix B for keyword descriptions.

Keyword

Valid Values

INSTRUMENT_ID

“MDIS-WAC”

PRODUCT_TYPE

MAP_PROJECTED_MD3

UNIT

“Reflectance”

BAND_NAME

Version 0 or 1:

"WAC FILTER 6 430 BP 40"

"WAC FILTER 7 750 BP 5"

"WAC FILTER 9 1000 BP 15"

Version 0:

“OBSERVATION ID”

“MDR METRIC”

"SOLAR INCIDENCE ANGLE"

"EMISSION ANGLE"

"PHASE ANGLE”

Version 1:

"IMAGE COUNT"

"STDEV WAC FILTER 6 430 BP 40"

"STDEV WAC FILTER 7 750 BP 5"

"STDEV WAC FILTER 9 1000 BP 15"

Table 3-13.  MDIS-specific values for MD3 label keywords. Reflectance is at i=30°, e=0°, g=30°.

 

3.3.10 MP5 Directory (MP5 Volumes Only)

MDIS 5-color imaging of Mercury's north polar latitudes is mosaicked into a single 128 pixel/degree tile (MP5). This tile corresponds to the pre-existing Mercury chart H01, plus the northern part of the chart to the immediate south, H02-H05.

3.3.10.1          MP5 File Naming

The file names developed for this PDS archive are restricted to a maximum 36-character base name and 3 character extension name with a period separating the file and extension names.  Also known as the “36.3” format, this is compliant with the ISO 9660 Level 2 specification (maximum of 40 characters), which is required by PDS.  The MDIS MP5 products have a “22.3” format and thus remain within the PDS specification parameters.  Below is the detailed naming convention for this dataset.

Map tiles are named based on the quadrant of the Mercury chart they span.

 

Format:  "MDIS_ppp_rrrPPD_Hxxddv.ext"

 

ppp = product type = MP5

rrr = resolution in pixels/degree (PPD)

Hxx = Mercury chart designation

dd = quadrant within Mercury chart (NW, NE, SW, or SE), or a polar chart (NP, SP)

v = version number

ext = IMG for the multiband image, LBL for the detached label

 

The following is an example file name with a description of the individual components:

 

MDIS_MP5_128PPD_H01NP1.IMG

 

For this image:

Š         Product type = MP5 (MP5)

Š         Resolution = 128 pixels/degree (128PPD)

Š         Mercury chart = Borealis (H01)

Š         Quadrant = North Polar (NP)

Š         Version = 1

 

3.3.10.2          MP5 Structure and Organization

The MP5 directory, present in the MP5 archive volume, contains the 5-color MDIS Map Projected Multispectral Reduced Data Record (MP5).  MP5 files are located in a subdirectory based on Mercury Chart.  Latitude and longitude limits of Mercury Charts and the corresponding subdirectory names are given in Table 3-10.  The center latitude and center longitude of the MP5 is located in H01 so only that directory is populated.

An MP5:

Š         Consists of a mosaic of map-projected, photometrically normalized I/F CDRs collectively forming a multispectral map tile.

Š         Contains image data in I/F corrected photometrically to i=30°, e=0°, g=30° at a resolution of 128 pixels per degree (~332 m/pixel at the equator).

Š         Represents one latitude-longitude bin in a regional color map. 

Š         Is composed of up to 5 bands corresponding to 5 of the 11 WAC filters. The 5 filters provide improved spectral sampling of color variations in the Northern Volcanic Plains geologic unit compared to the MD3 data product, and twice the spatial resolution of the MDR data product.

Š         Version 0 contains 5 backplanes for the reference 750-nm band: (a) observation id, (b) MDR metric, (c) solar incidence angle, (d) emission angle, and (e) phase angle.  “MDR metric” is a metric describing the resolution and illumination of data used to determine where and whether to overlay future imaging coverage (see section 2.5.2.3), modified for the different limiting spatial resolution.

Š         Version 1 contains 6 backplanes for the reference 750-nm band: (a) image count, and (b-f) standard deviation of the values used to determine average normalized I/F in each of the 5 bands (see section 2.5.2.3).

 

Versions increment on reprocessing or addition of new data.  The polar tile is in polar stereographic projections.

See section 2.5.2.3 for a description of how the MP5 products are generated.

 

3.3.10.3          MP5 Map Projection Standards

The projection convention adopted by the MESSENGER project is planetocentric and positive east. Prior to delivery 15, the MESSENGER team used the prime meridian and other Mercury coordinate system values described in Archinal et al. [2009, Applicable Document 12] with Mercury radii of 2440 km for products provided to PDS. For delivery 15, the MESSENGER team used the Mercury coordinate system values contained in the SPICE Planetary Constants Kernel provided to NAIF by MESSENGER with delivery 15 which included updates to the Mercury prime meridian, rotation rate, and radii (2439.4 km). The projection varies with latitude, using POLAR STEREOGRAPHIC for the MP5 product.

Polar Stereographic Projections

For the latitude bands projected polar stereographically, projection is centered on the north or south pole. Lines of longitude extend radially from the pole and parallels of latitude are concentric circles around the center. In the north, longitude 0 extends straight down from the center and longitude 90 East extends to the right. In the south, longitude 0 extends straight up from the center, and longitude 90 East extends to the right. Thus in any given tile, north is at a variable orientation in LINE-SAMPLE space. The transformation from line and sample coordinates to planetocentric latitude and longitude is given by these equations.

            x = (SAMPLE - SAMPLE_PROJECTION_OFFSET - 0.5) * MAP_SCALE

            y = (LINE - LINE_PROJECTION_OFFSET - 0.5) * -1 * MAP_SCALE

            rho = sqrt(x^2 + y^2)

              (if rho=0, lat,lon is the reference pole)

            c = 2 * atan(rho/(2*(A_AXIS_RADIUS*1000)))

            lon = CENTER_LONGITUDE + (atan2(x,-y) * 180/pi) (northern hemisphere)

            lon = CENTER_LONGITUDE + (atan2(x,y) * 180/pi) (southern hemisphere)

            lat = 180/pi *     arcsin[cos(c)*sin(CENTER_LATITUDE*pi/180) +

              (y*sin(c)*cos(CENTER_LATITUDE*pi/180)/rho)]

where lat = latitude in degrees and lon = longitude in degrees.

            LINE_PROJECTION_OFFSET = the line offset value of the map projection origin from the line and sample 1,1 (line and sample 1,1 is considered the upper left corner of the digital array).

            SAMPLE_PROJECTION_OFFSET = the sample offset value of the map projection origin from line and sample 1,1 (line and sample 1,1 is considered the upper left corner of the digital array).

            MAP_SCALE is measured in m/pixel.

There are four PDS parameters that specify the latitude and longitude boundaries of an image.  MAXIMUM_LATITUDE and MINIMUM_LATITUDE specify the latitude boundaries of the image, and EASTERNMOST_LONGITUDE and WESTERNMOST_LONGITUDE specify the longitudinal boundaries of the map.

Definitions of other mapping parameters can be found in the PDS Data Dictionary.

 

3.3.10.4          MP5 Label Description

The detached label conforms to PDS version 3.8 standards (Applicable Document 3).  The purpose of the PDS label is to describe the data product. A single label points to the IMG file. A sample MP5 label can be found in Appendix H.  Table 3-14 below lists MDIS-specific values for MP5 label keywords.  See Appendix B for keyword descriptions.

 

Keyword

Valid Values

INSTRUMENT_ID

“MDIS-WAC”

PRODUCT_TYPE

MAP_PROJECTED_MP5

UNIT

“Reflectance”

BAND_NAME

"WAC FILTER 6 430 BP 40"

"WAC FILTER 4 560 BP 5"

"WAC FILTER 7 750 BP 5"

"WAC FILTER 12 830 BP 5"

"WAC FILTER 9 1000 BP 15"

"IMAGE COUNT"

"STDEV WAC FILTER 6 430 BP 40"

"STDEV WAC FILTER 4 560 BP 5"

"STDEV WAC FILTER 7 750 BP 5"

"STDEV WAC FILTER 12 830 BP 5"

"STDEV WAC FILTER 9 1000 BP 15"

Table 3-14.  MDIS-specific values for MP5 label keywords. Reflectance is at i=30°, e=0°, g=30°.

 

3.3.11 HIE Directory (HIE Volumes Only)

MDIS near-nadir NAC and WAC 750-nm filter high incidence angle imaging of Mercury with incidence angles near 78° illuminated from the east is mosaicked into 54 non-overlapping, 256 pixel/degree tiles (HIEs). Each tile corresponds to the NW, NE, SW, or, SE quadrant of one of the pre-existing Mercury non-polar charts or one of the two polar charts. Version 0 contains only data from the high-incidence angle imaging campaign; version 1 contains data with appropriate illumination from any campaign.

3.3.11.1          HIE File Naming

The file names developed for this PDS archive are restricted to a maximum 36-character base name and 3 character extension name with a period separating the file and extension names.  Also known as the “36.3” format, this is compliant with the ISO 9660 Level 2 specification (maximum of 40 characters), which is required by PDS.  The MDIS HIE products have a “22.3” format and thus remain within the PDS specification parameters.  Below is the detailed naming convention for this dataset.

Map tiles are named based on the quadrant of the Mercury chart they span.

 

Format:  "MDIS_ppp_rrrPPD_Hxxddv.ext"

 

ppp = product type = HIE

rrr = resolution in pixels/degree (PPD)

Hxx = Mercury chart designation

dd = quadrant within Mercury chart (NW, NE, SW, or SE), or a polar chart (NP, SP)

v = version number

ext = IMG for the multiband image, LBL for the detached label

 

The following is an example file name with a description of the individual components:

 

MDIS_HIE_256PPD_H03NE0.IMG

 

For this image:

Š         Product type = HIE (HIE)

Š         Resolution = 256 pixels/degree (256PPD)

Š         Mercury chart = Shakespeare (H03)

Š         Quadrant = Northeast (NE)

Š         Version = 0

 

3.3.11.2          HIE Structure and Organization

The HIE directory, present in the HIE archive volume, contains MDIS Map Projected High Incidence Angle Basemap Illuminated from the East Reduced Data Records (HIEs).  The HIEs are organized into subdirectories based on the Mercury Chart containing the HIE.  Latitude and longitude limits of Mercury Charts and the corresponding subdirectory names are given in Table 3-10.

An HIE:

Š         Consists of an mosaic of map-projected, photometrically normalized I/F CDRs collectively forming a monochrome map tile. For version 0, only those images taken as part of the high-incidence angle campaign and having a value of SUB_SOLAR_LONGITUDE located eastward of the image CENTER_LONGITUDE (section 2.3.3.1) are included. For version 1, images from other campaigns with suitable illumination are included.

Š         Contains image data in I/F corrected photometrically to i=30°, e=0°, g=30° sampled at a scale of 256 pixels per degree (~166 meters/pixel at the equator), composed of WAC filter 7 (G) (750 BP 5) and NAC images.

Š         Represents one latitude-longitude bin in a global map. 

Š         Contains 5 backplanes: (a) observation id, (b) the BDR metric adjusted for the optimal incidence angle to be 78° instead of 74°, (c) solar incidence angle, (d) emission angle, and (e) phase angle.  “BDR metric” is a metric describing the resolution and illumination of data used to determine where and whether to overlay future imaging coverage (see section 2.5.2.3).

 

Versions increment on reprocessing or addition of new data.  Polar tiles are in polar stereographic projections, other tiles in equirectangular projection.

See section 2.5.2.3 for a description of how the HIE products are generated.

3.3.11.3          HIE Map Projection Standards 

The projection convention adopted by the MESSENGER project is planetocentric and positive east. Prior to delivery 15, the MESSENGER team used the prime meridian and other Mercury coordinate system values described in Archinal et al. [2009, Applicable Document 12] with Mercury radii of 2440 km for products provided to PDS. For delivery 15, the MESSENGER team used the Mercury coordinate system values contained in the SPICE Planetary Constants Kernel provided to NAIF by MESSENGER with delivery 15 which included updates to the Mercury prime meridian, rotation rate, and radii (2439.4 km). The projection varies with latitude, using EQUIRECTANGULAR for tiles centered equatorward of 65 degrees latitude, and POLAR STEREOGRAPHIC centered poleward of 65 degrees latitude.

Equirectangular Projections

For the latitude band projected equirectangularly, the CENTER_LATITUDE of projection is the equatorward boundary of each band to minimize 'distortion.'  The transformation from line and sample coordinates to planetocentric latitude and longitude is given by these equations.

            x = (SAMPLE - SAMPLE_PROJECTION_OFFSET - 0.5) * MAP_SCALE

            y = (LINE - LINE_PROJECTION_OFFSET - 0.5) * -1 * MAP_SCALE

            lat = y / (A_AXIS_RADIUS * 1000)

            lon = CENTER_LONGITUDE +

              180/pi * (x/(A_AXIS_RADIUS * 1000 * cos(CENTER_LATITUDE*pi/180))

Note that integral values of line and sample correspond to the center of a pixel. Lat and lon are the latitude and longitude of a given location on the surface, east positive.

            MAP_SCALE= the map scale in meters per pixel, approximately 166.3 meters/pixel for an HIE, which achieves close to the desired 256 pixels/degree at the CENTER_LATITUDE.

            LINE_PROJECTION_OFFSET = the line offset value of the map projection origin from the line and sample 1,1 (line and sample 1,1 is considered the upper left corner of the digital array). For an EQUIRECTANGULAR map projection, origin is the equatorward edge of the map tile. The value of LINE_PROJECTION_OFFSET is positive for images starting north of the equator and is negative for images starting south of the equator.

            SAMPLE_PROJECTION_OFFSET = the sample offset value of the map projection origin from line and sample 1,1 (line and sample 1,1 is considered the upper left corner of the digital array).  For an EQUIRECTANGULAR map projection, the value of SAMPLE_PROJECTION_OFFSET is positive for images starting to the west of the projection longitude and is negative for images starting to the east of the projection longitude.

            MAP_RESOLUTION is measured in pixels/degree.

There are four PDS parameters that specify the latitude and longitude boundaries of an image. MAXIMUM_LATITUDE and MINIMUM_LATITUDE specify the latitude boundaries of the image, and EASTERNMOST_LONGITUDE and WESTERNMOST_LONGITUDE specify the longitudinal boundaries of the map.

Definitions of other mapping parameters can be found in the PDS Data Dictionary.

Polar Stereographic Projections

For the latitude bands projected polar stereographically, projection is centered on the north or south pole. Lines of longitude extend radially from the pole and parallels of latitude are concentric circles around the center. In the north, longitude 0 extends straight down from the center and longitude 90 East extends to the right. In the south, longitude 0 extends straight up from the center, and longitude 90 East extends to the right. Thus in any given tile, north is at a variable orientation in LINE-SAMPLE space. The transformation from line and sample coordinates to planetocentric latitude and longitude is given by these equations.

            x = (SAMPLE - SAMPLE_PROJECTION_OFFSET - 0.5) * MAP_SCALE

            y = (LINE - LINE_PROJECTION_OFFSET - 0.5) * -1 * MAP_SCALE

            rho = sqrt(x^2 + y^2)

              (if rho=0, lat,lon is the reference pole)

            c = 2 * atan(rho/(2*(A_AXIS_RADIUS*1000)))

            lon = CENTER_LONGITUDE + (atan2(x,-y) * 180/pi) (northern hemisphere)

            lon = CENTER_LONGITUDE + (atan2(x,y) * 180/pi) (southern hemisphere)

            lat = 180/pi *     arcsin[cos(c)*sin(CENTER_LATITUDE*pi/180) +

              (y*sin(c)*cos(CENTER_LATITUDE*pi/180)/rho)]

where lat = latitude in degrees and lon = longitude in degrees.

            LINE_PROJECTION_OFFSET = the line offset value of the map projection origin from the line and sample 1,1 (line and sample 1,1 is considered the upper left corner of the digital array).

            SAMPLE_PROJECTION_OFFSET = the sample offset value of the map projection origin from line and sample 1,1 (line and sample 1,1 is considered the upper left corner of the digital array).

            MAP_SCALE is measured in m/pixel.

There are four PDS parameters that specify the latitude and longitude boundaries of an image.  MAXIMUM_LATITUDE and MINIMUM_LATITUDE specify the latitude boundaries of the image, and EASTERNMOST_LONGITUDE and WESTERNMOST_LONGITUDE specify the longitudinal boundaries of the map.

Definitions of other mapping parameters can be found in the PDS Data Dictionary.

 

3.3.11.4          HIE Label Description

The detached label conforms to PDS version 3.8 standards (Applicable Document 3).  The purpose of the PDS label is to describe the data product. A single label points to the IMG file. Sample HIE labels can be found in Appendix I.  Table 3-15 below lists MDIS-specific values for HIE label keywords.  See Appendix B for keyword descriptions.


 

Keyword

Valid Values

INSTRUMENT_ID

“MDIS-WAC”

“MDIS-NAC”

PRODUCT_TYPE

MAP_PROJECTED_HIE

UNIT

“Reflectance”

BAND_NAME

“REFLECTANCE 750NM”

“OBSERVATION ID”

“BDR METRIC”

"SOLAR INCIDENCE ANGLE"

"EMISSION ANGLE"

"PHASE ANGLE”

Table 3-15.  MDIS-specific values for HIE label keywords. Reflectance is at i=30°, e=0°, g=30°.

 

3.3.12 HIW Directory (HIW Volumes Only)

MDIS near-nadir NAC and WAC 750-nm high incidence angle imaging of Mercury with incidence angles near 78° illuminated from the west is mosaicked into 54 non-overlapping, 256 pixel/degree tiles (HIWs). Each tile corresponds to the NW, NE, SW, or, SE quadrant of one of the pre-existing Mercury non-polar charts or one of the two polar charts. Version 0 contains only data from the high-incidence angle imaging campaign; version 1 contains data with appropriate illumination from any campaign.

3.3.12.1          HIW File Naming

The file names developed for this PDS archive are restricted to a maximum 36-character base name and 3 character extension name with a period separating the file and extension names.  Also known as the “36.3” format, this is compliant with the ISO 9660 Level 2 specification (maximum of 40 characters), which is required by PDS.  The MDIS HIW products have a “22.3” format and thus remain within the PDS specification parameters.  Below is the detailed naming convention for this dataset.

Map tiles are named based on the quadrant of the Mercury chart they span.

 

Format:  "MDIS_ppp_rrrPPD_Hxxddv.ext"

 

ppp = product type = HIW

rrr = resolution in pixels/degree (PPD)

Hxx = Mercury chart designation

dd = quadrant within Mercury chart (NW, NE, SW, or SE), or a polar chart (NP, SP)

v = version number

ext = IMG for the multiband image, LBL for the detached label

 

The following is an example file name with a description of the individual components:

 

MDIS_HIW_256PPD_H03NE0.IMG

 

For this image:

Š         Product type = HIW (HIW)

Š         Resolution = 256 pixels/degree (256PPD)

Š         Mercury chart = Shakespeare (H03)

Š         Quadrant = Northeast (NE)

Š         Version = 0

Š         Is accompanied by a label and possibly by an ENVI header.

 

3.3.12.2          HIW Structure and Organization

The HIW directory, present in the HIW archive volume, contains MDIS Map Projected High Incidence Angle Basemap Illuminated from the West Reduced Data Records (HIWs).  The HIWs are organized into subdirectories based on the Mercury Chart containing the HIW.  Latitude and longitude limits of Mercury Charts and the corresponding subdirectory names are given in Table 3-10.

An HIW:

Š         Consists of an uncontrolled mosaic of map-projected, photometrically normalized I/F CDRs collectively forming a monochrome map tile. For version 0, only those images taken as part of the high-incidence angle campaign and having a value of SUB_SOLAR_LONGITUDE located westward of the image CENTER_LONGITUDE (section 2.3.3.1) are included. For version 1, images from other campaigns with suitable illumination are included.

Š         Contains image data in I/F corrected photometrically to i=30°, e=0°, g=30° sampled at a scale of 256 pixels per degree (~166 meters/pixel at the equator), composed of WAC filter 7 (G) (750 BP 5) and NAC images.

Š         Represents one latitude-longitude bin in a global map. 

Š         Contains 5 backplanes: (a) observation id, (b) the BDR metric adjusted for the optimal incidence angle to be 78° instead of 74°, (c) solar incidence angle, (d) emission angle, and (e) phase angle.  “BDR metric” is a metric describing the resolution and illumination of data used to determine where and whether to overlay future imaging coverage (see section 2.5.2.3).

 

Versions increment on reprocessing or addition of new data.  Polar tiles are in polar stereographic projections, other tiles in equirectangular projection.

See section 2.5.2.3 for a description of how the HIW products are generated.

3.3.12.3          HIW Map Projection Standards 

The projection convention adopted by the MESSENGER project is planetocentric and positive east. Prior to delivery 15, the MESSENGER team used the prime meridian and other Mercury coordinate system values described in Archinal et al. [2009, Applicable Document 12] with Mercury radii of 2440 km for products provided to PDS. For delivery 15, the MESSENGER team used the Mercury coordinate system values contained in the SPICE Planetary Constants Kernel provided to NAIF by MESSENGER with delivery 15 which included updates to the Mercury prime meridian, rotation rate, and radii (2439.4 km). The projection varies with latitude, using EQUIRECTANGULAR for tiles centered equatorward of 65 degrees latitude, and POLAR STEREOGRAPHIC centered poleward of 65 degrees latitude.

Equirectangular Projections

For the latitude band projected equirectangularly, the CENTER_LATITUDE of projection is the equatorward boundary of each band to minimize 'distortion.'  The transformation from line and sample coordinates to planetocentric latitude and longitude is given by these equations.

            x = (SAMPLE - SAMPLE_PROJECTION_OFFSET - 0.5) * MAP_SCALE

            y = (LINE - LINE_PROJECTION_OFFSET - 0.5) * -1 * MAP_SCALE

            lat = y / (A_AXIS_RADIUS * 1000)

            lon = CENTER_LONGITUDE +

              180/pi * (x/(A_AXIS_RADIUS * 1000 * cos(CENTER_LATITUDE*pi/180))

Note that integral values of line and sample correspond to the center of a pixel. Lat and lon are the latitude and longitude of a given location on the surface, east positive.

            MAP_SCALE= the map scale in meters per pixel, approximately 166.3 meters/pixel for an HIW, which achieves close to the desired 256 pixels/degree at the CENTER_LATITUDE.

            LINE_PROJECTION_OFFSET = the line offset value of the map projection origin from the line and sample 1,1 (line and sample 1,1 is considered the upper left corner of the digital array). For an EQUIRECTANGULAR map projection, origin is the equatorward edge of the map tile. The value of LINE_PROJECTION_OFFSET is positive for images starting north of the equator and is negative for images starting south of the equator.

            SAMPLE_PROJECTION_OFFSET = the sample offset value of the map projection origin from line and sample 1,1 (line and sample 1,1 is considered the upper left corner of the digital array).  For an EQUIRECTANGULAR map projection, the value of SAMPLE_PROJECTION_OFFSET is positive for images starting to the west of the projection longitude and is negative for images starting to the east of the projection longitude.

            MAP_RESOLUTION is measured in pixels/degree.

There are four PDS parameters that specify the latitude and longitude boundaries of an image. MAXIMUM_LATITUDE and MINIMUM_LATITUDE specify the latitude boundaries of the image, and EASTERNMOST_LONGITUDE and WESTERNMOST_LONGITUDE specify the longitudinal boundaries of the map.

Definitions of other mapping parameters can be found in the PDS Data Dictionary.

Polar Stereographic Projections

For the latitude bands projected polar stereographically, projection is centered on the north or south pole. Lines of longitude extend radially from the pole and parallels of latitude are concentric circles around the center. In the north, longitude 0 extends straight down from the center and longitude 90 East extends to the right. In the south, longitude 0 extends straight up from the center, and longitude 90 East extends to the right. Thus in any given tile, north is at a variable orientation in LINE-SAMPLE space. The transformation from line and sample coordinates to planetocentric latitude and longitude is given by these equations.

            x = (SAMPLE - SAMPLE_PROJECTION_OFFSET - 0.5) * MAP_SCALE

            y = (LINE - LINE_PROJECTION_OFFSET - 0.5) * -1 * MAP_SCALE

            rho = sqrt(x^2 + y^2)

              (if rho=0, lat,lon is the reference pole)

            c = 2 * atan(rho/(2*(A_AXIS_RADIUS*1000)))

            lon = CENTER_LONGITUDE + (atan2(x,-y) * 180/pi) (northern hemisphere)

            lon = CENTER_LONGITUDE + (atan2(x,y) * 180/pi) (southern hemisphere)

            lat = 180/pi *     arcsin[cos(c)*sin(CENTER_LATITUDE*pi/180) +

              (y*sin(c)*cos(CENTER_LATITUDE*pi/180)/rho)]

where lat = latitude in degrees and lon = longitude in degrees.

            LINE_PROJECTION_OFFSET = the line offset value of the map projection origin from the line and sample 1,1 (line and sample 1,1 is considered the upper left corner of the digital array).

            SAMPLE_PROJECTION_OFFSET = the sample offset value of the map projection origin from line and sample 1,1 (line and sample 1,1 is considered the upper left corner of the digital array).

            MAP_SCALE is measured in m/pixel.

There are four PDS parameters that specify the latitude and longitude boundaries of an image.  MAXIMUM_LATITUDE and MINIMUM_LATITUDE specify the latitude boundaries of the image, and EASTERNMOST_LONGITUDE and WESTERNMOST_LONGITUDE specify the longitudinal boundaries of the map.

Definitions of other mapping parameters can be found in the PDS Data Dictionary.

 

3.3.12.4          HIW Label Description

The detached label conforms to PDS version 3.8 standards (Applicable Document 3).  The purpose of the PDS label is to describe the data product. A single label points to the IMG file. Sample HIW labels can be found in Appendix J.  Table 3-16 below lists MDIS-specific values for HIW label keywords.  See Appendix B for keyword descriptions.

Keyword

Valid Values

INSTRUMENT_ID

“MDIS-WAC”

“MDIS-NAC”

PRODUCT_TYPE

MAP_PROJECTED_HIW

UNIT

“Reflectance”

BAND_NAME

“REFLECTANCE 750NM”

“OBSERVATION ID”

“BDR METRIC”

"SOLAR INCIDENCE ANGLE"

"EMISSION ANGLE"

"PHASE ANGLE”

Table 3-16.  MDIS-specific values for HIW label keywords. Reflectance is at i=30°, e=0°, g=30°.

 

3.3.13 LOI Directory (LOI Volumes Only)

MDIS near-nadir NAC and WAC 750-nm filter low incidence angle imaging of Mercury with incidence angles near 45° is mosaicked into 54 non-overlapping, 256 pixel/degree tiles (LOIs). Each tile corresponds to the NW, NE, SW, or, SE quadrant of one of the pre-existing Mercury non-polar charts or one of the two polar charts. Version 0 contains only data from the low-incidence angle albedo campaign; version 1 contains data with appropriate illumination from any campaign.

3.3.13.1          LOI File Naming

The file names developed for this PDS archive are restricted to a maximum 36-character base name and 3 character extension name with a period separating the file and extension names.  Also known as the “36.3” format, this is compliant with the ISO 9660 Level 2 specification (maximum of 40 characters), which is required by PDS.  The MDIS LOI products have a “22.3” format and thus remain within the PDS specification parameters.  Below is the detailed naming convention for this dataset.

Map tiles are named based on the quadrant of the Mercury chart they span.

 

Format:  "MDIS_ppp_rrrPPD_Hxxddv.ext"

 

ppp = product type = LOI

rrr = resolution in pixels/degree (PPD)

Hxx = Mercury chart designation

dd = quadrant within Mercury chart (NW, NE, SW, or SE), or a polar chart (NP, SP)

v = version number

ext = IMG for the multiband image, LBL for the detached label

 

The following is an example file name with a description of the individual components:

 

MDIS_LOI_256PPD_H03NE1.IMG

 

For this image:

Š         Product type = LOI (LOI)

Š         Resolution = 256 pixels/degree (256PPD)

Š         Mercury chart = Shakespeare (H03)

Š         Quadrant = Northeast (NE)

Š         Version = 1

 

3.3.13.2          LOI Structure and Organization

The LOI directory, present in the LOI archive volume, contains MDIS Map Projected Low Incidence Angle Basemap Reduced Data Records (LOIs).  The LOIs are organized into subdirectories based on the Mercury Chart containing the LOI.  Latitude and longitude limits of Mercury Charts and the corresponding subdirectory names are given in Table 3-10.

An LOI:

Š         Consists of an uncontrolled mosaic of map-projected, photometrically normalized I/F CDRs collectively forming a monochrome map tile. For version 0, only those images taken as part of the near-nadir part of the low-incidence angle campaign are included. For version 1, images from other campaigns with suitable illumination are included.

Š         Contains image data in I/F corrected photometrically to i=30°, e=0°, g=30° sampled at a scale of 256 pixels per degree (~166 meters/pixel at the equator), composed of WAC filter 7 (G) (750 BP 5) and NAC images.

Š         Represents one latitude-longitude bin in a global map. 

Š         Contains 5 backplanes: (a) observation id, (b) the MDR metric adjusted for the different limiting resolution, (c) solar incidence angle, (d) emission angle, and (e) phase angle.  “MDR metric” is a metric describing the resolution and illumination of data used, to determine where and whether to overlay future imaging coverage (see section 2.5.2.3).

 

Versions increment on reprocessing or addition of new data.  Polar tiles are in polar stereographic projections, other tiles in equirectangular projection.

See section 2.5.2.3 for a description of how the LOI products are generated.

3.3.13.3          LOI Map Projection Standards 

The projection convention adopted by the MESSENGER project is planetocentric and positive east. Prior to delivery 15, the MESSENGER team used the prime meridian and other Mercury coordinate system values described in Archinal et al. [2009, Applicable Document 12] with Mercury radii of 2440 km for products provided to PDS. For delivery 15, the MESSENGER team used the Mercury coordinate system values contained in the SPICE Planetary Constants Kernel provided to NAIF by MESSENGER with delivery 15 which included updates to the Mercury prime meridian, rotation rate, and radii (2439.4 km). The projection varies with latitude, using EQUIRECTANGULAR for tiles centered equatorward of 65 degrees latitude, and POLAR STEREOGRAPHIC centered poleward of 65 degrees latitude.

Equirectangular Projections

For the latitude band projected equirectangularly, the CENTER_LATITUDE of projection is the equatorward boundary of each band to minimize 'distortion.'  The transformation from line and sample coordinates to planetocentric latitude and longitude is given by these equations.

            x = (SAMPLE - SAMPLE_PROJECTION_OFFSET - 0.5) * MAP_SCALE

            y = (LINE - LINE_PROJECTION_OFFSET - 0.5) * -1 * MAP_SCALE

            lat = y / (A_AXIS_RADIUS * 1000)

            lon = CENTER_LONGITUDE +

              180/pi * (x/(A_AXIS_RADIUS * 1000 * cos(CENTER_LATITUDE*pi/180))

Note that integral values of line and sample correspond to the center of a pixel. Lat and lon are the latitude and longitude of a given location on the surface, east positive.

            MAP_SCALE= the map scale in meters per pixel, approximately166.3 meters/pixel for an LOI, which achieves close to the desired 256 pixels/degree at the CENTER_LATITUDE.

            LINE_PROJECTION_OFFSET = the line offset value of the map projection origin from the line and sample 1,1 (line and sample 1,1 is considered the upper left corner of the digital array). For an EQUIRECTANGULAR map projection, origin is the equatorward edge of the map tile. The value of LINE_PROJECTION_OFFSET is positive for images starting north of the equator and is negative for images starting south of the equator.

            SAMPLE_PROJECTION_OFFSET = the sample offset value of the map projection origin from line and sample 1,1 (line and sample 1,1 is considered the upper left corner of the digital array).  For an EQUIRECTANGULAR map projection, the value of SAMPLE_PROJECTION_OFFSET is positive for images starting to the west of the projection longitude and is negative for images starting to the east of the projection longitude.

            MAP_RESOLUTION is measured in pixels/degree.

There are four PDS parameters that specify the latitude and longitude boundaries of an image. MAXIMUM_LATITUDE and MINIMUM_LATITUDE specify the latitude boundaries of the image, and EASTERNMOST_LONGITUDE and WESTERNMOST_LONGITUDE specify the longitudinal boundaries of the map.

Definitions of other mapping parameters can be found in the PDS Data Dictionary.

Polar Stereographic Projections

For the latitude bands projected polar stereographically, projection is centered on the north or south pole. Lines of longitude extend radially from the pole and parallels of latitude are concentric circles around the center. In the north, longitude 0 extends straight down from the center and longitude 90 East extends to the right. In the south, longitude 0 extends straight up from the center, and longitude 90 East extends to the right. Thus in any given tile, north is at a variable orientation in LINE-SAMPLE space. The transformation from line and sample coordinates to planetocentric latitude and longitude is given by these equations.

            x = (SAMPLE - SAMPLE_PROJECTION_OFFSET - 0.5) * MAP_SCALE

            y = (LINE - LINE_PROJECTION_OFFSET - 0.5) * -1 * MAP_SCALE

            rho = sqrt(x^2 + y^2)

              (if rho=0, lat,lon is the reference pole)

            c = 2 * atan(rho/(2*(A_AXIS_RADIUS*1000)))

            lon = CENTER_LONGITUDE + (atan2(x,-y) * 180/pi) (northern hemisphere)

            lon = CENTER_LONGITUDE + (atan2(x,y) * 180/pi) (southern hemisphere)

            lat = 180/pi *     arcsin[cos(c)*sin(CENTER_LATITUDE*pi/180) +

              (y*sin(c)*cos(CENTER_LATITUDE*pi/180)/rho)]

where lat = latitude in degrees and lon = longitude in degrees.

            LINE_PROJECTION_OFFSET = the line offset value of the map projection origin from the line and sample 1,1 (line and sample 1,1 is considered the upper left corner of the digital array).

            SAMPLE_PROJECTION_OFFSET = the sample offset value of the map projection origin from line and sample 1,1 (line and sample 1,1 is considered the upper left corner of the digital array).

            MAP_SCALE is measured in m/pixel.

There are four PDS parameters that specify the latitude and longitude boundaries of an image.  MAXIMUM_LATITUDE and MINIMUM_LATITUDE specify the latitude boundaries of the image, and EASTERNMOST_LONGITUDE and WESTERNMOST_LONGITUDE specify the longitudinal boundaries of the map.

Definitions of other mapping parameters can be found in the PDS Data Dictionary.

 

3.3.13.4          LOI Label Description

The detached label conforms to PDS version 3.8 standards (Applicable Document 3).  The purpose of the PDS label is to describe the data product. A single label points to the IMG file. Sample LOI labels can be found in Appendix K.  Table 3-17 below lists MDIS-specific values for LOI label keywords.  See Appendix B for keyword descriptions.

Keyword

Valid Values

INSTRUMENT_ID

“MDIS-WAC”

“MDIS-NAC”

PRODUCT_TYPE

MAP_PROJECTED_LOI

UNIT

“Reflectance”

BAND_NAME

“REFLECTANCE 750NM”

“OBSERVATION ID”

“MDR METRIC”

"SOLAR INCIDENCE ANGLE"

"EMISSION ANGLE"

"PHASE ANGLE”

Table 3-17.  MDIS-specific values for LOI label keywords. Reflectance is at i=30°, e=0°, g=30°.

 

3.3.14 RTM Directory (RTM Volumes Only)

Key types of MDIS targeted observations are mosaicked into Regional Targeted Mosaics (RTMs). Unlike the global and regional mapping campaign map products, which are divided into a regular pattern of tiles based on Mercury Charts, each RTM is based on one MESSENGER Science Team-Defined "region of interest" that is the target of the images. That region of interest is encoded in the keyword SITE_ID and also appears in the PRODUCT_ID. It is referenced in a list of site IDs explaining the science motivation for their targeting, found in the EXTRAS directory.

3.3.14.1          RTM File Naming

The file names developed for this PDS archive are restricted to a maximum 36-character base name and 3 character extension name with a period separating the file and extension names.  Also known as the “36.3” format, this is compliant with the ISO 9660 Level 2 specification (maximum of 40 characters), which is required by PDS.  The MDIS RTM products have a “29.3” format and thus remain within the PDS specification parameters.  Below is the detailed naming convention for this dataset.

RTM products are named based on their SITE_ID, OBSERVATION_ID, and image contents they contain.

 

Format:  "MDIS_ppp_cbb_siteid_observationid_v.ext"

 

ppp = product type = RTM

c = camera (W WAC or N NAC)

bb = bands (01, 03, 08, 11 depending on type of observation)

siteid = a 6-digit integer giving the unique SITE_ID of the region covered by the product

observationid = image observation ID of the first image (lowest ID)

v = version number

ext = IMG for the multiband image, LBL for the detached label

 

The following is an example file name with a description of the individual components:

 

MDIS_RTM_N01_000276_1214047_1.IMG

 

For this image:

Š         Product type = RTM (RTM)

Š         Camera = NAC (N)

Š         Bands = 1 (01)

Š         SITE_ID = 276 (000276)

Š         OBSERVATION_ID = 1214047

Š         Version = 1

 

3.3.14.2          RTM Structure and Organization

The RTM directory, present in the RTM archive volume, contains MDIS Map Projected Regional Targeted Mosaics (RTMs).  The RTMs are organized into subdirectories based on the camera/band (cbb from filename) and then within those subdirectories, by year and day of year on which the images were acquired, referencing the start image.  The structure is generalized to allow for the fact that some targeted observations were taken with the NAC and some with the WAC, and that the number of WAC bands depends on the purpose of the observation (see sections 2.3.1.5, 2.3.1.6, 2.3.1.7, and 2.3.3.5).         

An RTM:

Š         Consists of an mosaic of map-projected, photometrically normalized I/F CDRs. Only those images taken as part of coverage of a specific SITE_ID are included.

Š         Contains image data in I/F corrected photometrically to i=30°, e=0°, g=30° sampled at variable pixel scale depending on the observation.

Š         May contain 3 to 11 bands of WAC images or 1 band with one or more NAC images.

Š         Is a self-contained product and not part of a larger global map. 

Š         NAC mosaics contain 4 backplanes: (a) observation id, (b) solar incidence angle, (c) emission angle, and (d) phase angle. 

Š         WAC color products contain 3 backplanes:  (a) solar incidence angle, (b) emission angle, and (c) phase angle. 

 

Versions increment on reprocessing.  All products are in orthographic projection.

See section 2.5.2.3 for a description of how the RTM products are generated.

3.3.14.3          RTM Map Projection Standards 

The projection convention adopted by the MESSENGER project is planetocentric and positive east. Prior to delivery 15, the MESSENGER team used the prime meridian and other Mercury coordinate system values described in Archinal et al. [2009, Applicable Document 12] with Mercury radii of 2440 km for products provided to PDS. For delivery 15, the MESSENGER team used the Mercury coordinate system values contained in the SPICE Planetary Constants Kernel provided to NAIF by MESSENGER with delivery 15 which included updates to the Mercury prime meridian, rotation rate, and radii (2439.4 km). The projection varies with latitude, using ORTHOGRAPHIC for all RTM products.

The CENTER_LATITUDE and CENTER_LONGITUDE are at the origin of the Orthographic projection.   CENTER_LATITUDE is also the latitude of the central point of the Orthographic projection.

The transformation from line and sample coordinates to planetocentric latitude and longitude is given by these equations.

            x = (SAMPLE - SAMPLE_PROJECTION_OFFSET - 0.5) * MAP_SCALE

            y = (LINE - LINE_PROJECTION_OFFSET - 0.5) * -1 * MAP_SCALE

            rho = sqrt(x^2 + y^2)

               (if rho=0, lat,lon is CENTER_LATITUDE,CENTER_LONGITUDE)

            c = arcsin[rho/(A_AXIS_RADIUS * 1000)]

            clatr = CENTER_LATITUDE * pi/180

            lat = arcsin[cos(c) * sin(clatr) + (y * sin(c) * cos(clatr)/rho)]

            lon = CENTER_LONGITUDE +

            arctan[x*sin(c)/(rho*cos(clatr)*cos(c) - y*sin(clatr)*sin(c))]

where lat = latitude and lon = longitude, east positive.

            LINE_PROJECTION_OFFSET = the line offset value of the map projection origin from the line and sample 1,1 (line and sample 1,1 is considered the upper left corner of the digital array). This is equivalent to the line number of at the center of the map minus the line number in the upper left corner.

            SAMPLE_PROJECTION_OFFSET = the sample offset value of the map projection origin from line and sample 1,1 (line and sample 1,1 is considered the upper left corner of the digital array). This is equivalent to the sample number of at the center of the map minus the sample number in the upper left corner.

            MAP_SCALE is measured in m/pixel.

There are four PDS parameters that specify the latitude and longitude boundaries of an image.  MAXIMUM_LATITUDE and MINIMUM_LATITUDE specify the latitude boundaries of the image, and EASTERNMOST_LONGITUDE and WESTERNMOST_LONGITUDE specify the longitudinal boundaries of the map.

Definitions of other mapping parameters can be found in the PDS Data Dictionary.

 

3.3.14.4          RTM Label Description

The detached label conforms to PDS version 3.8 standards (Applicable Document 3).  The purpose of the PDS label is to describe the data product. A single label points to the IMG file. Sample RTM labels can be found in Appendix L.  Table 3-18 below lists MDIS-specific values for RTM label keywords.  See Appendix B for keyword descriptions.

 

Keyword

Valid Values

INSTRUMENT_ID

“MDIS-WAC”

“MDIS-NAC”

PRODUCT_TYPE

MAP_PROJECTED_RTM

UNIT

“Reflectance”

BAND_NAME

"WAC FILTER 6 430 BP 40"

"WAC FILTER 3 480 BP 10"

"WAC FILTER 4 560 BP 5"

"WAC FILTER 5 630 BP 5"

"WAC FILTER 1 700 BP 5"

"WAC FILTER 7 750 BP 5"

"WAC FILTER 12 830 BP 5"

"WAC FILTER 10 900 BP 5"

"WAC FILTER 8 950 BP 7"

"WAC FILTER 9 1000 BP 15"

"WAC FILTER 11 1020 BP 40"

“REFLECTANCE 750NM”

“OBSERVATION ID”

"SOLAR INCIDENCE ANGLE"

"EMISSION ANGLE"

"PHASE ANGLE”

Table 3-18.  MDIS-specific values for RTM label keywords. Reflectance is at i=30°, e=0°, g=30°.

 

3.3.15 Calib Directory

The Calib directory (Table 3-19) contains the calibration files used in the processing of the raw data to create the CDRs or needed to use the data products on the volume.  The EDR and CDR volumes contain all of the files listed in the table. The MD3, MDR, MP5, and RTM volumes contain only bandpass filters of NAC or WAC bands present in the data, that may be useful for analysis of the respective data. 

 

File Name

Req.?

File Contents

CALINFO.TXT

Yes

Describes the contents of this directory.

LUT_INVERT/

No

This directory contains the inverse lookup table required for inverting 8-bit images into their original 12-bit format.

 

MDISLUTINV_0.TAB

No

This file contains 8-bit values, and the 12-bit values to which they correspond. There is one set of 12-bit values for each of the eight available lookup tables in the instrument.

MDISLUTINV_0.LBL

No

The label that describes the preceding file.

 

DARK_MODEL/

No

This directory contains tables of coefficients needed to model the dark level in the NAC or WAC, with on-chip pixel binning turned on or not.

 

MDIScam_bining_DARKMODEL_v.TAB

No

cam = camera, NAC or WAC

bining = binning, NOTBIN or BINNED

v = version number, 0-9, a-z

MDIScam_bining_DARKMODEL_v.LBL

No

Detached labels describing the tables.

FLAT/

No

This directory contains flat-field images which correct for response variations from pixel to pixel and across the CCD. There are separate files for each of the 12 WAC filters and for the NAC, with on-chip pixel binning turned on or not.

 

MDISWAC_bining_FLAT_FILT_nn_v.FIT

No

bining = binning, NOTBIN or BINNED

nn = filter number, 1-12

v = version number, 0-9, a-z

MDISWAC_bining_FLAT_FILT_nn_v.LBL

No

Detached labels describing the WAC flat-field images.

MDISNAC_bining_FLAT_v.FIT

No

bining = binning, NOTBIN or BINNED

v = version number, 0-9, a-z

MDISNAC_bining_FLAT_v.LBL

No

Detached labels describing the NAC flat-field images.

RESPONSIVITY/

No

This directory contains tables of coefficients used to convert corrected DN to units of radiance. There are separate tables for the WAC and NAC, with on-chip pixel binning turned on or not.

 

MDIScam_bining_RESP_v.TAB

No

cam = camera, NAC or WAC

bining = binning, NOTBIN or BINNED

v = version number, 0-9, a-z

MDIScam_bining_RESP_v.LBL

No

Detached labels describing the tables.

CORRECT/

No

This directory contains tables of coefficients used to correct the radiance conversion for effects of contamination of WAC optics. There is one table for the WAC.

 

MDISWAC_CORRECT_v.TAB

No

v = version number, 0-9, a-z

MDISWAC_CORRECT_v.LBL

No

Detached labels describing the tables.

SOLAR/

No

This directory contains tables of solar irradiance used to convert radiance to units of I/F. There are separate tables for the WAC and NAC.

 

MDIScam_SOLAR_v.TAB

No

cam = camera, NAC or WAC

v = version number, 0-9, a-z

MDIScam_SOLAR_v.LBL

No

Detached labels describing the tables.

SUPPORT/

No

This directory contains characterizations of the instrument that are not part of the calibration process per se, but were used to derive the calibration files that are used.

 

MDISLUTFWD_0.TAB

No

Contains the onboard forward lookup tables used optionally to convert 12-bit to 8-bit images.

MDISLUTFWD_0.LBL

No

The label that describes the preceding file.

 

MDISBPcf.TAB

No

Tables giving bandpasses for each WAC filter and for the NAC.

c = N for NAC, W for WAC

f = A through M for different filters

For the NAC, f = M

For the WAC, f =

  A for Filter 1, 700 BP 5;

  B for Filter 2, 700 BP 600;

  C for Filter 3, 480 BP 10;

  D for Filter 4, 560 BP 5;

  E for Filter 5, 630 BP 5;

  F for Filter 6, 430 BP 40;

  G for Filter 7, 750 BP 5;

  H for Filter 8, 950 BP 7;

  I for Filter 9, 1000 BP 15;

  J for Filter 10, 900 BP 5;

  K for Filter 11, 1020 BP 40;

  L for Filter 12, 830 BP 5

MDISBPWa.LBL

No

The label that describes the preceding file.

 

Table 3-19:  Calib Directory Contents.

3.3.16 Geometry Directory

The GEOMETRY directory, included on the EDR and CDR volumes only, contains the file GEOMINFO.TXT that points to and describes the function of each SPICE kernel relevant to MDIS.

3.3.17 Browse Directory

If it is populated, the BROWSE directory contains synoptic versions of data products to help identify products of interest.  Each set of browse products is organized into a separate subdirectory within the BDR, MDR, MD3, MP5, HIE, HIW, LOI, and RTM archives. At the top of the directory structure, BROWINFO.TXT contains a description of the contents of this directory. Within each BROWSE directory the organization of subdirectories parallels that of the directories containing the data products (e.g., BDR, MDR, etc.). All browse products have the same line and sample dimensions, pixel scale, and map projection as the parent data products.

Browse products nomenclature follows that of the parent data product, with the unique product ID appended with the string "_BR". For example, for the BDR file whose product ID is

MDIS_BDR_256PPD_H03NE0

the product ID for the corresponding browse product is

MDIS_BDR_256PPD_H03NE0_BR

Browse products may be generated in either or both of two formats, each scaled from I/F in the parent IMG file, a Portable Network Graphics (PNG) format and a Geographic Tagged Image File Format (GeoTIFF).

3.3.17.1          Browse Products for BDR, HIE, HIW, and LOI Files

BDR, HIE, HIW, and LOI browse products are single-band gray-scale images whose parent data are a mix of NAC images and WAC 750-nm images. A different uniform, global stretch of reflectance at i=30°, e=0°, g=30° to an 8-bit integer is applied to each product type.

3.3.17.2          Browse Products for MDR, MD3, and MP5 Files

MDR, MD3, and MP5 browse products are 3-band RGB images, each constructed using data from WAC filters 9, 7, and 6 (1000, 750, and 430 nm) in the red, green and blue image planes. All three of these filters are present in all three of the data product types. A uniform, global stretch of reflectance at i=30°, e=0°, g=30° to an 8-bit integer is applied to all product types.

3.3.17.3          Browse Products for RTM Files

RTM browse products come in two types. Those constructed from 3-, 8-, or 11-color WAC targeted observations are 3-band RGB images, constructed using data from WAC filters 9, 7, and 6 (1000, 750, and 430 nm) in the red, green and blue image planes. A local stretch of reflectance at i=30°, e=0°, g=30° to an 8-bit integer specific is applied to the individual RTM product. Those constructed from NAC images are single-band gray-scale images. A local stretch of reflectance to an 8-bit integer specific is applied to the individual RTM product.

3.3.18 Extras Directory

The extras directory in the BDR, HIE, HIW, LOI, MDR, MD3, MP5, and RTM archives contain shapefiles that record for any appropriate MDIS image its coverage of Mercury during the orbital mission.  In addition to the spatial coverage info, each record has attributes describing the image that are extracted from the PDS labels.

The BDR, HIE, HIW, LOI, and RTM volumes contain a subdirectory img_footprints/cumulative that includes all images covering part of Mercury that were acquired during the orbital mission. The BDR, HIE, HIW, and LOI volumes contain a subdirectory img_footprints/controlled_only that covers the subset of images that are in the USGS global control set.

The following image polygon attributes are contained in the shapefiles in the above directories:

Š         obs_id[INT] -- image observation ID

Š         filename -- image filename

Š         ydoy_path -- Year, Day of Year storage path.  i.e. (2015_001)

Š         obs_type -- text description of intent of image

Š         site_id -- for targeted images, the ID of the site of interest

Š         instr_id -- imager, MDIS-NAC or MDIS-WAC

Š         dqi -- data quality ID, see Data Product SIS for description

Š         phase_name -- Name of mission phase.  i.e. "MERCURY ORBIT YEAR 4"

Š         start_time -- Image exposure start time

Š         seq_name -- Unused for MESSENGER Mercury orbit phases

Š         sc_alt[FLOAT] -- spacecraft altitude

Š         met_exp[FLOAT] -- MET assigned to exposure (not the exposure start)

Š         det_temp[FLOAT] -- Detector temperature in degC

Š         exp_drtn[FLOAT] -- exposure duration in milliseconds

Š         filter_no[INT] -- filter number (1-12 for WAC, 0 for NAC)

Š         lines[INT] -- number of lines

Š         samples[INT] -- number of columns

Š         sat_pix[INT] -- number of saturated pixels

Š         center_lat[FLOAT] -- latitude of image center in degrees

Š         center_lon[FLOAT] -- longitude of image center in degrees

Š         slant_d[FLOAT] -- distance from camera to intercept of image center in km

Š         smear_mag[FLOAT] -- smear magnitude in pixels

Š         i_angle[FLOAT] -- solar incidence angle of image center in degrees

Š         p_angle[FLOAT] -- solar phase angle of image center in degrees

Š         e_angle[FLOAT] -- emission angle of image center in degrees

Š         hor_scale[FLOAT] -- horizontal pixel scale of image center in meters

Š         ver_scale[FLOAT] -- vertical pixel scale of image center in meters

For images that are candidates for inclusion in global map products, the following quality scores used for stacking images into a map (lower is better) are also included. These are based on combinations of image resolution, incidence and emission angles:

Š         bdr_metric[FLOAT] -- monochrome map (68deg incidence)

Š         bdr_met2[FLOAT] -- alternate formula monochrome map

Š         mdr_metric[FLOAT] -- 8-color map

Š         hsi_metric[FLOAT] -- high-incidence map

Š         alb_metric[FLOAT] -- albedo, or low-incidence map

Š         md3_metric[FLOAT] -- 3-color map

Š         bdr_i71met[FLOAT] -- alternate for monochrome map (71deg incidence)

Š         bdr_i74met[FLOAT] -- alternate for monochrome map (74deg incidence)

Š         bdr_i77met[FLOAT] -- alternate for monochrome map (77deg incidence)

The following information is also included, which captures instrument set-up at the time of data acquisition and other measures of image geometry:

Š         piv_goal[FLOAT] -- goal angle for pivot platform in counts (when applicable)

Š         piv_pos[FLOAT] -- pivot angle for pivot platform in counts

Š         piv_read[FLOAT] -- pivot resolver angle in counts

Š         comp12_8[FLOAT] -- 12 to 8 bit compression flag

Š         comp_alg[FLOAT] -- 8 bit lookup table number used for compression

Š         smear_az[FLOAT] -- smear azimuth in degrees

Š         north_az[FLOAT] -- north azimuth in degrees

Š         sub_sc_az[FLOAT] -- sub-spacecraft point aziumuth in degrees

Š         sub_sol_az[FLOAT] -- sub-solar point azimuth in degrees

Š         wvl_ratio[INT] -- wavelet compression ratio

Š         sub_sc_lat[FLOAT] -- sub-spacecraft point latitude in degrees

Š         sub_sc_lon[FLOAT] -- sub-spacecraft point longitude in degrees

Š         subsol_lat[FLOAT] -- sub-solar point latitude in degrees

Š         subsol_lon[FLOAT] -- sub-solar point longitude in degrees

Š         subsol_ga[FLOAT] -- sub-solar ground azimuth computed using sub-solar azimuth and north azimuth

Š         subsol_ga2[FLOAT] -- sub-solar ground azimuth computed using image center lat/lon and sub-solar lat/lon

Archives that include global or regional color map products (MDR, MD3, MP5 volumes) contain a subdirectory with shapefiles that describe the areas of overlapping coverage within individual sets of 3, 5, or 8 filters. The subdirectory clr_footprints/mdr contains shapefiles for the 8-color global campaign contained in the MDR archive; clr_footprints/md3 contains shapefiles for the 3-color global campaign contained in the MD3 archive; clr_footprints/md3/H01 contains shapefiles for the 3-color campaign color set used for north polar map tile H01 in the MD3 archive; and clr_footprints/mp5 contains shapefiles for the minimized phase angle 5-color campaign in the MP5 archive.

In addition, the subdirectory clr_footprints/clr_targets (RTM volume) contains three shapefiles for 3-, 8-, and 11-color targets.

Color-set polygon attributes contained in shapefiles include the following"

Š         start_obs[INT] -- first observation ID (in time) for this set

Š         obs_list -- list of all observation ID's in the set

Š         src_shp -- image footprint shapefile used to generate this record

Š         seq_type -- campaign the sequence belongs to, i.e. MDR WAC 8-bands

Š         seq_length[INT] -- number of images in colorset sequence

Š         seq_hscale[FLOAT] -- horizontal pixel scale of first image

Š         seq_i[FLOAT] -- solar incidence of center pixel in first image

Š         seq_p[FLOAT] -- solar phase of center pixel in first image

Š         seq_e[FLOAT] -- emission angle of center pixel in first image

Š         mdr_metric[FLOAT] -- 8-color map quality score for first image

Š         site_id[INT] -- for targeted images, the ID of the site of interest

Š         det_temp[FLOAT] -- detector temperature of first image in degC

 

The extras directory in the RTM archive also contains a list of all SITE_IDs targeted by MDIS or other instruments, describing their latitude/longitude coordinates and the motivation for their targeting. This list is derived directly from the list of observing requests for targeted images compiled by the MESSENGER science and operations team and the original file had an uneven level of detail.  The file EXTRINFO.TXT describes the contents of the file.

4. Applicable Software

4.1 Utility Programs

Standard Integrated Software for Imagers and Spectrometers (ISIS) tools (http://isis.astrogeology.usgs.gov/) can be used to work with the data.  ISIS has the ability to calibrate EDRs, incorporate related SPICE files, and map-project images. ISIS was also used to generate the global DEM onto which end-of-mission map products were projected, as described by Becker et al. (2016) [Applicable Document 15].

Environment for Visualizing Images (ENVI) software from Exelis, Inc. (http://www.exelisinc.com/solutions/ENVI/Pages/default.aspx) is widely used for analysis of multispectral data products such as MDRs, MD3s, MP5s, and WAC-derived RTMs.

4.2 Applicable PDS Software Tools

PDS-labeled images and tables can be viewed with the program NASAView, developed by the PDS and available for a variety of computer platforms from the PDS web site http://pds.nasa.gov/tools/nasa-view.shtml.

4.3 Tutorial information

User tutorials on the details of MDIS data products and how to open and process them with ISIS and other software are available online at the PDS, at http://pds-imaging.jpl.nasa.gov/software/.

 


Appendix A. Data Archive Terms

 

Archive

 

An archive consists of one or more data sets along with all the documentation and ancillary information needed to understand and use the data. An archive is a logical construct independent of the medium on which it is stored.

Archive volume, archive volume set

 

A volume is a unit of medium on which data products are stored; for example, one DVD. An archive volume is a volume containing all or part of an archive; that is, data products plus documentation and ancillary files. When an archive spans multiple volumes, they are called an archive volume set. Usually the documentation and some ancillary files are repeated on each volume of the set, so that a single volume can be used alone.

Calibrated Data Records (CDRs)

Image data calibrated to radiance, or processed further to I/F or I/F corrected to i = 30ľ, e = 0ľ (NAC or WAC). CODMAC level 4.

Data Product

 

A labeled grouping of data resulting from a scientific observation, usually stored in one file. A product label identifies, describes, and defines the structure of the data. An example of a data product is a planetary image, a spectrum table, or a time series table.

Data Set

 

An accumulation of data products. A data set together with supporting documentation and ancillary files is an archive.

Derived Data Records (DDRs)

Geometric data registered to non-map-projected image data and used for correction from I/F to I/F corrected to i = 30ľ, e = 0ľ (NAC or WAC). CODMAC level 6.

Experiment Data Records (EDRs)

Non-map-projected raw data (NAC or WAC). CODMAC level 2.

Map Projected Basemap Reduced Data Records (BDRs)

Map-projected I/F, I/F corrected to i = 30ľ, e = 0ľ, and relevant DDR layers (NAC or WAC filter 7). CODMAC level 5.

(8-color) Map Projected Multispectral Reduced Data Records (MDRs)

Map-projected I/F, I/F corrected to i = 30ľ, e = 0ľ, and relevant DDR layers (WAC filters 1, 3-12). CODMAC level 5.

(3-color) Map Projected Multispectral Reduced Data Records (MD3s)

Map-projected I/F, I/F corrected to i = 30ľ, e = 0ľ, and relevant DDR layers (WAC filters 6, 7, and 9). CODMAC level 5.

(5-Color) Map Projected Multispectral Reduced Data Records (MP5s)

Map-projected I/F, I/F corrected to i = 30ľ, e = 0ľ, and relevant DDR layers (WAC filters 4, 6, 7, 9, and 12). CODMAC level 5.

Map Projected High-incidence Angle Basemap Illuminated from the East Reduced Data Records (HIEs)

Map-projected I/F, I/F corrected to i = 30ľ, e = 0ľ, and relevant DDR layers (NAC or WAC filter 7). CODMAC level 5.

Map Projected High-incidence Angle Basemap Illuminated from the West Reduced Data Records (HIWs)

Map-projected I/F, I/F corrected to i = 30ľ, e = 0ľ, and relevant DDR layers (NAC or WAC filter 7). CODMAC level 5.

Map Projected Low-incidence Angle Basemap Reduced Data Records (LOIs)

Map-projected I/F, I/F corrected to i = 30ľ, e = 0ľ, and relevant DDR layers (NAC or WAC filter 7). CODMAC level 5.

Map Projected Regional Targeted Mosaic Reduced Data Records (RTMs)

Map-projected I/F, I/F corrected to i = 30ľ, e = 0ľ, and relevant DDR layers (NAC or WAC filters 1, 3-12). CODMAC level 5.

Standard data product

 

A data product defined during the proposal and selection process and that is contractually promised by the PI as part of the investigation. Standard data products are generated in a predefined way, using well-understood procedures, and processed in “pipeline” fashion.

Special data product

A data product of special interest that may require subjective judgment to produce and may not be produced in a pipeline fashion. Special products are produced as resources permit.


APPENDIX B. LABEL AND HEADER DESCRIPTIONS

 

The keywords listed below appear in the example labels found in Appendices C – L.

 

PDS_VERSION_ID

The version number of the PDS standards document that is valid when a data product label is created. PDS3 is used for the MESSENGER Data products.

 

 

File format parameters

 

RECORD_TYPE

The record format of a file.

 

RECORD_BYTES

The number of bytes in a physical file record, including record terminators and separators.

 

FILE_RECORDS

The number of physical file records, including both label records and data records.     

 

LABEL_REVISION_NOTE

Provides information regarding the revision status and authorship of a PDS label.

 

^IMAGE

The pointer to a full image object.  This object contains all the sub-frames which correspond to a given observation.  The sub-frames are arrayed in their respective positions corresponding to a full frame observation. The value contains the starting record position in the file.

 

 

General data description parameters

 

MISSION_NAME

Identifies the MESSENGER planetary mission.

 

INSTRUMENT_HOST_NAME

The full, unabbreviated name of the spacecraft.

 

DATA_SET_ID

Uniquely identifies the data sets available on the volume.

 

DATA_QUALITY_ID

A data quality index is used to encode figures-of-merit into one parameter that is included in the label of each CDR or DDR. The 16-byte data quality index is interpreted as follows:

 

Byte 0: Image source is CCD.

1 = Image source is test pattern as indicated by

MESS:SOURCE=1=Test pattern or

MESS:SOURCE=2=Inverted test pattern.

0 = Image source is CCD as indicated by MESS:SOURCE=0=CCD.

 

Byte 1: Valid exposure time.

1 = Exposure time in ms as indicated by MESS:EXPOSURE equals 0 ms (during cruise) or is less than or equal to 2 ms (orbit).

0 = Exposure time in ms as indicated by MESS:EXPOSURE is greater than or equal to minimum valid value.

 

Byte 2: Presence of an excessive number of pixels at or approaching saturation.

 

As saturation is approached responsivity decreases, and signal becomes nonlinear with brightness for small sources. Saturation can be exceeded for very bright or large sources once pixel antiblooming is overwhelmed. The raw 12-bit DN level indicative of the onset of saturation varies between the two CCDs. In the WAC (MESS:IMAGER=0) it is approximately 3600; in the NAC (MESS:IMAGER=1) it is approximately 3400. If a LUT has been used to convert 12-bit to 8-bit DN, then an 8-bit DN value of 255 also indicates saturation. An 8-bit 255 is encountered before saturation of the 12-bit DN in the case of LUT 1. In autoexposure mode, the typical threshold for the allowable number of saturated pixels is 5 pixels. In manual exposure mode the number of saturated pixels is uncontrolled.

 

1 = There are > 5 pixels exceeding the DN indicating onset of saturation.

0 = There are < 5 pixels exceeding the DN indicating onset of saturation.

 

Byte 3: Valid pivot position.

1 = Pivot position not valid, as indicated by pivot position validity flag MESS:PIV_PV=0=invalid

0 = Pivot position valid as indicated by both keywords having a value of 1=valid.

 

Byte 4: Filter wheel in position (WAC only; requires MESS:IMAGER=0, or else value of this byte = 0).

1 = Filter wheel not in position, as indicated by any of three conditions:

(a) filter wheel position validity flag MESS:FW_PV=0=invalid,

(b) filter wheel reading validity flag MESS:FW_RV=0=invalid, or

(c) an excessive difference between filter wheel resolver goal and actual position as given in table below.

0 = Filter wheel in position as indicated by an allowable difference between goal and position, and by both MESS:FW_PV=1 and MESS:FW_RV=1 (See Table B-1).

 

 

 

 

 

 

 

 

Table B-1:  Filter wheel encoder positions

FILTER_NUMBER

MESS:FW_GOAL

Allowable (abs(MESS:FW_POS - MESS:FW_GOAL))

1

17376

+/- 500

2

11976

+/- 500

3

6492

+/- 500

4

1108

+/- 500

5

61104

+/- 500

6

55684

+/- 500

7

50148

+/- 500

8

44760

+/- 500

9

39256

+/- 500

10

33796

+/- 500

11

28252

+/- 500

12

22852

+/- 500

 

 

Byte 5: Quality of spacecraft attitude knowledge.

1 = Spacecraft attitude knowledge is bad (MESS:ATT_FLAG is in the range 0-3).

0 = Spacecraft attitude knowledge is good (MESS:ATT_FLAG is in the range 5-7).

 

Byte 6: CCD temperature range.

1 = CCD out of temperature range at which performance is well calibrated (MESS:CCD_TEMP is outside a range of between 1005 and 1130, which for the WAC is -45C to -11 C, and for the NAC is -48C to -14C).

0 = CCD within well calibrated temperature range (MESS:CCD_TEMP is within the stated range).

 

Byte 7: Completeness of data within the commanded selection of subframes or full frame.

Missing frames or portions of frames are indicated in an EDR with a value of 0 (this cannot be a valid data value).

1 = There are missing data (some pixels populated with 0).

0 = There are no missing data.

 

Bytes 8-15: spare.

 

PRODUCT_ID

The permanent, unique identifier assigned to a data product by its producer. In the PDS, the value assigned to product_id must be unique within its data set.

 

PRODUCT_TYPE

Identifies the type or category of a product within the data set.

 

PRODUCT_VERSION_ID

Identifies the version of an individual product within the data set.

 

 

 

SOURCE_PRODUCT_ID

This is a set of input files used as input to create this product.  The first element is the original spacecraft solid state recorder (SSR) filename as downlinked.  Additional elements are the SPICE kernels used to produce the ancillary data.

 

PRODUCER_INSTITUTION_NAME

The organization responsible for developing the data products.

 

SOFTWARE_NAME

The name of the software system that created the data products. The version number of the software is identified by the SOFTWARE_VERSION_ID keyword.

 

SOFTWARE_VERSION_ID

Version of the software used to generate the data products.

 

MISSION_PHASE_NAME

Provides the commonly-used identifiers of the MESSENGER Mission Phase. These are (From MESSENGER Data Management and Archiving Plan [Applicable Document 4]):

 

EARTH CRUISE

EARTH FLYBY

VENUS 1 CRUISE

VENUS 1 FLYBY

VENUS 2 CRUISE

VENUS 2 FLYBY

MERCURY 1 CRUISE

MERCURY 1 FLYBY

MERCURY 2 CRUISE

MERCURY 2 FLYBY

MERCURY 3 CRUISE

MERCURY 3 FLYBY

MERCURY 4 CRUISE

MERCURY ORBIT

MERCURY ORBIT YEAR 2

MERCURY ORBIT YEAR 3

MERCURY ORBIT YEAR 4

MERCURY ORBIT YEAR 5

 

TARGET_NAME

Identifies the target. (Such as: MERCURY, VENUS, EARTH, MOON, OTHER).

 

SEQUENCE_NAME

Identifies the imaging sequence name.

 

OBSERVATION_ID

Image counter from header.

  

OBSERVATION_TYPE

The imaging campaign of which the image is a part. This can be one or more of the following values:

Š         Albedo (either a NAC image or a WAC 750-nm filter image, part of global mapping during the extended mission, with a goal of near-nadir pointing and low to moderate solar incidence angle)

Š         Albedo,Albedo Stereo (either a NAC image or a WAC 750-nm filter image, part of global mapping during the extended mission, with a goal of off-nadir pointing and low solar incidence angle at the same local solar time as Albedo imaging to serve as a stereo complement)

Š         Co-align Calibration (pairs of NAC and WAC clear filter images acquired over the course of the mission to track relative pointing of the cameras and to determine camera focal length and distortion parameters as a function of temperature)

Š         Color (8-color WAC image sets, part of global 8-color mapping with a goal of near-nadir pointing and low solar incidence angle)

Š         Color,Emission Phase Function (sets of multispectral images of a specific feature acquired over 1 or 2 orbits at multiple pivot positions, to measure spatial variations of surface photometric properties)

Š         Color,Southern Polar (repeated 8-color image sets of mid-southern latitudes along the sub-solar longitude, taken to track time variation in WAC responsivity - late augmented to Southern Polar,Eleven Color)

Š         Color,Targeted (3-color observations of select features acquired early in the mission at higher spatial resolution than the 8-color map, plus selected 8-color sets pointed at specific regions to measure Mercury's photometric function)

Š         Comet (images of Comet ISON and Encke)

Š         Dark Current (NAC or WAC 430-nm filter images taken with MDIS stowed - discontinued in Mercury orbit due to light leaking into system in stowed position)

Š         Dark Polar Craters (NAC or clear filter WAC images near or including permanently shadowed polar regions, taken as part of a search for features illuminated indirectly by sunlight crater walls, and limited 3-color images)

Š         Eleven Color,NAC WAC Calibration (11-color image sets of Mercury acquired to use landmarks in the images to determine differences filter to filter in pointing and geometric distortion)

Š         Engineering (images with no dedicated science purpose)

Š         High Incidence (either a NAC image or a WAC 750-nm filter image, part of global mapping during the extended mission with a goal of near-nadir pointing and solar incidence angle near 80 degrees)

Š         Limb (always a WAC 750-nm filter image, taken in groups from high orbit for one of two purposes: to fit planet shape, or to image exosphere)

Š         Monochrome (either a NAC image or a WAC 750-nm filter image, part of global mapping during the primary mission, with a goal of near-nadir pointing and solar incidence angle near 68 degrees)

Š         Monochrome,Oblique (high emission angle images of selected area of Mercury for profile views of high-relief features)

Š