Introduction to the Mars Global Surveyor
Science Sampler Data Set Collection


June 26, 1998

  1. Introduction
  2. CD-ROM Format
  3. File Formats
  4. CD-ROM Contents
  5. Whom to Contact for Information
  6. Cognizant Persons

1. Introduction

This document provides an overview of the Mars Global Surveyor Science Sampler, including a complete listing of the contents of the volume, below. To begin browsing the science data immediately, use a Web browser to open the file INDEX.HTM in the BROWSE directory. For a detailed discussion of the contents of this volume, see the file VOLINFO.TXT in the DOCUMENT directory (or its hypertext equivalent, VOLINFO.HTM).

This volume contains science data products mainly from observations acquired by Mars Global Surveyor (MGS) instruments between October 13 and November 7, 1997 (MGS orbits 19 through 36). These orbits correspond to the Assessment Subphase of the Orbit Insertion Phase of the mission. During this period, the aerobraking procedure used to place the spacecraft in a circular mapping orbit was suspended because of apparent damage to one of the solar array panels. The spacecraft periapsis was raised from 110 to about 172 kilometers on October 13, reducing atmospheric drag on the panels. Analyses conducted during the period from October 13 to November 7, 1997, showed that aerobraking remained feasible, but that it had to be done more slowly than before, at a higher periapsis altitude. During the Assessment Subphase, the spacecraft instruments were pointed toward the surface during close approach and science data were acquired. Aerobraking resumed on November 8 with a periapsis altitude of 120 km.

The periapsis was again raised on March 27, 1998, to avoid aerobraking during solar conjunction and to allow for appropriate phasing of the final circular orbit. As of this writing, aerobraking is scheduled to begin again on September 12, 1998, and continue through mid-March, 1999, followed by one Mars year of mapping operations with a 400 kilometer average altitude circular orbit and a 2 AM equator crossing time. The period from March 27 until September 12, 1998, is called the Science Phasing portion of the mission. Science data will be collected during periapsis passes during this time by pointing the instruments toward the planet.

The Science Sampler Collection is intended to provide users with samples of MGS data products from each instrument, to allow them to prepare for data products that will be delivered routinely after MGS achieves its mapping orbit in March 1999. The collection includes MGS data products from the Mars Orbiter Camera (MOC), the Mars Orbiter Laser Altimeter (MOLA), the Thermal Emission Spectrometer (TES), and the Magnetometer / Electron Reflectometer (MAG/ER). It also includes two gravity models of Mars based on Mariner 9 and Viking data, which will be updated with the results of the MGS Radio Science Subsystem (RSS) observations. (No RSS data were collected during the Assessment Subphase, and none were available for release when this sampler collection was being assembled.) Finally, SPICE kernels and orbit nadir ground track files are included to allow the user to understand where data were acquired during the Assessment Subphase of the mission.

Data products in this collection range from standard products in archival format, such as the MOLA PEDRs, to highly derived products in a form convenient for viewing but not necessarily intended for data analysis, such as the MAG/ER plots. It should be noted that most products in this collection were generated specifically for this publication and do not constitute an official MGS standard product delivery. These data will be re-released later in standard product form. Detailed descriptions of the product content and formats may be found in the VOLINFO.TXT file (or its hypertext equivalent, VOLINFO.HTM) in the DOCUMENT directory of this volume.

2. CD-ROM Format

The CD-ROM has been formatted so that a variety of computer systems (e.g., PC, Macintosh, and Sun) may access the data. Specifically, it is formatted according to the ISO-9660 level 1 Interchange Standard. For further information, refer to the ISO-9660 Standard Document: RF# ISO 9660-1988, April 15, 1988.

This CD-ROM does not contain any Extended Attribute Records (XAR). Thus, VAX/VMS users may have some problems accessing files on this volume.

3. File Formats

The documentation and data on this volume are presented both in Planetary Data System (PDS) formats and in formats accessible through Web browser software (HTML documents and GIF images). The BROWSE directory contains a set of hypertext (HTML) files and reduced versions of some data products, with links to the actual data products. This allows the user to explore the Science Sampler using a Web browser.

All documentation, detached PDS label, and hypertext files on this volume are stream format files, with a carriage return (ASCII 13) and a line feed character (ASCII 10) at the end of the record. This allows the files to be read by the MacOS, DOS, UNIX, and VMS operating systems. All of these files can be viewed with a Web browser.

All images on this volume are in GIF format, except the Radio Science gravity map. While GIF will not be used as an archive format for standard products on future volumes, it is used on the Science Sampler to provide a convenient means for a quick look at the data, as GIF images can easily be viewed with a Web browser. Data in tabular form can also be viewed in a Web browser but might be more conveniently used when loaded into a spreadsheet program. The accompanying PDS labels for these files contain descriptions of the table format. The only data products not directly viewable in a Web browser are the MOLA AEDR and PEDR binary files. However, ASCII text versions of the PEDRs in tabular form have been provided.

Note that to view PDS labels and table data in a Web browser, the browser may need to be configured to recognize files with extensions ".LBL" and ".TAB" as text files.

The PDS program NASAView can be used to display tables and PDS-labeled images. At this writing the current version of NASAView is 1.2b (beta). NASAView is expected to be revised in the near future to support display of GIF images. The software is available at no cost from the PDS web site , under Data and Services.

Each data file on this volume is described by a PDS label, either embedded at the beginning of the file or detached in a separate file of the same name but with the extension ".LBL". For example, the file AP00021V.TAB is accompanied by the detached label file AP00021V.LBL in the same directory.  Additional information about PDS labels is found in the Planetary Data System Standards Reference, version 3.2, July 24, 1995, JPL D-7669.

4. CD-ROM Contents

Files on this CD-ROM are organized into a series of subdirectories below the top-level directory. The following table shows the structure and content of these directories. In the table, directory names are enclosed in square brackets ([]).

      FILE                  CONTENTS

  Top-level directory
   |- AAREADME.TXT          Plain text version of AAREADME.HTM.
   |- AAREADME.HTM          The file you are reading.
   |- ERRATA.TXT            Comments and errata on this CD-ROM.
   |- VOLDESC.CAT           Description of the contents of this CD-ROM
   |                        volume in object format.
   |- [BROWSE]              Directory containing HTML files and reduced
   |   |                       versions of data products for browsing
   |   |                       the volume.
   |   |- BROWSE.LBL        PDS label for HTML files in this directory.
   |   |- INDEX.HTM         Starting HTML file for browsing.
   |   |- *.HTM             Additional HTML files.
   |   |- [IMAGES]          Images referenced by the *.HTM files.
   |   |- [MAGER]           HTML files for browsing MAG/ER data.
   |   |- [MOC]             HTML files and browse images for MOC.
   |   |- [MOLA]            HTML files and images of MOLA
   |   |                       topography profiles derived from the 
   |   |                       MOLA PEDR data products.
   |   |- [TES]             HTML files and browse images for TES.
   |- [CATALOG]             Directory containing PDS catalog objects.
   |   |- CATINFO.TXT       Description of files in the CATALOG directory.
   |   |- DSMAP1.CAT        Data set map projection object for browse
   |   |                    images showing MOC data product locations.
   |   |- DSMAP2.CAT        Data set map projection object for RSS
   |   |                    gravity map.
   |   |- REF.CAT           Reference objects mentioned in DSMAP2.CAT.
   |- [DOCUMENT]            Directory containing documentation files.
   |   |- AEDRSIS.HTM       Hypertext version of MOLA AEDR Software
   |   |                       Interface Specification (SIS).
   |   |- AEDRSIS.LBL       PDS label for AEDRSIS.HTM and AEDRSIS.PDF.
   |   |- AEDRSIS.PDF       Adobe Acrobat version of MOLA AEDR SIS.
   |   |- DOCINFO.TXT       Description of files in DOCUMENT directory.
   |   |- PEDRSIS.HTM       Hypertext version of MOLA PEDR Software
   |   |                       Interface Specification (SIS).
   |   |- PEDRSIS.LBL       PDS label for PEDRSIS.HTM and PEDRSIS.PDF.
   |   |- PEDRSIS.PDF       Adobe Acrobat version of MOLA PEDR SIS.
   |   |- VOLINFO.TXT       Overview of the mission, the instruments,
   |   |                       and the archiving process.
   |   |- VOLINFO.HTM       Hypertext version of VOLINFO.TXT.
   |- [GEOMETRY]            Directory containing SPICE kernels and ground 
   |   |                       track data.
   |   |- GEOMINFO.TXT      Description of files in the GEOMETRY directory.
   |   |- ORBnnnnC.TAB      Ground tracks for orbit nnnn in planetocentric
   |   |                       coordinates.
   |   |- ORBnnnnG.TAB      Ground tracks for orbit nnnn in planetographic
   |   |                       coordinates.
   |   |- ORBITSUM.TAB      Time and geometry parameters for each orbit.
   |   |- *.LBL             PDS labels for files in this directory.
   |   |- [PC]              Directory containing SPICE kernels for the PC.
   |   |   |- M*.BC         SPICE CK kernels; spacecraft orientation for 
   |   |                       orbits corresponding to data on this volume.
   |   |   |- DE403S.BSP    SPICE SPK (ephemeris) kernel for Mars.
   |   |   |- MGS_AERO.BSP  SPICE SPK (ephemeris) kernel for MGS 
   |   |   |                   spacecraft.
   |   |   |- MGS_SCLK.TSC  SPICE SCLK (spacecraft clock) kernel.
   |   |   |- NAIF0006.TLS  SPICE LSK (leapseconds) kernel.
   |   |   |- PCK00006.TPC  SPICE PCK kernel; size/shape/orientation for 
   |   |   |                   Mars.
   |   |   |- *.LBL         PDS labels for SPICE kernels.
   |   |- [UNIX]            Directory containing SPICE kernels for UNIX
   |                           (same file names as in the PC directory).
   |- [INDEX]               Directory containing index files.
   |   |- INDXINFO.TXT      Description of files in the INDEX directory.
   |   |- INDEX.TAB         Index table for data products on the volume.
   |   |- INDEX.LBL         PDS label for INDEX.TAB
   |- [LABEL]               Directory containing format files
   |   |                       referenced by data product labels.
   |   |- LABINFO.TXT       Description of files in the LABEL directory.
   |   |- MOLAMNT.FMT       Describes the format of an AEDR Maintenance 
   |   |                       Mode table.
   |   |- MOLASCCT.FMT      Describes the format of the COUNTS
   |   |                       container in an AEDR frame.
   |   |- MOLASCFR.FMT      Describes the format of an AEDR frame.
   |   |- MOLASCI.FMT       Describes the format of an AEDR Science 
   |   |                       Mode table.
   |   |- PEDRENGn.FMT      Describe the format of the second section
   |   |                       of a PEDR, where n=1 through 7. Seven 
   |   |                       different record formats are possible,
   |   |                       depending on which of seven frames is
   |   |                       recorded.
   |   |- PEDRSEC1.FMT      Describes the format of the first section
   |   |                       of a PEDR.
   |   |- PEDRSEC3.FMT      Describes the format of the third section
   |                           of a PEDR.
   |- [MAGER]               MAG/ER data product directory.
   |   |- MAGnnnnP.GIF      MAG/ER products, where nnnn=orbit number.
   |   |- MAGnnnnP.LBL      PDS labels for MAGnnnnP.GIF.
   |- [MOC]                 MOC data product directory.
   |   |- NAnnnnxx.GIF      MOC data products, where nnnn=orbit number
   |   |                       and xx=image number within orbit.
   |   |- NAnnnnxx.LBL      PDS labels for NAnnnnxx.GIF.
   |- [MOLA]                MOLA data product directory.
   |   |- [AEDR]            Directory of MOLA AEDR data products.
   |   |   |- AAnnnnnF.B    AEDR data, where nnnnn=orbit number.
   |   |
   |   |- [PEDR]            Directory of MOLA PEDR products in 
   |   |   |                   their original binary format.
   |   |   |- APnnnnnV.B    PEDR data, where nnnnn=orbit number.
   |   |
   |   |- [PEDR_ASC]        Directory of MOLA PEDR products converted
   |       |                   to ASCII tables for easier access.
   |       |- APnnnnnV.TAB  PEDR tables, where nnnnn=orbit number.
   |       |- APnnnnnV.LBL  PDS labels for APnnnnnV.TAB.
   |- [RSS]                 RSS data product directory (pre-MGS
   |   |                       gravity models).
   |   |- [IMG]             Gravity image data.
   |   |   |- JGM50C01.IMG  Map of JPL gravity model.
   |   |   |- JGM50C01.LBL  PDS label for JGM50C01.IMG.
   |   |
   |   |- [SHA]             Gravity models in ASCII tabular format.
   |       |- GGM50A01.SHA  Spherical harmonics gravity model produced
   |       |                   by GFSC Gravity Science Team.
   |       |- GGM50A01.LBL  PDS label for GGM50A01.SHA.
   |       |  JGM50C01.SHA  Spherical harmonics gravity model produced
   |       |                   by JPL Gravity Science Team.
   |       |- JGM50C01.LBL  PDS label for JGM50C01.SHA.
   |- [TES]                 TES data product directory.
       |- [RADIANCE]        Directory of calibrated radiance products.
       |   |- TESnnnnR.TAB  Calibrated radiance data products, where
       |   |                   nnnn=orbit number.
       |   |- TESWAVEN.TAB  TES wave number file.
       |   |- TESWAVEN.LBL  PDS label for TESWAVEN.TAB.
       |- [TEMPIMG]         Directory of temperature images.
           |- TESnnnnT.GIF  25-micron temperature images.
           |- TESnnnnT.LBL  PDS labels for TESnnnnT.GIF.
           |- TESROLL.TAB   Time and location for each spacecraft
           |                   rotation (roll) corresponding to 
           |                   temperature images.
           |- TESROLL.LBL   PDS label for TESROLL.TAB.

5. Whom to Contact for Information

For questions concerning this data set collection:

PDS Geosciences Node
Washington University
Dept. of Earth and Planetary Sciences
1 Brookings Drive
St. Louis, MO 63130

WWW Site:
Electronic mail address:

6. Cognizant Persons

MAG/ER data were provided by Mario Acuna, MAG/ER Principal Investigator, with assistance from John Connerney, both of NASA/Goddard Space Flight Center.

MOC data were provided by Michael Malin, MOC Principal Investigator, Malin Space Science Systems, with assistance from Eric Eliason, USGS/Flagstaff.

MOLA data were provided by David Smith, MOLA Principal Investigator, with assistance from Greg Neumann, both of NASA/Goddard Space Flight Center, and Peter Ford, MIT.

The pre-MGS Radio Science gravity models were provided by David Smith with help from Frank G. Lemoine, NASA/GSFC, and by William L. Sjogren with help from Alex Konopliv, Jet Propulsion Laboratory.

TES data were provided by Philip Christensen, TES Principal Investigator, with assistance from Noel Gorelick, Greg Mehall, and Kelly Bender, Arizona State University.

MGS orbit track data were provided by Charles Acton and Boris Semenov, Navigation and Ancillary Information Facility (NAIF), Jet Propulsion Laboratory.

Documentation was provided by the above individuals, Frank Palluconi, Jet Propulsion Laboratory, and Richard Simpson, Stanford University.

This volume was designed and produced by Susan Slavney, Edward A. Guinness, Raymond E. Arvidson, Jim Alexopoulos, Thomas C. Stein, and Rebecca Eby, Planetary Data System Geosciences Node, Washington University, St. Louis, Missouri.