MARS GLOBAL SURVEYOR
Mars Orbiter Laser Altimeter
MOLA EXPERIMENT GRIDDED DATA RECORD
SOFTWARE INTERFACE SPECIFICATION
(MOLA EGDR SIS)
MGS-M-MOLA-5-IEGDR-L3-V1.0
MGS-M-MOLA-5-MEGDR-L3-V1.0
Version 2.0
November 23, 1999
NASA Goddard Space Flight Center
Wallops Flight Facility
Wallops Island, VA 23337
Submitted: | ________________________________ Gregory A. Neumann MOLA Science Team |
_______________ Date |
Concurred: | ________________________________ Maria Zuber MOLA Deputy Principal Investigator |
_______________ Date |
Approved: | ________________________________ David E. Smith MOLA Principal Investigator |
_______________ Date |
Document and Change Control Log |
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Date |
Version |
Section |
Status |
03/31/97 | 1.0 | all | Released for Mars Global Surveyor |
11/23/99 | 1.0 | all | Revised for new products format |
Section |
Table of Contents |
1.0 | Introduction |
1.1 | Purpose |
1.2 | Scope |
1.3 | Applicable Documents |
1.4 | Functional Description |
1.4.1 | Data Content Summary |
1.4.2 | Source and Transfer Method |
1.4.3 | Recipients and Utilization |
1.4.4 | Pertinent Relationships with Other Interfaces |
1.5 | Assumptions and Constraints |
2.0 | Environment |
2.1 | Hardware Characteristics and Limitations |
2.2 | Interface Medium and Characteristics |
2.3 | Failure Protection, Detection, and Recovery Features |
2.3.1 | Backup Requirements |
2.3.2 | Security / Integrity Measures |
2.4 | End-Of-File (or Medium) Convention |
3.0 | Access |
3.1 | Access Tools |
3.2 | Input / Output Protocol |
3.3 | Timing and Sequencing Characteristics |
3.4 | PDB Information |
4.0 | Detailed Interface Specifications |
4.1 | Labeling and Identification |
4.2 | Structure and Organization Overview |
4.3 | Volume, Size, and Frequency Estimates |
Appendix A | Acronyms |
Appendix B | Example EGDR Label |
The MOLA Science Team is required to create, validate, and archive the MOLA standard data products. To define each standard data product, the MOLA Science Team is required to provide a Software Interface Specification (SIS). The SIS shall describe the data product contents and define the record and data format. The Planetary Data Systems (PDS) Geosciences Node has agreed to archive the MOLA standard data products. The MOLA archive volume shall be described in a separate SIS. The MOLA standard science data products are the Aggregated Experiment Data Record all MOLA raw data aggregated by orbit; Precision Experiment Data Record MOLA science data processed into profiles with precision orbit locations added; and the Experiment Gridded Data Record MOLA gridded data in two different densities. This SIS shall define the Experiment Gridded Data Record Data Product. The term EGDR Data Product refers to the generic data product as all densities have the same format. The densities to be delivered by the Science Team are defined in this document.
This document generically describes the format and contents of the EGDR Data Product.
The description in this SIS can be applied to all densities of the EGDR Data Product. Where necessary, comments appropriate to the specific densities of EGDR Data Products are included. Also, the EGDR Data Product software, hardware, and human interfaces shall be mentioned in order to describe the interface; the actual software, hardware, or human node on the other side of the interface shall be described in detail in its own interface or other reference document.
1. |
MOLA-672-PL-89.354 |
Operations Facility Configuration and Control Plan, Version 1.0, NASA Goddard Space Flight Center Wallops Flight Facility, January 5, 1990 |
2. |
SFOC-0088-00-06-02 |
Space Flight Operations Center User's Guide for Work Station End Users, Volume 2: Working with File Data, Version 17.0, Draft, Jet Propulsion Laboratory, January 1992 |
3. |
MO-642-3-PDB-UG-01 |
Mars Observer Project Database (MO PDB) User Overview, Strawman, Jet Propulsion Laboratory, February 7, 1990 |
4. |
MOSO0099-04-00 |
Planetary Science Data Dictionary Document, PDS Version 3.0, Jet Propulsion Laboratory, November 20,1992, JPL D-7116, Rev C |
5. |
MOLA-972-SP-92.230 |
Mars Orbiter Laser Altimeter Precision Experiment Data Record Product Software Interface Specification Document, Version 2.718, NASA Goddard Space Flight Center Wallops Flight Facility, October 14, 1999 |
6. |
Mars Observer Cartography White Paper, Draft, Version 1.0, R. E. Arvidson, E. A. Guinness, T. A. Duxbury, December 15, 1992 | |
7. |
MOLA-972-SP-92.213 |
MOLA Standard Product Archive Volume Software Interface Specification, Version 4.3, S. Slavney, R. E. Arvidson, Washington University, November 18, 1999 |
The EGDR data product contains the mapped collection of MOLA science data. The gridded products are created by binning data from the PEDR Data Products into maps covering the entire planet. A gridded product is stored as an ASCII table with one row per data bin. The table has columns for mean observed planetary radius, areoid radius, median observed topography, and number of observations in the bin. The EGDR is generated in two resolutions: the IEGDR (Initial EGDR) product has 1º by 1º bins, and the MEGDR (Mission EGDR) product has 0.25º by 0.25º degree bins. The EGDR Data Product is described further in Section 4.0.
The EGDR Data Product is created from the PEDR Data Products. The data are binned into cells using a series of active image grid map files. After creation, the EGDR Data Product shall be transferred to the MOLA Science Operations Planning Computer (SOPC) for transfer to the PDS Geosciences Node. The EGDR Data Product shall remain available to the MOLA Science Team on the MOLA operations file system.
The PDS Geosciences Node will receive the EGDR data product and make it available to the science community.
The EGDR data product shall remain on the MOLA operations file system and be available to the MOLA science team for further analysis.
The EGDR data product is created from the Precision Experiment Data Record (PEDR) data product. Any changes to the PEDR data product can affect the EGDR data product format or content. Changes in the PEDR aggregation frequency or scheduled availability can cause changes to the EGDR Data Product's availability or density. See applicable document #5 for a detailed description of the PEDR Data Product.
Any changes to the EGDR data product, either format or content, shall also affect the software that creates the data product.
The EGDR data product contains only data elements collected from MOLA science mode data.
Not applicable.
The EGDR data product shall be produced on computer(s) within the MOLA operating environment. The EGDR data product shall be transferred to the MOLA SOPC via FTP in preparation for distribution to the PDS Geosciences Node for archival. The SOPC architecture is described in applicable document #1.
The EGDR data product will be backed up on magnetic media on the MOLA operations file system via the MOLA operations back-up plan. The EGDR Data Product will be archived to CD-ROM by the PDS Geosciences Node. The MGS Project Data Base will be available as an additional backup location.
Refer to applicable document #1 for a description of the MOLA operations system security and integrity plan.
The EGDR Data Product is an ASCII file with fixed-length records. Each record ends with a carriage return followed by a line feed. The end of an EGDR Data Product is detected by the end-of-file marker.
The MOLA Science Team shall have access to the EGDR data product on the MOLA operations file system via FTP. The science community will have access to the EGDR Data Product through the Archive Volume produced by the PDS Geosciences Node and should obtain the MOLA Archive Volume SIS for information on data access. The MOLA Science Team will not provide the PDS any special tools to access the EGDR Data Product.
N/A
There will be two deliveries of MOLA Experiment Gridded Data Products Initial and Mission. The format of the data in the deliveries is the same; the density of the data is different. The Initial Experiment Gridded Record (IEGDR) Data Product has 1 degree by 1 degree cells, and the Mission Experiment Gridded Data Record (MEGDR) Product has 0.25 degree by 0.25 degree cells. The density of the images is determined by the amount of mapping data used in the gridding process.
The IEGDR data product requires a period of nominally 70 days to generate and covers the first 90 mapping days (all data acquired through May 31, 1999). The MEGDR data product requires a period of nominally 761 days to generate and covers the entire mapping mission which shall be approximately 687 days. Each completed EGDR data product will be examined by the MOLA Science Team for product quality control and validation. Upon team approval, the EGDR data product is delivered to the PDS Geosciences Node for archive.
The EGDR Data Product will be stored in the Science category as a science data product in the Mars Global Surveyor PDB. See applicable document #3 for an end user overview of the PDB. The PDB catalog attributes (as part of the K-header) are listed and described below in section 4.3.1.2.
The data set IDs for the MOLA EGDR Data Products are:
MO-M-MOLA-5-IEGDR-L3-V1.0 Initial Experiment Gridded Data Record
MO-M-MOLA-5-MEGDR-L3-V1.0 Mission Experiment Gridded Data Record.
These are the data set IDs that were provided to the PDB and the Planetary Data System. These IDs describe the EGDR data product level and version number. The version number is incremented should the EGDR Data Product format change.
The required catalog keywords for the EGDR Data Products are:
PDS_VERSION_ID RECORD_TYPE FILE_RECORDS LABEL_RECORDS RECORD_BYTES DATA_SET_ID FILE_NAME PRODUCT_ID SOFTWARE_NAME UPLOAD_ID SOURCE_PRODUCT_ID PRODUCT_RELEASE_DATE START_TIME STOP_TIME NATIVE_START_TIME NATIVE_STOP_TIME PRODUCT_CREATION_TIME |
START_ORBIT_NUMBER STOP_ORBIT_NUMBER MISSION_PHASE_NAME MINIMUM_LATITUDE MAXIMUM_LATITUDE MINIMUM_LONGITUDE MAXIMUM_LONGITUDE POSITIVE_LONGITUDE_DIRECTION SPACECRAFT_NAME INSTRUMENT_ID INSTRUMENT_NAME TARGET_NAME PRODUCER_ID PRODUCER_FULL_NAME PRODUCER_INSTITUTION_NAME DESCRIPTION |
The data set IDs for the EGDR Data Products and required catalog keywords are listed in Section 3.4.
The file naming convention for each EGDR data product produced is xEGnnn_z.TAB, where x shall be replaced with I for the IEGDR or M for the MEGDR, nnn is the bin resolution, e.g. 100 for 1.0 degree bins or 025 for 0.25 degree bins, and z is a letter representing the product version, the first version being A.
The EGDR Data Product is written as an ASCII tabular file with one row per data bin. The table has columns for center latitude, center longitude, mean observed planetary radius, areoid radius, median observed topography, and number of observations in the bin. The file has fixed-length records terminated by carriage return and line feed characters. The EGDR has a detached PDS label in a separate file of the same name, extension .LBL. See Appendix B for an example of a PDS label for an EGDR product.
There shall be one IEGDR Data Product produced from data collected up through the first 90 days of the MGS mapping mission. The IEGDR Data Product will contain 360 x 180 = 64800 bins of data. One line in the table represents one bin. With about 60 characters (bytes) per line, the approximate size of the IEGDR Data Product is therefore 64800 x 60 / 1024000 = 3.8 megabytes. It is expected that this data product will be reprocessed up to 3 times for a total of about 11.4 megabytes over the life of the mission.
The MEGDR Data Product shall be produced from data collected during the entire Mars Global Surveyor mapping mission for a total of one data product. The MEGDR Data Product shall cover a period of 687 days, and shall contain 360 x 4 x 180 x 4 = 1036800 bins of data, making a product size of approximately 60.8 megabytes.
EGDR | Experiment Gridded Data Record |
FTP | File Transfer Protocol |
MEGDR | Mission Experiment Gridded Data Record |
MOLA | Mars Orbiter Laser Altimeter |
PEDR | Precision Experiment Data Record |
PDB | Project Data Base |
PDS | Planetary Data System |
SIS | Software Interface Specification |
SOPC | Science Operations Planning Computer |
PDS_VERSION_ID = PDS3 RECORD_TYPE = FIXED_LENGTH FILE_RECORDS = 64800 RECORD_BYTES = 58 ^TABLE = "IEG100_A.TAB" DATA_SET_ID = "MGS-M-MOLA-5-IEGDR-L3-V1.0" PRODUCT_ID = "MOLA-IEG100_A.TAB" SPACECRAFT_NAME = MARS_GLOBAL_SURVEYOR INSTRUMENT_ID = MOLA INSTRUMENT_NAME = MARS_ORBITER_LASER_ALTIMETER TARGET_NAME = MARS START_TIME = 1997-09-15T19:10:00.000 STOP_TIME = 1999-05-31T23:59:59.999 START_ORBIT_NUMBER = 3 STOP_ORBIT_NUMBER = 11027 PRODUCT_CREATION_TIME = 1999-10-18T20:05:00.000 PRODUCER_ID = MGS_MOLA_TEAM PRODUCER_FULL_NAME = "DAVID E. SMITH" PRODUCER_INSTITUTION_NAME = "GODDARD SPACE FLIGHT CENTER" DESCRIPTION = "This data set is a topographic map of Mars at a resolution of 1 by 1 degree, based on altimetry data acquired by the Mars Global Surveyor MOLA instrument and accumulated over the course of the mission so far. The MOLA Precision Experiment Data Records (PEDRs) are the source for this data set. The map is in the form of an ASCII table with one row for each 1 by 1 degree latitude-longitude bin, from 90 to -90 degrees latitude and from 0 to 360 degrees longitude. The binned data include all MOLA nadir observations from the Orbit Insertion phase, plus Mapping Phase nadir observations from the beginning of mapping through the end of May 1999, plus off-nadir observations of the north pole above 86 degrees latitude acquired during spring 1998. Orbits 355 and 358 of the Orbit Insertion Phase and orbits 10709 through 10716, inclusive, of the Mapping Phase are excluded because solutions for these orbits are deemed to be poor. (Note: subtract 10000 from MOLA mapping phase orbit number to determine the equivalent MGS Project orbit number.) Also excluded are shots more than 1 degree off-nadir (except as noted above), channel 4 returns, and any returns not classified as ground returns, e.g. clouds or noise, according to the SHOT_CLASSIFICATION_CODE. A total of 52,495,550 observations are represented." OBJECT = TABLE INTERCHANGE_FORMAT = ASCII ROWS = 64800 ROW_BYTES = 58 COLUMNS = 6 OBJECT = COLUMN NAME = AREOCENTRIC_LONGITUDE DATA_TYPE = REAL START_BYTE = 1 BYTES = 8 FORMAT = "F8.1" UNIT = DEGREE MINIMUM = 0.5 MAXIMUM = 359.5 DESCRIPTION = "Areocentric east longitude of the center of the 1 by 1 degree area of observation. The rows in the table are in order by increasing longitude (0.5 to 359.5) and decreasing latitude (89.5 to -89.5), with longitude varying first." END_OBJECT = COLUMN OBJECT = COLUMN NAME = AREOCENTRIC_LATITUDE DATA_TYPE = REAL START_BYTE = 9 BYTES = 8 FORMAT = "F8.1" UNIT = DEGREE MINIMUM = -89.5 MAXIMUM = 89.5 DESCRIPTION = "Areocentric latitude of the center of the 1 by 1 degree area of observation. The rows in the table are in order by increasing longitude (0.5 to 359.5) and decreasing latitude (89.5 to -89.5), with longitude varying first." END_OBJECT = COLUMN OBJECT = COLUMN NAME = MEAN_PLANETARY_RADIUS DATA_TYPE = REAL START_BYTE = 17 BYTES = 12 FORMAT = "F12.2" UNIT = METER MINIMUM = 3373396.58 MAXIMUM = 3416455.71 DESCRIPTION = "Mean observed planetary radius within the 1 by 1 degree area. Where no observations lie within the area, an interpolated value is supplied. The mean of the observations is provided as an areodetically useful average, while the median is used for topography." END_OBJECT = COLUMN OBJECT = COLUMN NAME = AREOID_RADIUS DATA_TYPE = REAL START_BYTE = 29 BYTES = 12 FORMAT = "F12.2" UNIT = METER MINIMUM = 3378182.02 MAXIMUM = 3397474.00 DESCRIPTION = "Areoid radius at the center of the 1 by 1 degree area of observation. The areoid radius lies on an equipotential surface whose mean radius at the equator is 3396000 meters. The surface is defined by the Goddard Mars Potential Model MGM0964C20, evaluated to degree and order 50." END_OBJECT = COLUMN OBJECT = COLUMN NAME = MEDIAN_TOPOGRAPHY DATA_TYPE = REAL START_BYTE = 41 BYTES = 10 FORMAT = "F10.2" UNIT = METER MINIMUM = -7501.22 MAXIMUM = 20882.70 DESCRIPTION = "Median observed topography within the 1 by 1 degree area. Where no observations lie within the area, an interpolated value is supplied. The minimum and maximum topography observations within the current data set are -8162.04 and 21223.5. Topography is the planetary radius minus the areoid radius at a longitude and latitude. The areoid radius at the center of the area is not, in general, the same as the mean of the areoid radii at the individual observations. Moreover, the median observed topography follows sharp transitions in height more rapidly than the mean. Thus, the median topography added to the areoid radius is not exactly equal to the mean planetary radius." END_OBJECT = COLUMN OBJECT = COLUMN NAME = OBSERVATIONS DATA_TYPE = INTEGER START_BYTE = 51 BYTES = 6 FORMAT = "I6" MINIMUM = 0 MAXIMUM = 2152 DESCRIPTION = "Number of observations in the 1 by 1 degree area." END_OBJECT = COLUMN END_OBJECT = TABLE END