PDS_VERSION_ID = PDS3 RECORD_TYPE = STREAM RECORD_BYTES = 80 OBJECT = TEXT PUBLICATION_DATE = 2013-03-08 NOTE = "Software Interface Specification for the Spherical Harmonics Binary Data Record (SHBDR) file. Formatted for display or printing at 60 lines per page with up to 78 constant width characters per line." END_OBJECT = TEXT END SOFTWARE INTERFACE SPECIFICATION SPHERICAL HARMONICS BINARY DATA RECORD (SHBDR) prepared by Frank G. Lemoine Code 698, Planetary Geodynamics Laboratory NASA Goddard Space Flight Center Greenbelt, Maryland, 20771 USA Version 1.2 February 20, 2013 |====================================================================| | | | DOCUMENT CHANGE LOG | | | |====================================================================| |REVISION|REVISION| SECTION | REMARKS | | NUMBER | DATE | AFFECTED | | |--------+--------+------------+-------------------------------------| | 1.0 |06/02/20| All |Adapted MGS SHBDR SIS to include | | | | |Mars Reconnaissance Orbiter and | | | | |MESSENGER. |--------+--------+------------+-------------------------------------| | 1.0 |06/03/15| All |Miscellaneous edits | | | | | | |====================================================================| | 1.0 |06/06/29| All |Integration of PDS review comments | |--------+--------+------------+-------------------------------------| | 1.1 |13/02/15| 4.2.2.1 |MRR: Fixed error in column 9, | | | | |"REFERENCE LATITUDE" definition in | | | | |SHBDR_HEADER_TABLE label spec. | | 1.1 | | 4.2.1 |MRR: Changed MESSENGER DATA_SET_ID | | | | | to "MESS-H-RSS/MLA-5-SDP-Vn.m" | |--------+--------+------------+-------------------------------------| | 1.2 |02/20/13| 2.3 | MRR: Changed file naming convention.| | | | Fig. 4-2-1 | | |====================================================================| Contents Document Change Log............................................ii Contents.......................................................iii Acronyms and Abbreviations......................................v 1. General Description..........................................1 1.1. Overview.................................................1 1.2. Scope....................................................1 1.3. Applicable Documents.....................................1 1.4. System Siting............................................2 1.4.1. Interface Location and Medium........................2 1.4.2. Data Sources, Transfer Methods, and Destinations.....2 1.4.3. Generation Method and Frequency......................3 1.5. Assumptions and Constraints..............................3 1.5.1. Usage Constraints....................................3 1.5.2. Priority Phasing Constraints.........................3 1.5.3. Explicit and Derived Constraints.....................3 1.5.4. Documentation Conventions............................3 1.5.4.1. Data Format Descriptions.........................3 1.5.4.2. Time Standards...................................4 1.5.4.3. Coordinate Systems...............................4 1.5.4.4. Limits of This Document..........................4 1.5.4.5. Typographic Conventions..........................4 2. Interface Characteristics....................................5 2.1. Hardware Characteristics and Limitations.................5 2.1.1. Special Equipment and Device Interfaces..............5 2.1.2. Special Setup Requirements...........................5 2.2. Volume and Size..........................................5 2.3. Labeling and Identification..............................5 2.4. Interface Medium Characteristics.........................6 2.5. Failure Protection, Detection, and Recovery Procedures...6 2.6. End-of-File Conventions..................................6 3. Access.......................................................7 3.1. Programs Using the Interface.............................7 3.2. Synchronization Considerations...........................7 3.2.1. Timing and Sequencing Considerations.................7 3.2.2. Effective Duration...................................7 3.2.3. Priority Interrupts..................................7 3.3. Input/Output Protocols, Calling Sequences................7 4. Detailed Interface Specifications............................8 4.1. Structure and Organization Overview......................8 4.2. Detached PDS Label.......................................8 4.2.1. Label Header.........................................8 4.2.2. TABLE Object Definitions............................12 4.2.2.1. SHBDR Header Object Definition....................12 4.2.2.2. SHBDR Names Object Definition.....................14 4.2.2.3. SHBDR Coefficient Object Definition...............14 4.2.2.4 SHBDR Covariance Object Definition................15 4.3. Data File...............................................17 4.3.1. SHBDR Header Object/Block...........................17 4.3.2. SHBDR Name Block....................................18 4.3.3. SHBDR Coefficients Block............................18 4.3.4. SHBDR Covariances Block.............................18 5. Support Staff and Cognizant Personnel.......................19 Appendix A. Description of Spherical Harmonic Model Normalization.20 A.1 Definition of Model for the Potential....................20 A.2 Definition of the normalization used.....................21 Appendix B. Binary Data Format................................22 B.1. IEEE Integer Fields.....................................22 B.2. IEEE Floating-Point Fields..............................22 Appendix C. Example Data Products.............................24 C.1. Example Label...........................................24 C.2. Example Data Object.....................................30 Tables 4-3-1. SHBDR Header Block....................................17 4-3-2. SHBDR Names Block.....................................18 4-3-3. SHBDR Coefficients Block..............................18 4-3-4. SHBDR Covariance Block................................19 Figures 4-2-1. SHBDR Label Header.....................................9 ACRONYMS AND ABBREVIATIONS ANSI American National Standards Institute APL Applied Physics Laboratory ARC Ames Research Center ARCDR Altimetry and Radiometry Composite Data Record ASCII American Standard Code for Information Interchange CCSDS Consultative Committee for Space Data Systems CD-WO Compact-disc write-once CNES Centre National d'Etudes Spatiales CR Carriage Return dB Decibel DSN Deep Space Network DVD Digital Video Disc or Digital Versatile Disc EGM96 Earth Gravitational Model 1996 FEA Front End Assembly GSFC Goddard Space Flight Center IEEE Institute of Electrical and Electronic Engineers IAU International Astronomical Union JHU Johns Hopkins University JPL Jet Propulsion Laboratory J2000 IAU Official Time Epoch K Degrees Kelvin kB Kilobytes km Kilometers LAST Laser Altimeter Science Team (MESSENGER) LF Line Feed LP Lunar Prospector (mission or spacecraft) MB Megabytes MESSENGER MErcury Surface Space ENvironment, GEochemistry, and Ranging (acronym for mission to Mercury) MGN Magellan MGS Mars Global Surveyor MIT Massachusetts Institute of Technology MLA MESSENGER Laser Altimeter MO Mars Observer MRO Mars Reconnaissance Orbiter NAIF Navigation and Ancillary Information Facility NASA National Aeronautics and Space Administration NAV Navigation Subsystem/Team ODL Object Definition Language (PDS) PDB Project Data Base PDS Planetary Data System RST Radio Science Team SCET Space Craft Event Time SFDU Standard Formatted Data Unit SHADR Spherical Harmonics ASCII Data Record SHBDR Spherical Harmonics Binary Data Record SHM Spherical Harmonics Model SIS Software Interface Specification SPARC Sun Scaleable Processor Architecture SPK Spacecraft and Planet Kernel Format, from NAIF TBD To Be Determined UTC Universal Time Coordinated 1. GENERAL DESCRIPTION 1.1. Overview This Software Interface Specification (SIS) describes Spherical Harmonics Binary Data Record (SHBDR) files. The SHBDR is intended to be general and may contain coefficients for spherical harmonic expansions of gravity, topography, magnetic, and other fields. 1.2. Scope The format and content specifications in this SIS apply to all phases of the project for which a SHBDR is produced. The SHBDR was defined initially for gravity models derived from Magellan (MGN and Mars Observer (MO) radio tracking data [1], but the format is more generally useful. The original SHBDR has been adapted for the Mars Global Surveyor (MGS) and the Lunar Prospector (LP) missions; this is the adaptation for the Mars Reconnaissance Orbiter (MRO) and MESSENGER missions. Specifics of the various models are included in [2], which will be updated as data for new spherical harmonic models are incorporated within the SHADR definition. A Spherical Harmonic ASCII Data Record is also defined [3], which may be more suitable when error covariances are not included in the final product. The Jet Propulsion Laboratory (JPL), Pasadena, California, manages the Mars Reconnaissance Orbiter Mission [4], and the Mars Global Surveyor Mission for the National Aeronautics and Space Administration (NASA). The Johns Hopkins University, Laurel, Maryland, USA manages the MESSENGER mission [5,6] for NASA. 1.3. Applicable Documents [1] Tyler, G.L., G. Balmino, D.P. Hinson, W.L. Sjogren, D.E. Smith, R. Woo, S.W. Asmar, M.J. Connally, C.L. Hamilton, and R.A. Simpson, Radio Science Investigations with Mars Observer, J. Geophys. Res., 97, 7759-7779, 1992. [2] Simpson, R.A., Interpretation and Use of Spherical Harmonics ASCII Data Record (SHADR) and Spherical Harmonics Binary Data Record (SHBDR), Version 1.0, 1993. [3] Lemoine, F.G., Software Interface Specification: Spherical Harmonics ASCII Data Record (SHADR), 2006. [4] Mars Reconnaissance Orbiter Mission Plan, Revision C: July 2005, prepared by Robert Lock. Document JPL D-22239, MRO-31-201. [5] McAdams, J. V. (JHU/APL), MESSENGER mission overview and trajectory design, American Institute of Aeronautics and Astronautics, American Astronautical Society (AIAA/AAS) Astrodynamics Specialist Conference, Paper AAS 03-541, 20 pp., Big Sky, MT, August 3-7, 2003. [6] McAdams, J. V., D. W. Dunham, R. W. Farquhar, A. H. Taylor, and B. G. Williams, Trajectory design and maneuver strategy for the MESSENGER mission to Mercury, 15th American Astronautical Society (AAS)/American Institute of Aeronautics and Astronautics (AIAA) Space Flight Mechanics Conference, Paper AAS 05-173, 21 pp., Copper Mountain, CO, Jan. 23-27, 2005. [7] Seidelmann, P.K., V.K. Abalakin, M. Bursa, M. E. Davies, C. de Bergh, J. H. Lieske, J. Oberst, J. L. Simon, E. M. Standish, P. Stooke, P. C. Thomas, Report of the IAU/IAG Working Group on Cartographic Coordinates and Rotational Elements of the Planets and Satellites: 2000, Celes. Mechanics and Dyn. Astronomy, 82, 83-110, Dec 2002. [8] MRO-D-22685, Rev B., Planetary Constants and Models, 05-15-2003. [9] Konopliv, A.S, C.F. Yoder, E. M. Standish, D.-N. Yuan, and W. L. Sjogren, A global solution for the Mars static and seasonal gravity, Mars orientation, Phobos, Deimos Masses, and Mars Ephemeris, Icarus, 182(1), 23-50, 2006. [10] Konopliv A.S., S.W. Asmar, E. Carranza, W.L. Sjogren, and D.N. Yuan, Recent Gravity models as a results of the Lunar Prospector Mission, Icarus, 150, 1-18, 2001. [11] Lambeck, Kurt, Geophysical Geodesy, Oxford University Press, Oxford, UK, 1988. [12] Kaula, William M., Theory of Satellite Geodesy, Applications of satellites to geodesy, Dover Publications, Mineola, NY, 2000. [13] Lemoine, F.G., S.C. Kenyon, J.K. Factor, R.G. Trimmer, N.K. Pavlis, C.M. Cox, S.M. Klosko, S.B. Luthcke, M.H. Torrence, Y.M. Wang, R.G. Williamson, E.C. Pavlis, R.H. Rapp and T.R. Olson, The Development of the Joint NASA GSFC and the National Imagery and Mapping Agency (NIMA) Geopotential Model EGM96, NASA/TP-1998-206861, NASA Goddard Space Flight Center, Greenbelt, Maryland 20771, July 1998. [14] JPL D-7116, Rev. E, Planetary Science Data Dictionary Document, Jet Propulsion Laboratory, Pasadena, California, August 28, 2002. (http://pds.jpl.nasa.gov/documents/psdd/psdd.pdf) [15] JPL D-7669 Part 2, Planetary Data System Standards Reference, PDS Version 3.6, Jet Propulsion Laboratory, August 1, 2003. (http://pds.jpl.nasa.gov/documents/sr/index.html) 1.4. System Siting 1.4.1. Interface Location and Medium SHBDR files are created at the institution conducting the science analysis. SHBDR files can be electronic files or can be stored on compact-disc write-once (CD-WO) or DVD type media. 1.4.2. Data Sources, Transfer Methods, and Destinations SHBDR files are created from radio tracking, vertical sounding, in situ, and/or other measurements at the institution conducting the scientific data analysis. They are transferred to and deposited in a data system (such as the PDS) specified by the managing institution. 1.4.3. Generation Method and Frequency Spherical Harmonic Models are developed separately at each institution conducting scientific analyses on raw data; each model meets criteria specified by the investigators conducting the analysis. Each model requires data with complete sampling (in terms of longitude and latitude coverage on the planet), so that SHBDR files will be issued infrequently and on schedules which cannot be predicted at this time. 1.5. Assumptions and Constraints 1.5.1. Usage Constraints None. 1.5.2. Priority Phasing Constraints None. 1.5.3. Explicit and Derived Constraints None. 1.5.4. Documentation Conventions 1.5.4.1. Data Format Descriptions The reference data unit is the byte. Data may be stored in fields with various sizes and formats, viz. one-, two-, and four-byte binary integers, four- and eight-byte binary floating-point numbers, and character strings. Data are identified throughout this document as char 8 bits character uchar 8 bits integer short 16 bits integer long 32 bits integer float 32 bits floating point (sign, exponent, and mantissa) double 64 bits floating point (sign, exponent, and mantissa) u (prefix) unsigned (as with ulong for unsigned 32-bit integer) other special data structures such as time, date, etc. which are described within this document If a field is described as containing n bytes of ASCII character string data, this implies that the leftmost (lowest numbered) byte contains the first character, the next lowest byte contains the second character, and so forth. An array of n elements is written as array[n]; the first element is array[0], and the last is array[n-1]. Array[n][m] describes an n x m element array, with first element array[0][0], second element array[0][1], and so forth. Floating point (real) numbers are represented as double precision character strings in the FORTRAN 1P1E23.16 format. Fixed point (integer) numbers are represented using the FORTRAN I5 format. 1.5.4.2. Time Standards SHBDR files use the January 1.5, 2000 epoch as the standard time. Within the data files, all times are reported in Universal Coordinated Time (UTC) as strings of 23 ASCII characters. The time format is "YYYY-MM-DDThh:mm:ss.fff", where "-", "T", ":", and "." are fixed delimiters; "YYYY" is the year "19nn" or "20nn"; "MM" is a two- digit month of year; "DD" is a two-digit day of month; "T" separates the date and time segments of the string; "hh" is hour of day; "mm" is the minutes of hour (00-59); "ss" is the seconds of minute (00-59); and "fff" is fractional seconds in milliseconds. The date format is "YYYY-MM-DD", where the components are defined as above. 1.5.4.3. Coordinate Systems The SHBDR uses the appropriate planetocentric fixed body coordinate system [7,8]. This may be an IAU system (e.g. IAU2000 [7] or for the new body-fixed Mars reference frame defined by Konopliv et al. [9]. At present, the MESSENGER mission has adopted the IAU2000 model for Mercury [7]. The coordinate system for lunar geopotential models will be a body figure axis system defined by the lunar librations, which are resolved by lunar laser ranging [10], or a coarser frame defined by the IAU [7]. 1.5.4.4. Limits of This Document This document applies only to SHBDR data files. 1.5.4.5. Typographic Conventions This document has been formatted for simple electronic file transfer and display. Line lengths are limited to approximately 80 ASCII characters, including line delimiters. No special fonts or structures are included within the file. Constant width characters are assumed for display. 2. INTERFACE CHARACTERISTICS 2.1. Hardware Characteristics and Limitations 2.1.1. Special Equipment and Device Interfaces Users of the SHBDR product must have access to the data system (or to media) on which SHBDR files are stored. 2.1.2. Special Setup Requirements None. 2.2. Volume and Size SHBDR products have variable length, depending on the degree and order of the model and the number of tables included. A model of degree and order N will include approximately N**2 terms and therefore the number of terms in the covariance matrix will be of order N**4. For 8-byte storage and N=50, the total SHBDR volume will be about 30 MB. For N=100, the total SHBDR volume will be approximately 416 MB. Vector quantities (e.g., magnetic field) may be described by a single SHBDR (in which all components are represented) or by a separate SHBDR for each field component. If the single SHBDR includes covariances, the file size will be approximately 27 times larger than the combined volumes of the three component files because of the inter-component covariance terms. In general, the SHBDR is recommended over the SHADR [3] when the data include error covariances because of the smaller data volume associated with binary formats. 2.3. Labeling and Identification Each file has a name which describes its contents. The name includes the following structure which uniquely identifies it among SHBDR products: GTmmm_ddVnn_SHB.DAT where "G" denotes the generating institution "J" for the Jet Propulsion Laboratory "G" or Goddard Space Flight Center "C" or Centre National d'Etudes Spatiales "M" for Massachusetts Institute of Technology "T" indicates the type of data represented "G" for gravity field "T" for topography "M" for magnetic field "mmm" indicates the mission "MES" for MESSENGER "dd" indicates the degree and order of the model (e.g., 20). "SHB" denotes that this is a Binary file of Spherical Harmonic coefficients and error covariance information "DAT" denotes that this is a binary data file Each SHBDR file is accompanied by a detached PDS label; that label is a file in its own right, having the name GTmmm_ddVnn_SHB.LBL. 2.4. Interface Medium Characteristics SHBDR products are electronic files. 2.5. Failure Protection, Detection, and Recovery Procedures None. 2.6. End-of-File Conventions End of file labeling complies with standards for the medium on which the files are stored. 3. ACCESS 3.1. Programs Using the Interface Data contained in SHBDR files will be accessed by programs at the home institutions of science investigators. Those programs cannot be identified here. 3.2. Synchronization Considerations 3.2.1. Timing and Sequencing Considerations N/A 3.2.2. Effective Duration N/A 3.2.3. Priority Interrupts None. 3.3. Input/Output Protocols, Calling Sequences None. 4. DETAILED INTERFACE SPECIFICATIONS 4.1. Structure and Organization Overview The SHBDR is a file generated by software at the institution conducting scientific data analysis. Each SHBDR file is accompanied by a detached PDS label. 4.2. Detached PDS Label The detached PDS label is a file with two parts -- a header, and a set of one to four PDS TABLE object definitions. The header contains information about the origin of the file and its general characteristics such as record type and size. The TABLE object definitions describe the format and content of the tables that make up the SHBDR data file. The SHBDR Header Table Object definition is required. The SHBDR Names Object Definition is required if there is an SHBDR Names Object in the file. The SHBDR Coefficients Table Object definition is required if there is a SHBDR Coefficients Table in the file; the SHBDR Covariance Table Object definition is required if there is a SHBDR Covariance Table. Each detached PDS label is constructed of ASCII records; each record in the label contains exactly 80 characters. The last two characters in each record are the carriage-return (ASCII 13) and line-feed (ASCII 10) characters. An example of a complete label and data object is given in Appendix C. 4.2.1 Label Header The structure of the label header is illustrated in Figure 4-2-1. Keyword definitions are given below. PDS_VERSION_ID = The version of the Planetary Data System for which these data have been prepared; set to PDS3 by agreement between the mission and PDS. RECORD_TYPE = The type of record. Set to "FIXED_LENGTH" to indicate that all logical records have the same length. RECORD_BYTES = The number of bytes per (fixed-length) record. FILE_RECORDS = The number of records in the SHBDR file: instance dependent. ^SHBDR_HEADER_TABLE= File name and record number at which SHBDR_HEADER_TABLE begins. Set to ("GTnnnnvv.SHA",1) where "GTnnnnvv.SHB" is the file name as described in Section 2.3, and 1 is the record number since this is the first record in the SHBDR file. |====================================================================| | | | Figure 4-2-1 SHBDR Label Header | | | |====================================================================| | | | PDS_VERSION_ID = PDS3 | RECORD_TYPE = FIXED_LENGTH | | RECORD_BYTES = nnn | | FILE_RECORDS = nnn | | ^SHBDR_HEADER_TABLE = ("GTmmm_ddVnn_SHB.DAT",1) | | ^SHBDR_NAMES_TABLE = ("GTmmm_ddVnn_SHB.DAT",1) | | ^SHBDR_COEFFICIENTS_TABLE = ("GTmmm_ddVnn_SHB.DAT",nn) | | ^SHBDR_COVARIANCE_TABLE = ("GTmmm_ddVnn_SHB.DAT",nnn) | | INSTRUMENT_HOST_NAME = "cccccccccccccccccccc" | | TARGET_NAME = "cccc" | | INSTRUMENT_NAME = "ccccccccccccccccccccccc" | | DATA_SET_ID = "ccccccccccccccccccccccc" | | OBSERVATION_TYPE = "ccccccccccccc" | | ORIGINAL_PRODUCT_ID = "ccccccccccccc" | | PRODUCT_ID = "GTmmm_ddVnn_SHB" | | PRODUCT_RELEASE_DATE = YYYY-MM-DD | | DESCRIPTION = "cccccccccccccccccc" | | START_ORBIT_NUMBER = nnnn | | STOP_ORBIT_NUMBER = nnnn | | START_TIME = YYYY-MM-DDThh:mm:ss | | STOP_TIME = YYYY-MM-DDThh:mm:ss | | PRODUCT_CREATION_TIME = YYYY-MM-DDThh:mm:ss.fff | | PRODUCER_FULL_NAME = "cccccccccccc" | | PRODUCER_INSTITUTION_NAME = "ccccccccccc" | | PRODUCT_VERSION_TYPE = "cccccccccccc" | | PRODUCER_ID = "ccccccc" | | SOFTWARE_NAME = "ccccccc;Vn.m" | |====================================================================| ^SHBDR_NAMES_TABLE = File name and record number at which the SHBDR_NAMES_TABLE begins. The Names Table is required if the Coefficients Table is included in the file. This pointer will not appear in the SHBDR label if there are no Coefficients Table. Set to ("GTmmm_ddVnn_SHB.DAT",nn) where "GTmmm_ddVnn_SHB.DAT" is the file name as described in Section 2.3, and "nn" is the record number in the file where the Names Table begins. ^SHBDR_COEFFICIENTS_TABLE= File name and record number at which SHBDR_COEFFICIENTS_TABLE begins. The Coefficients Table is optional; this pointer will not appear in the SHBDR label if there is no Coefficients Table. Set to ("GTmmm_ddVnn_SHB.DAT",nn) where "GTmmm_ddVnn_SHB.DAT" is the file name as described in Section 2.3, and "nn" is the record number in the file where the Coefficients Table begins. ^SHBDR_COVARIANCE_TABLE= File name and record number at which SHBDR_COVARIANCE_TABLE begins. The Covariance Table is optional; this pointer will not appear in the SHBDR label if there is no Covariance Table. Set to ("GTmmm_ddVnn_SHB.DAT",nn) where "GTmmm_ddVnn_SHB.DAT" is the file name as described in Section 2.3, and "nn" is the record number in the file where the Covariance Table begins. INSTRUMENT_HOST_NAME = Name of the spacecraft; acceptable names include "MARS GLOBAL SURVEYOR" "LUNAR PROSPECTOR", "MARS RECONNAISSANCE ORBITER", and "MERCURY SURFACE, SPACE, ENVIRONMENT, GEOCHEMISTRY, AND RANGING". TARGET_NAME = A character string that identifies the target body. For MRO- and MGS- derived SHBDR files, the character string will be "MARS". For MESSENGER SHBDR files the character string will be "MERCURY". For Lunar Prospector SHBDR files, the character string will be "MOON". INSTRUMENT_NAME = Name of the instrument; set to "RADIO SCIENCE SUBSYSTEM" for products generated from radio science data, or set to other instrument names as appropriate. DATA_SET_ID = Identifier for the data set of which this SHBDR product is a member. -Set to "MRO-M-RSS-5-SDP-Vn.m" for Mars Reconnaissance Orbiter; -Set to "MESS-H-RSS/MLA-5-SDP-Vn.m" for MESSENGER; -Set to "MGS-M-RSS-5-SDP-Vn.m" for MGS; and " -Set to "LP-L-RSS-5-SHGBDR-L2-Vn.m" for Lunar Prospector; The suffix Vn.m indicates the version number of the data set. OBSERVATION_TYPE = A character string that identifies the data in the product. For the spherical harmonic model of a gravity field, the character string "GRAVITY FIELD". For a model of planet topography, the character string "TOPOGRAPHY". ORIGINAL_PRODUCT_ID = Optional. An identifier for the product provided by the producer. Generally a file name, different from PRODUCT_ID, which would be recognized at the producer's home institution. PRODUCT_ID = A unique identifier for the product within the collection identified by DATA_SET_ID. Generally, the file name used in pointers ^SHBDR_HEADER_TABLE. The naming convention is defined in Section 2.3. PRODUCT_RELEASE_DATE = The date on which the product was released to the Planetary Data System; entered in the format "YYYY-MM-DD", where components are defined in Section 1.5.4.2. DESCRIPTION = A short description of the SHBDR product. START_ORBIT_NUMBER = Optional. The first orbit represented in the SHBDR product. An integer. STOP_ORBIT_NUMBER = Optional. The last orbit represented in the SHBDR product. An integer. START_TIME = Optional. The date/time of the first data included in the model, expressed in the format "YYYY-MM-DDThh:mm:ss" where the components are defined in section 1.5.4.2. STOP_TIME = Optional. The date/time of the last data included in the model, expressed in the format "YYYY-MM-DDThh:mm:ss" where the components are defined in section 1.5.4.2. PRODUCT_CREATION_TIME = The time at which this SHBDR was created; expressed in the format "YYYY-MM- DDThh:mm:ss.fff" where the components are defined in Section 1.5.4.2. PRODUCER_FULL_NAME= The name of the person primarily responsible for production of this SHBDR file. Expressed as a character string, for example "JOHANNES KEPLER". PRODUCER_INSTITUTION_NAME= The name of the institution primarily responsible for production of this SHADR. Standard values include: "STANFORD UNIVERSITY" "GODDARD SPACE FLIGHT CENTER" "JET PROPULSION LABORATORY" "CENTRE NATIONAL D'ETUDES SPATIALES" "MASSACHUSETTS INSTITUTE OF TECHNOLOGY" PRODUCT_VERSION_TYPE= The version of this SHBDR. Standard values include "PREDICT", "PRELIMINARY", and "FINAL". PRODUCER_ID = The entity responsible for creation of the SHBDR product. For products generated by the Mars Reconnaissance Orbiter Gravity Science Team set to "MRO GST". For products generated by the MESSENGER Laser Altimeter Science Team, set to "MESS LAST". For products generated by the Mars Global Surveyor Radio Science Team, set to "MGS RST". SOFTWARE_NAME = The name and version number of the program creating this SHBDR file; expressed as a character string in the format "PROGRAM_NAME;n.mm" where "PROGRAM_NAME" is the name of the software and "n.mm" is the version number. (e.g. "SOLVE;200201.02") 4.2.2 TABLE Object Definitions 4.2.2.1 SHBDR Header Object Definition Each SHBDR Header Object is completely defined by the Header Object Definition in its Label. The definition which follows gives the structure of the Header Object; some of the DESCRIPTION values may vary from product to product. The SHBDR Header Object Definition is a required part of the SHBDR label file. It immediately follows OBJECT = SHBDR_HEADER_TABLE ROWS = 1 COLUMNS = 9 ROW_BYTES = 56 INTERCHANGE_FORMAT = BINARY DESCRIPTION = "The SHBDR header includes descriptive information about the spherical harmonic coefficients that follow in SHBDR_COEFFICIENTS_TABLE. The header consists of a single record of nine data columns requiring 56 bytes. The Header is followed by a pad of binary integer zeroes to ensure alignment with RECORD_BYTES." OBJECT = COLUMN NAME = "REFERENCE RADIUS" DATA_TYPE = IEEE_REAL START_BYTE = 1 BYTES = 8 UNIT = "KILOMETER" DESCRIPTION = "The assumed reference radius of the spherical planet." END_OBJECT = COLUMN OBJECT = COLUMN NAME = "CONSTANT" DATA_TYPE = IEEE_REAL START_BYTE = 9 BYTES = 8 UNIT = "N/A" DESCRIPTION = "For a gravity field model the assumed gravitational constant GM in kilometers cubed per seconds squared for the planet. For a topography model, set to 1." END_OBJECT = COLUMN OBJECT = COLUMN NAME = "UNCERTAINTY IN CONSTANT" DATA_TYPE = IEEE_REAL START_BYTE = 17 BYTES = 8 UNIT = "N/A" DESCRIPTION = "For a gravity field model the uncertainty in the gravitational constant GM in kilometers cubed per seconds squared for the planet. For a topography, set to 0." END_OBJECT = COLUMN OBJECT = COLUMN NAME = "DEGREE OF FIELD" DATA_TYPE = MSB_INTEGER START_BYTE = 25 BYTES = 4 UNIT = "N/A" DESCRIPTION = "The degree of model field." END_OBJECT = COLUMN OBJECT = COLUMN NAME = "ORDER OF FIELD" DATA_TYPE = MSB_INTEGER START_BYTE = 29 BYTES = 4 UNIT = "N/A" DESCRIPTION = "The order of the model field." END_OBJECT = COLUMN OBJECT = COLUMN NAME = "NORMALIZATION STATE" DATA_TYPE = MSB_INTEGER START_BYTE = 33 BYTES = 4 UNIT = "N/A" DESCRIPTION = "The normalization indicator. For gravity field: 0 coefficients are unnormalized 1 coefficients are normalized 2 other." END_OBJECT= COLUMN OBJECT = COLUMN NAME = "NUMBER OF NAMES" DATA_TYPE = MSB_INTEGER START_BYTE = 37 BYTES = 4 UNIT = "N/A" DESCRIPTION = "Number of valid names in the SHBDR Names Table. Also, the number of valid coefficients in the SHBDR Coefficients Table." END_OBJECT = COLUMN OBJECT = COLUMN NAME = "REFERENCE LONGITUDE" POSITIVE_LONGITUDE_DIRECTION = "EAST" DATA_TYPE = IEEE_REAL START_BYTE = 41 BYTES = 8 UNIT = "DEGREE" DESCRIPTION = "The reference longitude for the spherical harmonic expansion; normally 0." END_OBJECT = COLUMN OBJECT = COLUMN NAME = "REFERENCE LATITUDE" DATA_TYPE = IEEE_REAL START_BYTE = 49 BYTES = 8 UNIT = "DEGREE" DESCRIPTION = "The reference latitude for the spherical harmonic expansion; normally 0." END_OBJECT = COLUMN END_OBJECT = SHBDR_HEADER_TABLE 4.2.2.2 SHBDR Names Object Definition The SHBDR Names Object is completely defined by the Names Object Definition in the label. The definition below illustrates general structural form. The SHBDR Names Object is an optional part of the SHBDR file. If the Names Object is not included, either the Names Object Definition will be omitted or the number of rows will be set to zero (ROWS = 0). If the Names Object is not included, the pointer ^SHBDR_NAMES_TABLE will not appear in the Standard Keywords and Values. If the Coefficients Object is included in the SHBDR file, the Names Object is required. OBJECT = SHADR_NAMES_TABLE ROWS = * COLUMNS = 1 ROW_BYTES = 8 INTERCHANGE_FORMAT = BINARY DESCRIPTION = "The SHBDR Names Table contains names for the solution parameters (including gravity field coefficients) which will follow in the SHBDR_COEFFICIENTS_TABLE. The order of the names in the SHBDR_NAMES_TABLE corresponds identically to the order of the parameters in the SHBDR_COEFFICIENTS_TABLE. Each coefficient name is of the form Cnm or Snm where n is the degree of the coefficient and m is the order of the coefficient. Both indices are three-digit zero-filled right-justified ASCII character strings (for example, C010005 for the 10th degree 5th order C coefficient, or S002001 for the 2nd degree 1st order S coefficient). The eighth byte in the table is an ASCII blank used to ensure that the row length is equal to RECORD_BYTES. Names of other solution parameters are limited to 8 ASCII characters; if less than 8, they will be left-justified and padded with ASCII blanks. The Names Table itself will be padded with ASCII blanks, if necessary, so that its length is an integral multiple of RECORD_BYTES." OBJECT = COLUMN NAME = "PARAMETER NAME" DATA_TYPE = CHARACTER START_BYTE = 1 BYTES = 8 UNIT = "N/A" DESCRIPTION = "The name of the coefficient or other solution parameter, left-justified and padded with ASCII blanks (if needed) to 8 characters." END_OBJECT = COLUMN END_OBJECT = SHBDR_NAMES_TABLE 4.2.2.3 SHBDR Coefficients Object Definition The SHBDR Coefficients Object is completely defined by the Coefficients Object Definition in the label. Small differences in DESCRIPTION values should be expected from product to product. The structure outlined in the Definition below should not vary, however. The SHBDR Coefficients Object is an optional part of the SHBDR data file. This allows the SHBDR to be used for targets which are too small or too remote to have easily discerned coefficients, but for which estimates of mass have been obtained (e.g., satellites Phobos and Deimos). If the Covariance Object is included in the SHBDR, the Coefficients Object is required. If the Coefficients Object is not included in the SHBDR file, either the SHBDR Coefficients Object Definition will be omitted or the number of rows will be set to zero (ROWS = 0). If the SHBDR Coefficients Object is not included, the pointer ^SHBDR_COEFFICIENTS_TABLE will not appear in the label header. If the SHBDR Coefficients Object Definition is included in the label, it immediately follows the SHBDR Names Object Definition. The order in which coefficients appear in the Coefficients Object is defined by the Names Object [2]. OBJECT = SHBDR_COEFFICIENTS_TABLE ROWS = * COLUMNS = 1 ROW_BYTES = 8 INTERCHANGE_FORMAT = BINARY DESCRIPTION = "The SHBDR Coefficients Table contains the coefficients and other solution parameters for the spherical harmonic model. The order of the coefficients in this table corresponds exactly to the order of the coefficient and parameter names in SHBDR_NAMES_TABLE. The SHBDR Coefficients Table will be padded with double precision DATA_TYPE zeroes so that its total length is an integral multiple of RECORD_BYTES." OBJECT = COLUMN NAME = "COEFFICIENT VALUE" DATA_TYPE = * START_BYTE = 1 BYTES = 8 UNIT = "N/A" DESCRIPTION = "A coefficient Cnm or Snm or other solution parameter as specified in the SHBDR Names Table." END_OBJECT = COLUMN END_OBJECT = SHBDR_COEFFICIENTS_TABLE 4.2.2.4 SHBDR Covariance Object Definition The SHBDR Covariance Object is completely defined by the Covariance Object Definition in the label. Small differences in DESCRIPTION values should be expected from product to product. The structure established by the Definition below should not change, however. The SHBDR Covariance Object is an optional part of the SHBDR data file. If the Covariance Object is not included, either the Covariance Object Definition will be omitted or the number of rows will be set to zero (ROWS = 0). If the SHBDR Covariance Object is not included, the pointer ^SHBDR_COVARIANCE_TABLE will not appear in the label header. If the SHBDR Covariance Object Definition is included in the label, it immediately follows the SHBDR Coefficients Object Definition. The order in which covariance terms appear in the Covariance Object is defined by the Names Object [2]. OBJECT = SHBDR_COVARIANCE_TABLE ROWS = * COLUMNS = 1 ROW_BYTES = 8 INTERCHANGE_FORMAT = BINARY DESCRIPTION = "The SHBDR Covariance Table contains the covariances for the spherical harmonic model coefficients and other solution parameters. The order of the covariances in this table is defined by the product of the SHBDR Names Table with its transpose, except that redundant terms are omitted on their second occurrence. The SHBDR Covariance Table will be padded with double precision DATA_TYPE zeroes so that its total length is an integral multiple of RECORD_BYTES." OBJECT = COLUMN NAME = "COVARIANCE VALUE" DATA_TYPE = * START_BYTE = 1 BYTES = 8 UNIT = "N/A" DESCRIPTION = "The covariance value for the coefficients and other solution parameters specified by the product of SHBDR_NAMES_TABLE with its transpose, after omitting redundant terms." END_OBJECT = COLUMN END_OBJECT = SHBDR_COVARIANCE_TABLE 4.3. Data File Each SHBDR data file comprises one or more data blocks. The data objects were defined in Section 4.2. The data blocks are illustrated below. The Header Object is required in each SHBDR file; the Names Object, the Coefficients Object, and the Covariance Object are optional. If the Covariance Object is included, both the Coefficients Object and the Names Object are required; if the Coefficients Object is included, the Names Object is required. 4.3.1. SHBDR Header Object/Block The SHBDR Header Object contains the parameters necessary to interpret the data in the SHBDR file. The structure and content of the SHBDR Header Object are defined in Section 4.2.2.1. The SHBDR Header Object is a one-row table; hence the Header Object and the Header Block are logically synonymous. The structure of the Header Block is shown in Table 4-3-1. |====================================================================| | | | Table 4-3-1. SHBDR Header Block | | | |====================================================================| | Col No | Offset | Length | Format | Column Name | |--------|--------|--------|--------|--------------------------------| | 1 | +0 | 8 | double |Planetary Radius | |--------|--------|--------|--------|--------------------------------| | 2 | 8 | 8 | double |Constant | |--------|--------|--------|--------|--------------------------------| | 3 | 16 | 8 | double |Uncertainty in Constant | |--------|--------|--------|--------|--------------------------------| | 4 | 24 | 4 | long |Degree of Field | |--------|--------|--------|--------|--------------------------------| | 5 | 28 | 4 | long |Order of Field | |--------|--------|--------|--------|--------------------------------| | 6 | 32 | 4 | long |Normalization State | |--------|--------|--------|--------|--------------------------------| | 7 | 36 | 4 | long |Number of Names | |--------|--------|--------|--------|--------------------------------| | 8 | 40 | 8 | double |Reference Longitude | |--------|--------|--------|--------|--------------------------------| | 9 | 48 | 8 | double |Reference Latitude | |--------|--------|--------|--------|--------------------------------| | | +56 | | |========|========|========|========|================================| 4.3.2. SHBDR Names Block The SHBDR Names Object comprises one or more SHBDR Names Blocks. Each block contains the name of one coefficient or solution parameter in the Spherical Harmonic Model. The structure and content of the SHBDR Names Object are defined in Section 4.2.2.2. The structure of an individual block is shown in Table 4-3-2. |====================================================================| | | | Table 4-3-2. SHBDR Names Block | | | |====================================================================| | Col No | Offset | Length | Format | Column Name | |--------|--------|--------|--------|--------------------------------| | 1 | +0 | 8 | A8 |Coefficient or Solution | | | | | |Parameter Name | |--------|--------|--------|--------|--------------------------------| | | +8 | | |========|========|========|========|================================| 4.3.3. SHBDR Coefficients Block The SHBDR Coefficients Object comprises one or more SHBDR Coefficients Blocks. Each block contains the value of one coefficient or other solution parameter for the overall model defined by the SHBDR product. The structure and content of the SHBDR Coefficients Object are defined in Section 4.2.2.3. The structure of an individual block is shown in Table 4-3-3. |====================================================================| | | | Table 4-3-3. SHBDR Coefficients Block | | | |====================================================================| | Col No | Offset | Length | Format | Column Name | |--------|--------|--------|--------|--------------------------------| | 1 | +0 | 8 | double |Coefficient Cnm or Snm or | | | | | |other solution parameter | |--------|--------|--------|--------|--------------------------------| | | +8 | | |========|========|========|========|================================| 4.3.4. SHBDR Covariance Block The SHBDR Covariance Object comprises one or more SHBDR Covariance Blocks. Each SHBDR Covariance Block contains one covariance for the overall model defined by the SHBDR product. The structure and content of the SHBDR Covariance Object are defined in Section 4.2.2.4. The structure of an individual block is shown in Table 4-3-4. The SHBDR Covariance Object is an optional component of the SHBDR file. |====================================================================| | | | Table 4-3-4. SHBDR Covariance Block | | | |====================================================================| | Col No | Offset | Length | Format | Column Name | |--------|--------|--------|--------|--------------------------------| | 1 | +0 | 8 | double |Covariance Value | |--------|--------|--------|--------|--------------------------------| | | +8 | | |========|========|========|========|================================| 5. SUPPORT STAFF AND COGNIZANT PERSONNEL The following persons may be contacted for information. Mars Reconnaissance Orbiter Gravity Science Team Frank G. Lemoine Code 698, Planetary Geodynamics Laboratory NASA Goddard Space Flight Center Greenbelt, Maryland 20771 U.S.A. Phone: 301-614-6109 FAX: 301-614-6522 Electronic mail: Frank.Lemoine@gsfc.nasa.gov MESSENGER Laser Altimeter Science Team Maria T. Zuber Department of Earth, Atmospheric, and Planetary Sciences Massachusetts Institute of Technology 54-918 Cambridge, MA 02139-4307 Phone: 617-253-0149 FAX: 617-253-8298 Planetary Data System: PDS Operator Planetary Data System MS 202-101 Jet Propulsion Laboratory 4800 Oak Grove Drive Pasadena, CA 91109-8099 Phone: 818-354-4321 Electronic Mail: pds_operator@jpl.nasa.gov APPENDIX A. A.1 DEFINITION OF SPHERICAL HARMONIC MODELS FOR THE GEOPOTENTIAL. Spherical harmonics satisfy Laplace's equation in spherical coordinates. The gravity potential field of the planets and the mathematical representation of magnetic fields and topographic fields are readily expressed in terms of spherical harmonics. Useful reviews are by Lambeck [11] (Section 2.2, Elements of Potential Theory) and Kaula [12] (Section 1.1 Potential Theory, and Section 1.2 Spherical Harmonics). V = (GM/r) + (GM/r)*SUMMATION_n SUMMATION_m (Re/r)**n [Cnm" cos(mL) + Snm" sin(mL)]* Pnm"(sin(phi)) (Equation A-1-1) where GM is the gravitational constant of the planet, r is the radial distance of the test point from the origin, and Re is the assumed reference radius of the spherical planet for which the coefficients were calculated. The summations take place from degree n=1 to infinity, and order m=0 to n; Cnm" and Snm" refer to the normalized spherical harmonic coefficients (see Section A.2 below); L is the longitude; the Pnm" are the normalized associated Legendre functions of degree n and order m; and phi is the latitude of the test point. If we assume the origin is at the center of mass, the degree one terms vanish, and the summation in degree starts at degree n=2. A "solution" for a spherical harmonic model of the geopotential refers to a solution for these spherical harmonic coefficients and the gravitational constant, GM, of the body. In practice the spherical harmonic series is truncated at a maximum degree nmax. For MRO, the likely degree of truncation will be between n=100 and n=120. For MESSENGER gravity solutions of the planet Mercury, solutions will likely be truncated at degree 20. The degree of truncation depends on the quality of the tracking data, and the orbits of the spacecraft in the geopotential solution. For Lunar Prospector derived gravity solutions, the maximum degree has ranged from n=100 to n=165 [10]. If the origin is placed at the center of mass, the degree 1 terms vanish from the spherical harmonic expansion, and the first summation above is then from (n=2) to the maximum degree, nmax. Figure 1, section 1.2 from Kaula [11] gives examples of spherical harmonics. The zonal terms, m=0, have n zeros in a distance pi along a meridian N-S in other words they represent only latitudinal varations in the potential. Zonal terms may be represented in the literature as Jn = - Cn0. Aside from GM, C20 is the most significant term in the gravity field (for planets such as the Earth and Mars), and reflects the dynamical expression of the planet's polar flattening. Tesseral harmonics (coefficients where n is not equal to m, and m > 0, have n-m zeros in a distance pi along a meridian (like the tesserae of a mosaic). Sectoral harmonics are coefficients where n=m and are constant in sectors of longitude (N-S) and have n zero crossings in a distance pi along a meridian of latitude (E-W). A.2 DEFINITION OF THE NORMALIZATION USED FOR GEOPOTENTIAL COEFFICIENTS. The normalization for spherical harmonic coefficients is given by Lambeck[11] Cnm" = Cnm/PI_nm (Equation A-2-1) where Cnm" is normalized and Cnm is un-normalized, and [PI_nm]**2 = (2 - delta_0m) * (2n+1) * (n-m)! / (n+m)! (Equation A-2-2) delta_0m refers to the Kronecker delta function -- unity for coefficients where m=0 (the zonal terms), zero for order m > 0. For zonal coefficients (m=0) the relation reduces to Cnm" = Cnm / sqrt(2n+1) For example, for the Earth C20 = -1.08262668355E-03 (un-normalized) so C20" = C20 / sqrt(5) = -4.8416537173572E-04 (normalized) Working the process backwards for Earth's C22 we have C22" = .24391435239839D-05 (from the Earth Gravitational Model 1996, EGM96, [13]) [PI_nm]**2 = (2-0)*(2n+1) (2-2)! / (4)! = 2*5*1/(4!) = 5/12 which yields C22 = sqrt(5/12) * (.24391435239839E-05) = 1.5744604E-06 closely matching Lambeck's [11] result (page 14). Likewise for Earth's S22, we have S22" = -.14001668365394E-05 (normalized from the Earth Gravitational Model 1996, EGM96, [13]) Thus, S22= sqrt(5/12) * (-.14001668365394E-05) = -9.038038E-07 (un-normalized) which matches closely the example given by Lambeck [11]. APPENDIX B. BINARY DATA FORMAT B.1. IEEE INTEGER FIELDS 0 7 1-byte (char; uchar) --------- | [0] | --------- 0 15 2-byte (short; ushort) --------- --------- | [0] | [1] | --------- --------- 0 31 4-byte (long; ulong) --------- --------- --------- --------- | [0] | [1] | [2] | [3] | --------- --------- --------- --------- IEEE binary integers are stored in one, two, or four consecutive 8-bit bytes. Unsigned integers uchar, ushort, ulong, which always represent positive values, contain 8, 16, or 32 binary bits, respectively. As illustrated above, the significance increases from the rightmost bit to the leftmost (bit 0). Signed integers (char, short, long) are stored in the same way, except that negative values are formed by taking the corresponding positive value, complementing each bit, then adding unity -- known as "two's complement" format. As a consequence, a negative value always has bit 0 set "on". Integers are written externally in increasing byte-number order, i.e. [0], [1], etc., so that more significant bits always precede less significant ones. For example, the short value -2 is stored as a pair of bytes valued 0xff, 0xfe. B.2. IEEE Floating-Point Fields 0 1 8 9 31 4-byte (float) --------- --------- --------- --------- | | [0] | | [1] | [2] | [3] | --------- --------- --------- --------- 0 1 8 9 31 8-byte (double) --------- --------- --------- --------- | | [0] | | [1] | [2] | [3] | --------- --------- --------- --------- 32 63 --------- --------- --------- --------- | [4] | [5] | [6] | [7] | --------- --------- --------- --------- IEEE single- (double-) precision floating point numbers (known to IEEE enthusiasts as E-type floating-point formats, respectively) are stored in four (eight) consecutive bytes. Bit number 0 contains a sign indicator, S. Bits 1 through 8 (11) contain a binary exponent, E. The significance increases from bit 8 (11) through bit 1. Bits 9 (12) through 31 (63) contain a mantissa M, a 23-bit (52-bit) binary fraction whose binary point lies immediately to the left of bit 9 (12). The significance increases from bit 31 (63) through bit 9 (11). The value of the single-precision field is given by S E-127 (-1) *2 *(1+M) The value of the double-precision field is given by S E-1023 (-1) *2 *(1+M) The numbers are stored externally in increasing byte-number order, i.e. [0], [1], etc. For example, the maximum single-precision float value +3.40282347E+38 is stored as four bytes valued 0x7f, 0x7f, 0xff, 0xff. Special single-precision float values are represented as +Infinity (0x7f800000), -Infinity (0xff800000), quiet NaN (not a number) (0xffffffff), and signaling NaN (0x7f800001). APPENDIX C EXAMPLE DATA PRODUCTS APPENDIX C.1 EXAMPLE LABEL The following lists an example SHBDR LBL file for a Mars gravity solution, GGM2BC80.SHB, prepared by Frank Lemoine of NASA GSFC. For MESSENGER the "INSTRUMENT_HOST_NAME" would be listed instead of "MESSENGER" instead of "MARS RECONNAISSANCE ORBITER". The DESCRIPTION would be changed to reflect the data content of the MESSENGER gravity solutions. Other fields (e.g., PRODUCT_RELEASE_DATE, PRODUCT_ID, INSTRUMENT NAME, START_TIME, STOP_TIME, PRODUCT_CREATION TIME) would also be changed as appropriate. PDS_VERSION_ID = "PDS3" FILE_NAME = "GGM2BC80.SHB" RECORD_TYPE = FIXED_LENGTH RECORD_BYTES = 512 FILE_RECORDS = 336254 ^SHBDR_HEADER_TABLE = ("GGM2BC80.SHB",1) ^SHBDR_NAMES_TABLE = ("GGM2BC80.SHB",2) ^SHBDR_COEFFICIENTS_TABLE = ("GGM2BC80.SHB",105) ^SHBDR_COVARIANCE_TABLE = ("GGM2BC80.SHB",208) INSTRUMENT_HOST_NAME = "MARS RECONNAISSANCE ORBITER" TARGET_NAME = "MARS" INSTRUMENT_NAME = "RADIO SCIENCE SUBSYSTEM" DATA_SET_ID = "MRO-M-RSS-5-SDP-V1.0" OBSERVATION_TYPE = "GRAVITY FIELD" PRODUCT_ID = "GGM2BC80.SHB" PRODUCT_RELEASE_DATE = 2006-02-28 DESCRIPTION = " The data in this covariance matrix are stored row-wise, in upper triangular form. The error covariance contains 21506961 elements and has 336254 records. There are 6558 parameters in the GGM2BC80.SHB covariance matrix: the C and S gravity coefficients from degree 2 to 80 (inclusive) and the GM of the Mars gravity field. The data format is big endian. This file contains coefficients and related data for a spherical harmonic model of the Mars gravity field. Input data are from radio tracking of the Mars Global Surveyor spacecraft; no Mariner 9 or Viking data are included. Coordinate system is IAU 1991 (Davies et al., Celestial Mechanics and Dynamical Astronomy, 53, 377-397, 1992). The model was constructed from 955,115 observations, summarized in the table below. MGS data are limited to tracking from the Aerobraking Hiatus and Science Phasing Orbit (SPO) subphases of the Orbit Insertion phase of the mission and to February 1999 to February 2000 after the orbit was circularized. Time Periods Total Arcs Observations ----------------------- ---- ------------ Hiatus 2 24119 SPO-1 8 31001 SPO-2 16 157972 Feb-Mar 1999 9 76813 Apr 1999 - Feb 2000 47 665210 ----------------------- ---- ------------ Total 955115 Orbit reconstruction was improved using Mars Orbiter Laser Altimeter (MOLA) data on 5 arcs between March and December 1999. Inter-arc and intra-arc crossovers at 21343 points were included in the orbit solutions. The gravity model was derived using a Kaula type constraint: sqrt(2)*13*10**(-5)/L**2 (Kaula, W.M., Theory of Satellite Geodesy, Blaisdell, Waltham, MA, 1966). The analysis and results were described by F.G. Lemoine, D.D. Rowlands, D.E. Smith, D.S. Chinn, G.A. Neumann, and M.T. Zuber at the Spring Meeting of the American Geophysical Union, May 30 - June 3, 2000, Washington. DC. Further improvements to the model are expected as additional MGS data are incorporated. This product is a set of two ASCII tables: a header table and a coefficients table. Definitions of the tables follow. This Mars gravity model was produced by F.G. Lemoine under the direction of D.E. Smith of the MGS Radio Science Team. A reference for this gravity model is as follows: An improved solution of the gravity field of Mars (GMM-2B) from Mars Global Surveyor, F.G. Lemoine, D.E. Smith, D.D. Rowlands, M.T. Zuber, G.A. Neumann, D.S. Chinn, and D.E. Pavlis, J. Geophys. Res., 106(E10), pp. 23359-23376. October 25, 2001." START_TIME = 1997-10-13T00:00:00 STOP_TIME = 2000-02-29T12:05:00 START_ORBIT_NUMBER = 19 STOP_ORBIT_NUMBER = 4375 PRODUCT_CREATION_TIME = 2000-09-18T00:00:00.000 PRODUCER_FULL_NAME = "FRANK G. LEMOINE" PRODUCER_INSTITUTION_NAME = "GODDARD SPACE FLIGHT CENTER" PRODUCT_VERSION_TYPE = "FINAL" PRODUCER_ID = "MRO GST" SOFTWARE_NAME = "SOLVE.F90INLINE3;2000.01" OBJECT = SHBDR_HEADER_TABLE ROWS = 1 COLUMNS = 9 ROW_BYTES = 56 INTERCHANGE_FORMAT = BINARY DESCRIPTION = "The SHBDR Header includes descriptive information about the spherical harmonic coefficients that follow in SHBDR_COEFFICIENTS_TABLE. The header consists of a single record of nine data columns requiring 56 bytes. The Header is followed by a pad of binary integer zeroes to ensure alignment with RECORD_BYTES." OBJECT = COLUMN NAME = "REFERENCE RADIUS" DATA_TYPE = IEEE_REAL START_BYTE = 1 BYTES = 8 UNIT = "KILOMETER" DESCRIPTION = "The assumed reference radius of the spherical planet." END_OBJECT = COLUMN OBJECT = COLUMN NAME = "CONSTANT" DATA_TYPE = IEEE_REAL START_BYTE = 9 BYTES = 8 UNIT = "N/A" DESCRIPTION = "For a gravity field model the gravitational constant GM in km cubed per seconds squared for the planet. For a topography model, set to 1" END_OBJECT = COLUMN OBJECT = COLUMN NAME = "UNCERTAINTY IN CONSTANT" DATA_TYPE = IEEE_REAL START_BYTE = 17 BYTES = 8 UNIT = "N/A" DESCRIPTION = "For a gravity field model the uncertainty in the gravitational constant GM in km cubed per seconds squared for the planet. For a topography model, set to 0." END_OBJECT = COLUMN OBJECT = COLUMN NAME = "DEGREE OF FIELD" DATA_TYPE = MSB_INTEGER START_BYTE = 25 BYTES = 4 UNIT = "N/A" DESCRIPTION = "Degree of the model field." END_OBJECT = COLUMN OBJECT = COLUMN NAME = "ORDER OF FIELD" DATA_TYPE = MSB_INTEGER START_BYTE = 29 BYTES = 4 UNIT = "N/A" DESCRIPTION = "Order of the model field." END_OBJECT = COLUMN OBJECT = COLUMN NAME = "NORMALIZATION STATE" DATA_TYPE = MSB_INTEGER START_BYTE = 33 BYTES = 4 UNIT = "N/A" DESCRIPTION = "The normalization indicator. For gravity field: 0 coefficients are unnormalized 1 coefficients are normalized 2 other." END_OBJECT = COLUMN OBJECT = COLUMN NAME = "NUMBER OF NAMES" DATA_TYPE = MSB_INTEGER START_BYTE = 37 BYTES = 4 UNIT = "N/A" DESCRIPTION = "Number of valid names in the SHBDR Names Table. Also, the number of valid coefficients in the SHBDR Coefficients Table." END_OBJECT = COLUMN OBJECT = COLUMN NAME = "REFERENCE LONGITUDE" POSITIVE_LONGITUDE_DIRECTION = "EAST" DATA_TYPE = IEEE_REAL START_BYTE = 41 BYTES = 8 UNIT = "DEGREE" DESCRIPTION = "The reference longitude for the spherical harmonic expansion; normally 0." END_OBJECT = COLUMN OBJECT = COLUMN NAME = "REFERENCE LATITUDE" DATA_TYPE = IEEE_REAL START_BYTE = 49 BYTES = 8 UNIT = "DEGREE" DESCRIPTION = "The reference latitude for the spherical harmonic expansion; normally 0." END_OBJECT = COLUMN END_OBJECT = SHBDR_HEADER_TABLE OBJECT = SHBDR_NAMES_TABLE ROWS = 6558 COLUMNS = 1 ROW_BYTES = 8 INTERCHANGE_FORMAT = BINARY DESCRIPTION = "The SHBDR Names Table contains names for the solution parameters (including gravity field coefficients) which will follow in SHBDR_COEFFICIENTS_TABLE. The order of the names in SHBDR_NAMES_TABLE corresponds identically to the order of the parameters in SHBDR_COEFFICIENTS_TABLE. Each coefficient name is of the form Cij or Sij where i is the degree of the coefficient and j is the order of the coefficient. Both indices are three- digit zero-filled right-justified ASCII character strings (for example, C010005 for the 10th degree 5th order C coefficient, or S002001 for the 2nd degree 1st order S coefficient). The eighth byte in the table is an ASCII blank used to ensure that the row length is equal to RECORD_BYTES. Names of other solution parameters are limited to 8 ASCII characters; if less than 8, they will be left-justified and padded with ASCII blanks. The Names Table itself will be padded with ASCII blanks, if necessary, so that its length is an integral multiple of RECORD_BYTES." OBJECT = COLUMN NAME = "PARAMETER NAME" DATA_TYPE = CHARACTER START_BYTE = 1 BYTES = 8 UNIT = "N/A" DESCRIPTION = "The name of the coefficient or other solution parameter, left- justified and padded with ASCII blanks (if needed) to 8 characters." END_OBJECT = COLUMN END_OBJECT = SHBDR_NAMES_TABLE OBJECT = SHBDR_COEFFICIENTS_TABLE ROWS = 6558 COLUMNS = 1 ROW_BYTES = 8 INTERCHANGE_FORMAT = BINARY DESCRIPTION = "The SHBDR Coefficients Table contains the coefficients and other solution parameters for the spherical harmonic model. The order of the coefficients in this table corresponds exactly to the order of the coefficient and parameter names in SHBDR_NAMES_TABLE. The SHBDR Coefficients Table will be padded with double precision DATA_TYPE zeroes so that its total length is an integral multiple of RECORD_BYTES." OBJECT = COLUMN NAME = "COEFFICIENT VALUE" DATA_TYPE = IEEE_REAL START_BYTE = 1 BYTES = 8 UNIT = "N/A" DESCRIPTION = "A coefficient Cij or Sij or other solution parameter as specified in the SHBDR Names Table." END_OBJECT = COLUMN END_OBJECT = SHBDR_COEFFICIENTS_TABLE OBJECT = SHBDR_COVARIANCE_TABLE ROWS = 21506961 COLUMNS = 1 ROW_BYTES = 8 INTERCHANGE_FORMAT = BINARY DESCRIPTION = "The SHBDR Covariance Table contains the covariances for the spherical harmonic model coefficients and other solution parameters. The order of the covariances in this table is defined by the product of the SHBDR Names Table with its transpose, except that redundant terms are omitted on their second occurrence. The SHBDR Covariance Table will be padded with double precision DATA_TYPE zeroes so that its total length is an integral multiple of RECORD_BYTES." OBJECT = COLUMN NAME = "COVARIANCE VALUE" DATA_TYPE = IEEE_REAL START_BYTE = 1 BYTES = 8 UNIT = "N/A" DESCRIPTION = "The covariance value for the coefficients and other solution parameters specified by the product of SHBDR_NAMES_TABLE with its transpose, after omitting redundant terms." END_OBJECT = COLUMN END_OBJECT = SHBDR_COVARIANCE_TABLE END APPENDIX C.2 EXAMPLE SHBDR DATA OBJECT OUTPUT The following lists the first few lines from an example SHBDR file, the GGM2BC80.SHB Gravity field solution covariance. We describe below the extracts from a FORTRAN program to read the above GGM2BC280.SHB covariance file, the error covariance of the gravity solution GMM2B. The SHB file is opened with the following FORTRAN open statement. The key is that the SHB file is a direct access binary file with a record length (in this example) of 512 bytes. i.e. open (10, file='ggm2bc80.shb', status ='old', access='DIRECT', RECL=512) The first record reads the general solution information, where the variables have been carefully predefined at the top of the program. ................................... real*8 ae, gm, gmsig, reflon, reflat integer*4 lmax,mmax,inorm, nvar read(10,rec=1)ae, gm, gmsig, lmax, mmax, inorm, nvar, reflon, reflat ................................... On output these records are: ae = 3397.0 gm = 42828.371901 | GM in km**3/sec**2 gmsig = 7.40E-05 | GM sigma in km**3/sec**2 lmax = 80 mmax = 80 inorm = 1 nvar = 6558 | total number of parameters in the solution. reflon = 0.0E+0 reflat = 0.0E+0 The next step is to read the coefficient name table and compute the number of lines in the coefficient name table. In this example file there are 64 8 byte characters per record of 512 bytes. ..................... nline = (nvar/64) + 1 ..................... c integer multiplication on the following line is intentional c we need to know number of variables on the last line .......................... jend = nvar - (nvar/64)*64 .......................... Record 2, or the first record of the names table contains the following: C002000 C002001 C002002 C003000 C003001 C003002 C003003 C004000 C004001 C004002 C004003 C004004 C005000 C005001 C005002 C005003 C005004 C005005 C006000 C006001 C006002 C006003 C006004 C006005 C006006 C007000 C007001 C007002 C007003 C007004 C007005 C007006 C007007 C008000 C008001 C008002 C008003 C008004 C008005 C008006 C008007 C008008 C009000 C009001 C009002 C009003 C009004 C009005 C009006 C009007 C009008 C009009 C010000 C010001 C010002 C010003 C010004 C010005 C010006 C010007 C010008 C010009 C010010 C011000 Record 104 contains the last few coefficient names of the solution+GM: S080052 S080053 S080054 S080055 S080056 S080057 S080058 S080059 S080060 S080061 S080062 S080063 S080064 S080065 S080066 S080067 S080068 S080069 S080070 S080071 S080072 S080073 S080074 S080075 S080076 S080077 S080078 S080079 S080080 GM The Coefficients table begins at Record 105: The first eight variables of that record are: -0.87451D-03 0.13938D-09 -0.84178D-04 -0.11887D-04 0.39053D-05 -0.15863D-04 0.35339D-04 0.51258D-05 The first coefficient value is for C20. The Coefficients table ends at Record 207 with 30 valid records and the remainder zero filled: -0.39660D-07 0.25145D-08 0.27213D-07 0.60636D-07 0.25307D-07 0.40813D-08 0.16849D-07 0.16050D-07 -0.30849D-07 -0.26461D-07 -0.79262D-08 0.35247D-07 0.53467D-08 0.33029D-07 0.35339D-07 0.28539D-07 -0.30311D-10 0.38384D-07 -0.19836D-07 0.75625D-07 -0.19420D-07 0.34309D-09 -0.17577D-07 0.36022D-07 0.42967D-07 0.42482D-07 -0.40326D-07 -0.19721D-07 -0.53860D-07 0.42828D+14 .......... The last valid record is the value of GM for this solution, as per the order specified in the names record.