PDS_VERSION_ID = "PDS3" FILE_NAME = "JGM75B01.SHB" RECORD_TYPE = FIXED_LENGTH RECORD_BYTES = 512 FILE_RECORDS = 260600 ^SHBDR_HEADER_TABLE = ("JGM75B01.SHB",1) ^SHBDR_NAMES_TABLE = ("JGM75B01.SHB",2) ^SHBDR_COEFFICIENTS_TABLE = ("JGM75B01.SHB",93) ^SHBDR_COVARIANCE_TABLE = ("JGM75B01.SHB",184) INSTRUMENT_HOST_NAME = "MARS GLOBAL SURVEYOR" TARGET_NAME = "MARS" INSTRUMENT_NAME = "RADIO SCIENCE SUBSYSTEM" DATA_SET_ID = "MGS-M-RSS-5-SDP-V1.0" OBSERVATION_TYPE = "GRAVITY FIELD" PRODUCT_ID = "JGM75B01.SHB" PRODUCT_RELEASE_DATE = 1999-09-28 DESCRIPTION = " This file contains coefficients, formal error covariance, and related data for the MGS75B Spherical Harmonic Model of the Mars gravity field. MGS75B is a 75x75 spherical harmonics model with power rule constraints applied to harmonics above degree 45. It was derived from radio tracking of the Viking Orbiter 1, Viking Orbiter 2, and Mars Global Surveyor spacecraft during the times listed below: Viking Orbiter 1 1977-03-11 to 1978-12-22 Viking Orbiter 2 1976-08-07 to 1977-10-23 1977-10-23 to 1978-07-23 Mars Global Surveyor 1998-03-28 to 1998-04-24 (SPO-1) 1998-06-04 to 1998-09-23 (SPO-2) 1999-02-02 to 1999-03-29 (GCO) Specific details for this model are: The spherical harmonic coefficients are fully normalized. The associated GM = 42828.385943 km**3/sec**2 The reference radius = 3394.20 km The Mars-fixed reference frame is given by the IAU 1991 constants The radio tracking data blocks consist of: Viking 1 at 310 km periapsis with 60622 observations; Viking 2 at 775 km periapsis with 42451 observations; Viking 2 at 300 km periapsis with 36531 observations; MGS SPO-1 and SPO-2 at 177 km periapsis with 133,725 observations; MGS GCO at 370 km periapsis with 125,889 observations. The apriori and data weights for each block have accounted for the S-band Doppler on Viking being corrupted by space plasma and the SPO-1 and SPO-2 Doppler being corrupted by solar plasma while at small sun-earth-probe angles. The GCO data are the highest quality data having a Doppler data weight of 0.1 mm/sec for a 10 second sample. The main contribution of the MGS GCO data is its global data coverage with a mean altitude about 400 km. Correlation of gravity anomaly with surface images from the MOLA topography is generally strong for large/medium scale features. For additional details see Smith et al., 'The Gravity Field of Mars: Results from Mars Global Surveyor', SCIENCE, 286, 94-97, 1999. This product is a set of four binary tables: a header table, a names table, a coefficients table, and a covariance table. Definitions of the tables follow. The coefficients and formal error covariance of MGS75B is delivered in the Spherical Harmonics Gravity binary Data Record (SHGBDR) and is produced by the Mars Global Surveyor Gravity Science Team at JPL under the direction of William L. Sjogren. NB: Orbit numbers in keywords below are counted from Mars Orbit Insertion in September 1997. The MGS Project reset its orbit count at the beginning of Mapping in early March 1999; the reset is not included in either START_ORBIT_NUMBER or STOP_ORBIT_NUMBER." START_ORBIT_NUMBER = 202 STOP_ORBIT_NUMBER = 1930 START_TIME = 1998-03-28T00:00:00 STOP_TIME = 1999-03-29T05:30:00 PRODUCT_CREATION_TIME = 1999-09-28T00:00:00.000 PRODUCER_FULL_NAME = "WILLIAM L. SJOGREN" PRODUCER_INSTITUTION_NAME = "JET PROPULSION LABORATORY" PRODUCT_VERSION_TYPE = "PRELIMINARY" PRODUCER_ID = "MGS GRAVSCI TEAM" SOFTWARE_NAME = "SHBGRV;V1.0" 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 which 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 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 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 = 5773 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 = 5773 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 = 16666651 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 as the (top to bottom) elements of successive column vectors (left to right) in the upper triangular matrix formed by the product of the SHBDR Names Table with its transpose. For example, if the names table has four entries A, B, C, D, then the covariances are given by the column vectors in the upper triangular matrix of | A | [ A B C D ] = | AA AB AC AD | | B | | BA BB BC BD | | C | | CA CB CC CD | | D | | DA DB DC DD | That is, the covariance table will list (in this order) AA, AB, BB, AC, BC, CC, AD, BD, CD, and DD. 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