PDS_VERSION_ID = "PDS3" RECORD_TYPE = FIXED_LENGTH RECORD_BYTES = 122 FILE_RECORDS = 2927 ^SHADR_HEADER_TABLE = ("JGM75B01.SHA",1) ^SHADR_COEFFICIENTS_TABLE = ("JGM75B01.SHA",3) 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" ORIGINAL_PRODUCT_ID = "MGS75B" PRODUCT_ID = "JGM75B01.SHA" PRODUCT_RELEASE_DATE = 1999-09-28 DESCRIPTION = " This file contains coefficients 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 file is a pair of ASCII tables: a header table and a table of 5772 coefficients (plus a value for GM). Definitions of the tables follow. The MGS75B gravity model is delivered in the Spherical Harmonics Gravity ASCII Data Record (SHGADR) 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 = "SHAGRV.V1.0" OBJECT = SHADR_HEADER_TABLE ROWS = 1 COLUMNS = 8 ROW_BYTES = 137 ROW_SUFFIX_BYTES = 107 INTERCHANGE_FORMAT = ASCII DESCRIPTION = "The SHADR header includes descriptive information about the spherical harmonic coefficients which follow in SHADR_COEFFICIENTS_TABLE. The header consists of a single record of eight (delimited) data columns requiring 137 bytes, a pad of 105 unspecified ASCII characters, an ASCII carriage-return, and an ASCII line-feed." OBJECT = COLUMN NAME = "REFERENCE RADIUS" DATA_TYPE = ASCII_REAL START_BYTE = 1 BYTES = 23 FORMAT = "E23.16" UNIT = "KILOMETER" DESCRIPTION = "The assumed reference radius of the spherical planet." END_OBJECT = COLUMN OBJECT = COLUMN NAME = "CONSTANT" DATA_TYPE = ASCII_REAL START_BYTE = 25 BYTES = 23 FORMAT = "E23.16" 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 = ASCII_REAL START_BYTE = 49 BYTES = 23 FORMAT = "E23.16" 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 = ASCII_INTEGER START_BYTE = 73 BYTES = 5 FORMAT = "I5" UNIT = "N/A" DESCRIPTION = "The degree of model field." END_OBJECT = COLUMN OBJECT = COLUMN NAME = "ORDER OF FIELD" DATA_TYPE = ASCII_INTEGER START_BYTE = 79 BYTES = 5 FORMAT = "I5" UNIT = "N/A" DESCRIPTION = "The order of the model field." END_OBJECT = COLUMN OBJECT = COLUMN NAME = "NORMALIZATION STATE" DATA_TYPE = ASCII_INTEGER START_BYTE = 85 BYTES = 5 FORMAT = "I5" 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 = "REFERENCE LONGITUDE" POSITIVE_LONGITUDE_DIRECTION = "EAST" DATA_TYPE = ASCII_REAL START_BYTE = 91 BYTES = 23 FORMAT = "E23.16" UNIT = "DEGREE" DESCRIPTION = "The reference longitude for the spherical harmonic expansion; normally 0." END_OBJECT = COLUMN OBJECT = COLUMN NAME = "REFERENCE LATITUDE" DATA_TYPE = ASCII_REAL START_BYTE = 115 BYTES = 23 FORMAT = "E23.16" UNIT = "DEGREE" DESCRIPTION = "The reference latitude for the spherical harmonic expansion; normally 0." END_OBJECT = COLUMN END_OBJECT = SHADR_HEADER_TABLE OBJECT = SHADR_COEFFICIENTS_TABLE ROWS = 2925 COLUMNS = 6 ROW_BYTES = 107 ROW_SUFFIX_BYTES = 15 INTERCHANGE_FORMAT = ASCII DESCRIPTION = "The SHADR coefficients table contains the coefficients for the spherical harmonic model. Each row in the table contains the degree index m, the order index n, the coefficients Cmn and Smn, and the uncertainties in Cmn and Smn. The (delimited) data require 107 ASCII characters; these are followed by a pad of 13 unspecified ASCII characters, an ASCII carriage- return, and an ASCII line-feed." OBJECT = COLUMN NAME = "COEFFICIENT DEGREE" DATA_TYPE = ASCII_INTEGER START_BYTE = 1 BYTES = 5 FORMAT = "I5" UNIT = "N/A" DESCRIPTION = "The degree index m of the C and S coefficients in this record." END_OBJECT = COLUMN OBJECT = COLUMN NAME = "COEFFICIENT ORDER" DATA_TYPE = ASCII_INTEGER START_BYTE = 7 BYTES = 5 FORMAT = "I5" UNIT = "N/A" DESCRIPTION = "The order index n of the C and S coefficients in this record." END_OBJECT = COLUMN OBJECT = COLUMN NAME = "C" DATA_TYPE = ASCII_REAL START_BYTE = 13 BYTES = 23 FORMAT = "E23.16" UNIT = "N/A" DESCRIPTION = "The coefficient Cmn for this spherical harmonic model." END_OBJECT = COLUMN OBJECT = COLUMN NAME = "S" DATA_TYPE = ASCII_REAL START_BYTE = 37 BYTES = 23 FORMAT = "E23.16" UNIT = "N/A" DESCRIPTION = "The coefficient Smn for this spherical harmonic model." END_OBJECT = COLUMN OBJECT = COLUMN NAME = "C UNCERTAINTY" DATA_TYPE = ASCII_REAL START_BYTE = 61 BYTES = 23 FORMAT = "E23.16" UNIT = "N/A" DESCRIPTION = "The uncertainty in the coefficient Cmn for this spherical harmonic model." END_OBJECT = COLUMN OBJECT = COLUMN NAME = "S UNCERTAINTY" DATA_TYPE = ASCII_REAL START_BYTE = 85 BYTES = 23 FORMAT = "E23.16" UNIT = "N/A" DESCRIPTION = "The uncertainty in the coefficient Smn for this spherical harmonic model." END_OBJECT = COLUMN END_OBJECT = SHADR_COEFFICIENTS_TABLE END