PDS_VERSION_ID = PDS3 RECORD_TYPE = FIXED_LENGTH RECORD_BYTES = 122 FILE_RECORDS = 3320 ^SHADR_HEADER_TABLE = ("GGM1025A.SHA",1) ^SHADR_COEFFICIENTS_TABLE = ("GGM1025A.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 = "MGM1025" PRODUCT_ID = "GGM1025A.SHA" PRODUCT_RELEASE_DATE = 2002-01-01 DESCRIPTION = " 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. The MGM1025 gravity model is an update to the GMM-2B gravity model. It was determined from 155 arcs of MGS tracking data in Hiatus, SPO, GCO and Mapping. MGM1025 includes the same Mapping and GCO data as were in GMM2B; in addition, it includes data from the first half of 2001 (through July 21, 2001) when the MGS orbit orientation angle with respect to the line-of-sight (LOS) was optimum for gravity measurements. It excludes data in the vicinity of solar conjunction from May 08 to July 30 in 2000. Comparison of GMM2B and MGM1025 -------------------------------- GMM2B MGM1025 -------- -------- Model Size 80x80 80x80 Coordinate System IAU 1991 IAU 2000 Observations ------------ Hiatus 24,119 24,119 SPO-1 31,001 31,014 SPO-2 157,972 136,667 GCO 76,813 80,795 Mapping 665,210 1,352,661 TOTAL 955,155 1,625,276 Number of Arcs -------------- Hiatus 2 2 SPO-1 8 8 SPO-2 16 14 GCO 9 9 Mapping 47 122 MGM1025 has improved correlation with topogaphy compared with GMM-2B. The average correlation with MOLA derived topography (through degree 70) is 0.722 for GMM-2B and 0.756 for MGM1025. The new model has slightly greater power in the band from l=60 to 70. The average RMS of fit to the F2 (two-way) tracking data is 0.13 to 0.20 mm/s with this model, excluding arcs in the vicinity of solar conjunction. The average RMS of fit for the one-way (F1) Doppler tracking with this model is 0.10 to 0.15 mm/s. The one-way data contribute to solutions starting sporadically in February 2000 and more consistently in arcs starting in March of 2000. They are used solely to fill in what would otherwise be gaps in the two-way tracking. Frequency biases are estimated for each pass of one-way data. The coordinate system for the new model is IAU 2000 (Seidelman et al., Cel. Mech. Dyn. Astron, 82, 83-110, 2002), defined by the Mars Cartography Working Group. It includes updates to the orientation of the Mars Pole and rotation rate from a joint Pathfinder/Viking solution, and a re-determination of the location of the prime meridian (with respect to the crater Airy-0) from Mars Global Surveyor MOC and MOLA data. Pole right ascension (alpha) and declination (delta), prime meridian (Wo), and rotation rate (Wodot) in IAU 2000 are: alpha = 317.68143 deg -0.1061 deg/century delta = 52.88650 deg -0.0609 deg/century Wo = 176.630 deg Wdot = 350.89198266 deg/day The analysis and results for MGM1025 were described by F.G. Lemoine, G.A. Neumann, D.S. Chinn, D.E. Smith, M.T. Zuber, D.D. Rowlands, D.P. Rubincam, and D.E. Pavlis in 'Solution for Mars Geophysical Parameters from Mars Global Surveyor Tracking Data', American Geophysical Union Fall Meeting 2001 (EOS, Trans. AGU 82(47), Fall Meeting Supplement, Abstract P42A-0545, F721, 2001). The GMM2B model was described by Lemoine et al., 'An Improved Solution of the Gravity Field of Mars (GMM-2B) from Mars Global Surveyor', J. Geophys Res., 106(E10), 23359-23376, Oct 25, 2001. 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." START_TIME = 1997-10-13T00:00:00 STOP_TIME = 2001-07-21T23:59:39 START_ORBIT_NUMBER = 19 STOP_ORBIT_NUMBER = 10596 PRODUCT_CREATION_TIME = 2001-11-01T22:50:36 PRODUCER_FULL_NAME = "FRANK G. LEMOINE" PRODUCER_INSTITUTION_NAME = "GODDARD SPACE FLIGHT CENTER" PRODUCT_VERSION_TYPE = "FINAL" PRODUCER_ID = "MGS RST" SOFTWARE_NAME = "SOLVE;9603.02" 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 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 = 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 km cubed per seconds squared for the planet (or, set to 0 if not known). 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 = "Degree of the 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 = "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 = 3318 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