PDS_VERSION_ID = PDS3 RECORD_TYPE = FIXED_LENGTH RECORD_BYTES = 122 FILE_RECORDS = 4185 ^SHADR_HEADER_TABLE = ("GGM1041C.SHA",1) ^SHADR_COEFFICIENTS_TABLE = ("GGM1041C.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 = "MGM1041C" PRODUCT_ID = "GGM1041C.SHA" PRODUCT_RELEASE_DATE = 2003-03-28 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. Coordinate system is IAU 2000 (Seidelmann et al., Celestial Mechanics and Dynamical Astronomy, 82(1), 83-110, January 2002). Constants relevant for Mars in IAU 2000 are: alpha (right ascension) = 317.68143 deg - 0.1061 deg/century delta (declination) = 52.88650 deg - 0.0609 deg/century Wo (prime meridian) = 176.630 deg Wdot = 350.89198226 deg/day Gravitational constants obtained from the solution are: GM (Mars) = 4.282837024529127 E+13 m**3/s**2 sigma = 0.617 E+05 m**3/s**2 GM (Phobos) = 0.68012569 E+06 m**3/s**2 sigma = 0.842 E+04 m**3/s**2 The model was constructed from 2,568,683 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 May 2002 after the orbit was circularized. Time Periods Total Arcs Observations ------------------------ ---- ------------ Hiatus 2 24119 SPO-1 8 31014 SPO-2 17 144253 Feb-Mar 1999 10 86069 2 Apr 1999 - 22 May 2002 167 2186533 Doppler + Crossovers 5 96875 ------------------------ ---- ------------ Total 2568863 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 21679 points were included in the orbit solutions. Crossovers poleward of 60 degrees north and south were excluded to avoid possible contamination by any time-varying signature in the polar caps. The altimeter data were edited for large off-nadir angles as well as for the roughness and slope of the terrain. The crossovers supplemented the normal radiometric tracking for these arcs, which included 75196 Doppler and range observations. One-way Doppler data were included once these data started to become available in March 2000 (just after the start of the first Beta Supplement operations). Range biases were adjusted on a pass by pass basis, and frequency biases were adjusted for the one-way data. The Gravity Calibration Orbit (GCO, February 1999) data were weighted at 0.0044 Hz (0.16 mm/s). Data for 2000 and for 2001 through the start of Relay 16 operations were weighted at 0.18 mm/s. Data after the start of Relay 16 operations in 2001 were weighted at 0.357 mm/s in light of the higher RMS fit for these data. The one-way data were downweighted with respect to the two-way data by a factor of 2, and are thus weighted at 0.36 mm/s for the 2000-2001 data and at 0.71 mm/s for Relay 16. Compared to the GMM2B model, this model contains about 2.5 times as much data. The data were also rigorously re-edited to remove spurious signatures which were particularly apparent in some of the arcs with one-way Doppler data. Finally, the non-conservative force model was refined to include the high gain antenna. This improvement reduced the average solar radiation reflectivity (Cr) from 1.15 to 1.05. 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). 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." START_TIME = 1997-10-13T00:00:00 STOP_TIME = 2002-05-27T23:59:59 PRODUCT_CREATION_TIME = 2003-02-05T20:34:50 PRODUCER_FULL_NAME = "FRANK G. LEMOINE" PRODUCER_INSTITUTION_NAME = "GODDARD SPACE FLIGHT CENTER" PRODUCT_VERSION_TYPE = "FINAL" PRODUCER_ID = "MGS RST" SOFTWARE_NAME = "SOLVE;200201.02" 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 = 4183 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