PDS_VERSION_ID = "PDS3" RECORD_TYPE = FIXED_LENGTH RECORD_BYTES = 122 FILE_RECORDS = 3742 ^SHADR_HEADER_TABLE = ("JGM85H02.SHA",1) ^SHADR_COEFFICIENTS_TABLE = ("JGM85H02.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 = "MGS85H2" PRODUCT_ID = "JGM85H02.SHA" PRODUCT_RELEASE_DATE = 2002-11-06 DESCRIPTION = " This file contains coefficients and related data for the MGS85H2 spherical harmonic model of the Mars gravity field. MGS85H2 is a 85x85 spherical harmonics model with power rule constraints applied to harmonics above degree 59. It was derived from radio tracking of: MGS Science Phasing Orbit 1 (SPO1) 1998-03-28 to 1998-04-28 Science Phasing Orbit 2 (SPO2) 1998-06-04 to 1998-09-23 Gravity Calibration Orbit (GCO) and Fixed High-Gain Antenna Mapping (FHGA) 1999-02-02 to 1999-03-29 Mapping (MAP) 1999-03-29 to 2002-04-14 Odyssey Transition Orbit (ODYT) 2002-01-11 to 2002-01-15 Pathfinder 1997-07-04 to 1997-10-07 Viking 1 Lander 1976-07-21 to 1982-11-13 Some details describing this model are: The spherical harmonic coefficients are fully normalized. The reference radius = 3396.0 km The prime meridian of this model matches the IAU 2000 prime meridian at the J2000 epoch to about 20cm. The Mars System GM (Mars+Phobs+Deimos) = 42828.3752203 km^3/sec^2 The GM of Mars = 42828.374440 km^3/sec^2 The GM of Phobos = 7.13x10^-4 km^3/sec^2 The GM of Deimos = 6.7x10^-5 km^3/sec^2 The Viking and Mariner 9 orbiter data are not included in this delivery unlike in the past deliveries which included this data. This data do not seem to add any more information for the gravity although there is some Phobos and Deimos GM information in the data. The values for the Phobos and Deimos GM given here do not include the Viking and Mariner 9 orbiter data. The Mars-fixed reference frame is similar to the Pathfinder Mars orientation model (Folkner et al., Science 278, 1997) but with the prime meridian being consistent with the IAU 2000 coordinate frame. The rotation from the body-fixed position rBF to the inertial postion rIN is: rIN = Rz(-N) Rx(-J) Rz(-PSI) Rx(-I) Rz(-PHI) rBF where N is the angle in the plane of the Earth-mean-equator of J2000 (EME2000) from the vernal equinox (intersection of the mean ecliptic and EME2000 planes) to the intersection of the Mars-mean-orbit of J2000 and EME2000 planes; J is the inclination of the Mars-mean-orbit plane relative to the EME2000 plane; PSI is the angle in the Mars-mean-orbit plane from the intersection of the EME2000 and Mars-mean-orbit planes to the intersection of the Mars-mean-orbit and Mars-true-equator of date planes; I is the inclination of the Mars-true-equator relative to the Mars-mean-orbit plane; PHI is the angle in the plane of the Mars-true-equator from the intersection of the Mars-mean-orbit plane and Mars-true-equator to the Mars prime meridian. PSI, I, and PHI have J2000 epoch and secular values plus corrections for nuations. PHI in addition has seasonal corrections for spin with values similar to Folkner et al., Science 278, 1997. For example, PSI = PSI(t=J2000) + (dPSI/dt)*T + dPSI(nutations) where T is time past J2000 in days. For MGS85H2, the values of the orientation angles are: N = 3.37919183 deg J = 24.67682669 deg PSI(t=J2000) = 81.9683148717 deg dPSI/dt = -0.000005781 deg/day (precession rate of Mars) I(t=J2000) = 25.1894070110 deg dI/dt = 0.000000007 deg/day PHI(t=J2000) = 133.38469 deg dPHI/dt = 350.891985267 deg/day The nutation corrections are given by Reasenberg and King, J. of Geophys. Res. 84, 1979 (see also, Folkner et al., J. of Geophys. Res. 102, 1997). Note N, J, and the nutation corrections are fixed values and PHI(t=J2000) was chosen to match the prime meridian of the IAU 2000 system. The other orientation values above were estimated when solving for the gravity field. The radio tracking data (Doppler and range) blocks consist of: MGS SPO1 and SPO2 at 177 km periapsis with 133,624 observations; MGS GCO at 370 km periapsis with 144,810 observations; MGS MAP at 370 km periapsis with 3,146,564 observations. Odyssey transistion at 200 km periapsis with 27,661 observations. Pathfinder on the Mars surface with 7,562 observations. Viking 1 Lander on the Mars surface with 15,628 observations. The data weights for each block have accounted for the SPO1 and SPO2 Doppler being corrupted by solar plasma while at small Sun-Earth-probe angles. The GCO and MAP data are the highest quality data having a 2-way Doppler data weight near 0.03 mm/sec for a 10 second sample. The Pathfinder Doppler is weighted about 0.08 mm/s and Viking Lander data is weighted near 0.4 mm/s. The k2 Love number to use with this MGS85H2 solution is 0.168. The second degree harmonic coefficients do not include the permanent tide due to the Love number. This delivery is the Mars static gravity field. However, the gravity field varies due to the mass exchange between the polar caps and the Mars atmosphere. The major component of this effect can be included in the gravity field by adding the following correction to the normalized J3 gravity coefficient: dJ3 = 2.474D-09 * sin W*(t-t0) where W is the Mars mean motion = 191.39 deg/yr and t-t0 = years past Jan 1, 1999. The Love number, seasonal gravity, and seasonal spin variation results for this gravity field are presented in Yoder et al., submitted to Science, 2002. The main contribution of the MGS GCO and MAP data is its global data coverage with a mean altitude of about 400 km. Correlation of MGS85H2 model with topography model from the MOLA is generally strong for large/medium scale features, and has been improved significantly above degree 50 compared to the MGS85F solution. This file is a pair of ASCII tables: a header table and a table of 7395 coefficients plus a value for GM. Definitions of the tables follow. The MGS85H2 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: START_ORBIT_NUMBER in keywords below is counted from Mars Orbit Insertion in September 1997. The MGS Project reset its orbit count at the beginning of Mapping in early March 1999; STOP_ORBIT_NUMBER is counted from the reset in 1999." START_ORBIT_NUMBER = 202 STOP_ORBIT_NUMBER = 13857 START_TIME = 1998-03-28T00:00:00.000 STOP_TIME = 2002-04-14T14:00:00.000 PRODUCT_CREATION_TIME = 2002-11-05T00:00:00.000 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 = 3740 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