urn:nasa:pds:mgs-rss:data-sha:jgm75a01 1.0 1.22.0.0 Product_Observational 2025 MGS RSS This file contains coefficients and related data for the spherical harmonic model MGS75A of the Mars gravity field. MGS75A was derived from radio tracking of the Mariner 9, Viking 1 Orbiter, Viking 2 Orbiter, and Mars Global Surveyor spacecraft. The Mars-fixed reference frame is given by the IAU 1991 constants. The data cover 1997-09-12T00:00:00.000Z to 1998-09-23T23:59:59.999Z. William Sjogren 1 Jet Propulsion Laboratory https://ror.org/027k65916 2025-02-25 1.0 This product, JGM75A01.SHA, was originally released as part of the PDS3 MGS-M-RSS-5-SDP-V1.0 data set. The metadata have been migrated to PDS4. The data themselves are unchanged. 1997-09-12T00:00:00.000Z 1998-09-23T23:59:59.999Z Science Derived Mars Global Surveyor Spherical Harmonic Model ASCII Data Mars Global Surveyor Mission urn:nasa:pds:context:investigation:mission.mars_global_surveyor data_to_investigation Mars Global Surveyor Host urn:nasa:pds:context:instrument_host:spacecraft.mgs is_instrument_host Mariner 9 Host urn:nasa:pds:context:instrument_host:spacecraft.mr9 is_instrument_host Viking Orbiter 1 Host urn:nasa:pds:context:instrument_host:spacecraft.vo1 is_instrument_host Viking Orbiter 2 Host urn:nasa:pds:context:instrument_host:spacecraft.vo2 is_instrument_host Radio Science Subsystem (RSS) Instrument urn:nasa:pds:context:instrument:mgs.rss is_instrument Radio Science Subsystem (RSS) Instrument urn:nasa:pds:context:instrument:rss.mr9 is_instrument Radio Science Subsystem (RSS) Instrument urn:nasa:pds:context:instrument:rss.vo1 is_instrument Radio Science Subsystem (RSS) Instrument urn:nasa:pds:context:instrument:rss.vo2 is_instrument Mars Planet urn:nasa:pds:context:target:planet.mars data_to_target 1 572 MGS-M-RSS-5-SDP-V1.0:JGM75A01.SHA:JGM75A01.SHA data_to_derived_source_product 10.17189/1519757 PDS Planetary Plasma Interactions Node This is the first version converted to PDS4. The DOI references the source PDS3 data set. JGM75A01.SHA 1999-09-09T14:39:47 357094 c3b2ff34428273eb90f4282b28ba634a MGS Spherical Harmonic ASCII MGS75A Model Header 1997-09-12 - 1998-09-23 0 1 Carriage-Return Line-Feed 8 0 244 Reference Radius 1 1 ASCII_Real 23 The assumed reference radius of the spherical planet. Constant 2 25 ASCII_Real 23 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. Uncertainty in Constant 3 49 ASCII_Real 23 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. Degree of Field 4 73 ASCII_Integer 5 deg of the model field. Order of Field 5 79 ASCII_Integer 5 Order of the model field. Normalization State 6 85 ASCII_Integer 5 The normalization indicator. For gravity field: 0 coefficients are unnormalized 1 coefficients are normalized 2 other. Reference Longitude 7 91 ASCII_Real 23 deg The reference longitude for the spherical harmonic expansion; normally 0. Reference Latitude 8 115 ASCII_Real 23 deg The reference latitude for the spherical harmonic expansion; normally 0. MGS Spherical Harmonic ASCII MGS75A Model Coefficients Table 1997-09-12 - 1998-09-23 244 356850 PDS DSV 1 Although there are approximately 4000 Mariner 9, 14000 Viking, and 134000 MGS observations incorporated in the solution, the observations do not provide uniform coverage. The Mariner 9 data are from a very eccentric orbit with periapsis altitudes of 1400 km and periapsis latitudes near equatorial (very high altitudes over the poles). The Viking data are much better with periapsis altitudes of 300 km; but the latitudes of periapsis were almost all in the northern hemisphere (only a few at 40 degrees south with an orbit inclination of 40 degrees. The MGS data provide excellent new coverage over the north polar region with periapsis latitudes ranging from 65-85 degrees north and altitudes of 180 km. But the southern hemisphere gravity remains very poorly defined and at about the same state of knowledge as before MGS. 2925 Carriage-Return Line-Feed Comma 6 0 Coefficient Degree 1 ASCII_Integer 5 %5d The degree index m of the C and S coefficients in this record. Coefficient Order 2 ASCII_Integer 5 %5d The order index n of the C and S coefficients in this record. C 3 ASCII_Real 23 %23.16e The coefficient Cmn for this spherical harmonic model. S 4 ASCII_Real 23 %23.16e The coefficient Smn for this spherical harmonic model. C Uncertainty 5 ASCII_Real 23 %23.16e The uncertainty in the coefficient Cmn for this spherical harmonic model. S Uncertainty 6 ASCII_Real 23 %23.16e The uncertainty in the coefficient Smn for this spherical harmonic model.