urn:nasa:pds:mgs-rss:data-sha:ggm1025a 1.0 1.22.0.0 Product_Observational 2025 MGS RSS This file contains coefficients and related data for the spherical harmonic model MGM1025 of the Mars gravity field. Input data are from radio tracking of the Mars Global Surveyor spacecraft. The MGM1025 gravity model is an update to the GMM-2B gravity model. The data cover 1997-10-13T00:00:00Z to 2001-07-21T23:59:39Z. Frank Lemoine 1 Goddard Space Flight Center https://ror.org/0171mag52 David Smith 2 Goddard Space Flight Center https://ror.org/0171mag52 2025-02-11 1.0 This product, GGM1025A.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. 1997-10-13T00:00:00Z 2001-07-21T23:59:39Z 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 Radio Science Subsystem (RSS) Instrument urn:nasa:pds:context:instrument:mgs.rss is_instrument Mars Planet urn:nasa:pds:context:target:planet.mars data_to_target 19 10596 urn:nasa:pds:mgs-rss:browse:ggm1025a::1.0 data_to_browse urn:nasa:pds:mgs-rss:data-maps:ggm1025a::1.0 data_to_derived_product urn:nasa:pds:mgs-rss:data-maps:ggm1025b::1.0 data_to_derived_product 10.1023/A:1013939327465 P.K.S., Abalakin, V.K., Bursa, M. et al. Report of the IAU/IAG Working Group on Cartographic Coordinates and Rotational Elements of the Planets and Satellites: 2000. Celestial Mechanics and Dynamical Astronomy 82, 83-111 (2002). The coordinate system for the new model is IAU 2000 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 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 10.1029/2000JE001426 Lemoine, F. G., D. E. Smith, D. D. Rowlands, M. T. Zuber, G. A. Neumann, D. S. Chinn, and D. E. Pavlis (2001), An improved solution of the gravity field of Mars (GMM-2B) from Mars Global Surveyor, J. Geophys. Res., 106(E10), 23359-23376 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. Kaula, W.M., Theory of Satellite Geodesy, Blaisdell, Waltham, MA, 1966. The gravity model was derived using a Kaula type constraint: sqrt(2)*13*10**(-5)/L**2 where L is the spherical harmonic degree. Without this constraint, the high degree terms develop excessive power. MGS-M-RSS-5-SDP-V1.0:GGM1025A.SHA:GGM1025A.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. GGM1025A.SHA 2002-03-19T10:06:04 405040 f6cae3b96551eb1a1b45aa2c03e5981a MGS Spherical Harmonic ASCII MGM1025 Model Header 1997-10-13 - 2001-07-21 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 MGM1025 Model Coefficients Table 1997-10-13 - 2001-07-21 244 404796 PDS DSV 1 3318 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.