AAS Paper 99-328 Presented at the AAS/AIAA Astrodynamics Specialist conference Girdwood, Alaska, August 16-19, 1999 Orbit Determination for Mars Global Surveyor During Mapping F. G. Lemoine, D.D. Rowlands and D. E. Smith Laboratory for Terrestrial Physics NASA Goddard Space Flight Center D. S. Chinn, D. E. Pavlis and S. B. Luthcke Raytheon ITSS Greenbelt, Maryland G. A. Neumann and M. T. Zuber, Department of Earth, Atmospheric, and Planetary Sciences Massachussetts Institute of Technology Cambridge, Massachusetts

Other links. Mars Global Surveyor. MGS Radio Science Team. Mars Orbiter Laser Altimeter (MOLA). Goddard Mars Model-2B (GMM-2B) (spherical harmonic model of the Mars gravity field to 80x80).

Abstract:

The Mars Global Surveyor (MGS) spacecraft reached its designated low-altitude, and near-circular orbit about Mars after termination of aerobraking on February 4, 1999. The Mars Orbiter Laser Altimeter (MOLA) returned its first data from this low-altitude orbit on March 1, 1999. The Doppler data acquired from the Deep Space Network were used to determine the orbit of the MGS spacecraft, so that the altimeter data could be used to map the topography of Mars. A detailed nonconservative force model was implemented for MGS that included articulation of the solar arrays. The tracking data in February and March 1999 were used to improve the knowledge of the Mars geopotential by developing MGM0964C20, a solution to 70x70 in spherical harmonics. When the improved nonconservative force model and the improved Mars gravity model, MGM0964C20, are applied in the MGS orbit determination during the mapping orbit, the overlaps of adjacent arcs in March 1999 show a consistency of 0.6 m in the radial direction, and 2 meters in total position. We demonstrate that altimeter crossovers from MOLA can be used to further improve the orbit determination for these arcs resulting in an orbit overlap consistency of 0.3 meters in the radial direction and 1.7 meters in total position.