<h2>AAS 95-314</h2><h2>Mars Gravity Field from Satellite-to-Satellite Doppler Data</h2><h4>A. Vijayaraghavan, Jet Propulsion Laboratory, Pasadena, CA</h4><h2> Abstract </h2>An accurate description of the Martian gravity field is essential to support such activities as autonomous navigation and Mars landing during future missions.  From covariance analysis for some specific cases, satellite-to-satellite (STS) Doppler data is known to be useful in accurately determining the gravitational field.  In this paper, and approximate analysis is presented to show that the knowledge of the Mars gravity field can be improved by a factor of 10 to 20 with STS Doppler data.  Both high-low and low-low satellite configurations are examined.  The analysis is in the frequency domain proceeding from two-dimensional Fourier transforms of Hill's variational equations.  The transfer functions for high-low and low-low STS data are obtained and an optimal filter is derived.  The results are applicable for the determination of short wavelength gravitational field only.<br><br>