NTRS - NASA Technical Reports Server

Back to Results
An improved gravity model for Mars: Goddard Mars Model 1Doppler tracking data of three orbiting spacecraft have been reanalyzed to develop a new gravitational field model for the planet Mars, Goddard Mars Model 1 (GMM-1). This model employs nearly all available data, consisting of approximately 1100 days of S band tracking data collected by NASA's Deep Space Network from the Mariner 9 and Viking 1 and Viking 2 spacecraft, in seven different orbits, between 1971 and 1979. GMM-1 is complete to spherical harmonic degree and order 50, which corresponds to a half-wavelength spatial resolution of 200-300 km where the data permit. GMM-1 represents satellite orbits with considerably better accuracy than previous Mars gravity models and shows greater resolution of identifiable geological structures. The notable improvement in GMM-1 over previous models is a consequence of several factors: improved computational capabilities, the use of otpimum weighting and least squares collocation solution techniques which stabilized the behavior of the solution at high degree and order, and the use of longer satellite arcs than employed in previous solutions that were made possible by improved force and measurement models. The inclusion of X band tracking data from the 379-km altitude, nnear-polar orbiting Mars Observer spacecraft should provide a significant improvement over GMM-1, particularly at high latitudes where current data poorly resolve the gravitational signature of the planet.
Document ID
Document Type
Reprint (Version printed in journal)
Smith, D. E.
(NASA Goddard Space Flight Center Greenbelt, MD, United States)
Lerch, F. J.
(NASA Goddard Space Flight Center Greenbelt, MD, United States)
Nerem, R. S.
(NASA Goddard Space Flight Center Greenbelt, MD, United States)
Zuber, M. T.
(NASA Goddard Space Flight Center Greenbelt, MD, United States)
Patel, G. B.
(Hughes STX Corporation Lanham, MD, United States)
Fricke, S. K.
(RMS Technologies, Inc. Landover, MD, United States)
Lemoine, F. G.
(Univ. of Colorado, Boulder, CO United States)
Date Acquired
August 16, 2013
Publication Date
November 25, 1993
Publication Information
Publication: Journal of Geophysical Research
Volume: 98
Issue: E11
ISSN: 0148-0227
Subject Category
Lunar And Planetary Exploration
Distribution Limits
No Preview Available