NTRS - NASA Technical Reports Server

Advisory – Planned Maintenance: On Monday, July 15 at 9 PM Eastern the STI Compliance and Distribution Services will be performing planned maintenance on the STI Repository (NTRS) for approximately one hour. During this time users will not be able to access the STI Repository (NTRS).

Back to Results
An improved gravity model for Mars: Goddard Mars Model-1 (GMM-1)Doppler tracking data of three orbiting spacecraft have been reanalyzed to develop a new gravitational field model for the planet Mars, GMM-1 (Goddard Mars Model-1). This model employs nearly all available data, consisting of approximately 1100 days of S-bank 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 optimum 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, near-polar orbiting Mars Observer spacecraft should provide a significant improvement over GMM-1, particularly at high latitudes where current data poorly resolves the gravitational signature of the planet.
Document ID
Acquisition Source
Legacy CDMS
Document Type
Technical Memorandum (TM)
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, Inc. Lanham, MD., United States)
Fricke, S. K.
(RMS Technologies, Inc. Landover, MD., United States)
Lemoine, F. G.
(Colorado Univ. Boulder., United States)
Date Acquired
September 6, 2013
Publication Date
May 1, 1993
Subject Category
Report/Patent Number
NAS 1.15:104584
Accession Number
Distribution Limits
Work of the US Gov. Public Use Permitted.
No Preview Available