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Gravity Field Mapping of Mars with MGSTracking of the MGS spacecraft in orbit at Mars by the Deep Space Network since last September has provided doppler and range measurements that are being used to improve the model of the Mars gravity field. During most of October 1997, April 1998, and June thru August 1998 high quality tracking data were obtained while the periapse was in the northern hemisphere at altitudes in the 170 to 190 km range. The eccentric orbit had a period of about 11.5 hrs and an inclination of about 96.2 degrees so that low altitude tracking was obtained over most of the northern hemisphere, including the north polar icecap. Data from the earlier Mariner 9 and Viking missions have been added to the MGS data and a series of experimental gravity models developed from the combined datasets. These models have generally been of degree and order 70 and are a significant improvement over earlier models that did not include the MGS data. Gravity anomalies over the north polar cap region of Mars are generally less than 50 to 100 mgals and show no obvious correlation with the topography. Successive MGS orbits derived using these new models are showing agreement at the 100 meter level, and this has been confirmed with the laser altimeter (MOLA) on MGS These comparisons are expected to improve significantly as more tracking data get included in the solution and the MGS orbit becomes more circular giving a more balanced geographical distribution of data at low altitude. This will happen early in 1999 as the orbit approaches the mapping configuration of a circular orbit at about 400 Km.
Document ID
19990115951
Acquisition Source
Goddard Space Flight Center
Document Type
Conference Paper
Authors
Smith, David E.
(NASA Goddard Space Flight Center Greenbelt, MD United States)
Zuber, Maria T.
(Massachusetts Inst. of Tech. Cambridge, MA United States)
Lemoine, Frank G.
(NASA Goddard Space Flight Center Greenbelt, MD United States)
Date Acquired
August 19, 2013
Publication Date
January 1, 1998
Subject Category
Lunar And Planetary Exploration
Meeting Information
Meeting: Fall AGU Meeting
Location: San Francisco, CA
Country: United States
Start Date: December 6, 1998
End Date: December 10, 1998
Sponsors: American Geophysical Union
Distribution Limits
Public
Copyright
Other

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