HR: 0800h
AN: G51A-0805    [Abstracts]
TI: Measurement of the Martian upper atmospheric density using Mars Odyssey radio tracking data
AU: * Mazarico, E
EM: mazarico@mit.edu
AF: Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, 77, Massachusetts Avenue, Cambridge, MA 02139 United States
AU: Zuber, M T
EM: zuber@mit.edu
AF: Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, 77, Massachusetts Avenue, Cambridge, MA 02139 United States
AU: Zuber, M T
EM: zuber@mit.edu
AF: NASA Goddard Space Flight Center, Laboratory for Terrestrial Physics, NASA Goddard Space Flight Center, Greenbelt, MD 20771 United States
AU: Lemoine, F G
EM: Frank.Lemoine@gsfc.nasa.gov
AF: NASA Goddard Space Flight Center, Space Geodesy BranchCode 926, NASA Goddard Space Flight Center, Greenbelt, MD 20770 United States
AU: Smith, D E
EM: David.E.Smith@nasa.gov
AF: NASA Goddard Space Flight Center, Laboratory for Terrestrial Physics, NASA Goddard Space Flight Center, Greenbelt, MD 20771 United States
AB: We present measurements of the Martian atmospheric density at ~400km altitude. We used radio tracking data to perform Precision Orbit Determination on the Mars Odyssey spacecraft, between March 2002 and November 2004. Usually limited to gravity investigations, we show it is possible to use this technique to estimate the atmospheric density of the upper atmosphere. The recent improvements in the a priori physical models used (such as the high-resolution gravity field of Mars obtained by the Mars Global Surveyor) enable us to isolate the contribution of the atmospheric drag from the various forces acting on the spacecraft. We adjusted model parameters on many spacecraft trajectory segments ('arcs'), including time biases for each tracking station, thruster firings, atmospheric drag coefficient (CD) and solar radiation coefficient (CR). Except for a few arcs that gave anomalous CD or CR, we obtain results that are consistent from arc to arc, and are indicative of robust and meaningful results. Combined with model-derived densities, we obtain a times series of the measured density, lower than the atmospheric model (based on the Stewart 1987 model), indicative of a thinner upper atmosphere and a greater scale height in that region. Also, we find that the solar input has a major influence on the upper atmosphere, as predicted by the model, but that the seasonal variations are not as strong.
DE: 0328 Exosphere
DE: 1220 Atmosphere monitoring with geodetic techniques (6952)
DE: 6952 Radar atmospheric physics (1220)
DE: 6999 General or miscellaneous
SC: Geodesy [G]
MN: Fall Meeting 2005