P34A-07
Mars Gravity Field and Upper Atmosphere from MGS, Mars Odyssey, and MRO

Wednesday, 16 December 2015: 17:21
2011 (Moscone West)
Antonio Genova1, Sander J Goossens2, Frank G Lemoine3, Erwan Mazarico4, Gregory A Neumann5, David E Smith1 and Maria T Zuber6, (1)Massachusetts Institute of Technology, Cambridge, MA, United States, (2)University of Maryland Baltimore County, Baltimore, MD, United States, (3)NASA Goddard SFC, Greenbelt, MD, United States, (4)NASA Goddard Space Flight Center, Greenbelt, MD, United States, (5)NASA, Baltimore, MD, United States, (6)Massachusetts Inst Tech, Cambridge, MA, United States
Abstract:
The NASA orbital missions Mars Global Surveyor (MGS), Mars Odyssey (ODY), and Mars Reconnaissance Orbiter (MRO) have been exploring and monitoring the planet Mars since 1997. MGS executed its mapping mission between 1999 and 2006 in a frozen sun-synchronous, near-circular, polar orbit with the periapsis altitude at ~370 km and the dayside equatorial crossing at 2 pm Local Solar Time (LST). The spacecraft was equipped with onboard instrumentation to acquire radio science data and to measure spacecraft ranges to the Martian surface (Mars Orbiter Laser Altimeter). These measurements resulted in static and time-varying gravity field and high-resolution global topography of the planet.

ODY and MRO are still orbiting about Mars in two different sun-synchronous orbits, providing radio tracking data that indirectly measure both the static and time-varying gravity field and the atmospheric density. The orbit of ODY has its periapsis at ~390 km altitude and descending node at 4-5 pm LST. However, the spacecraft also collected measurements at lower altitudes (~220 km) in 2002 prior to the mapping phase. Since November 2006, MRO is in a low-altitude orbit with a periapsis altitude of 255 km and descending node at 3 pm LST. Radio data from MRO help improve the resolution of the static gravity field and measure the mass distribution of the polar caps, but the atmospheric drag at those altitudes may limit the benefits of these radio tracking observations.

We present a combined solution of the Martian gravity field to degree and order 110 and atmospheric density profiles with radio tracking data from MGS, ODY and MRO. The gravity field solution is combined with the MOLA topography yielding an updated map of Mars crustal thickness. We also show our solution of the Love number k2 and time-variable gravity zonal harmonics (C20 and C30, in particular). The recovered atmospheric density profiles may be used in atmospheric models to constrain the long-term variability of the constituents in the upper atmosphere.

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