HR: 16:15h
AN: P44A-02    [Abstracts]
TI: Improvements in Lunar Topographic Knowledge From Laser Altimetry and Tracking
AU: * Neumann, G A
EM: neumann@tharsis.gsfc.nasa.gov
AF: NASA Goddard Space Flight Center, Code 698, Greenbelt, MD 20771, United States
AU: Smith, D E
EM: dsmith@tharsis.gsfc.nasa.gov
AF: NASA Goddard Space Flight Center, Code 698, Greenbelt, MD 20771, United States
AU: Lemoine, F G
EM: flemoine@puuoo.gsfc.nasa.gov
AF: NASA Goddard Space Flight Center, Code 698, Greenbelt, MD 20771, United States
AU: Zuber, M T
EM: zuber@mit.edu
AF: Massachusetts Institute of Technology, Dept of Earth, Atmospheric and Planetary, Cambridge, MA 02139, United States
AB: The next few years will see 4 laser altimeters in lunar orbit, for the first time since the Clementine Mission in 1994. Any one of these altimeters will make a significant improvement in our knowledge of the lunar topography but the combined datasets can be expected to revolutionize our understanding of the moon's shape, how it was formed, the processes involved, and its solar illumination. All the missions are nominally in polar orbit ensuring that almost every part of the lunar surface within approximately 10 degrees of the poles, beyond the reach of the Clementine lidar, will be saturated with altimeter measurements. Typically the altimeters will generate 12 orbital profiles per day and will map ~one degree of longitude on each ascending pass. The extensiveness of the coverage will depend not only on the performance of the instruments but also on the duration of each mission, with each ground track improving the coverage density. Gravity fields will benefit from additional coverage and novel tracking systems, which should improve orbital accuracy that will complement the meters-or-less ranging accuracy of these instruments. When tied to the same reference system and selenopotential model, observational and orbital errors and discrepancies between the missions will be identified and corrected to produce a complete topographic model with a horizontal accuracy globally of tens of meters and a radial accuracy of ~one meter. Particularly on the far side, images and other datasets, previously uncertain by many kilometers, may be precisely registered to this model. The vast quantity of data will enable the determination of areas of full and partial shadow at the poles and the hours of illumination at locations of "eternal light". Knowledge of the rotation of the moon over the last many millions of years will permit us to extrapolate into the past the lighting and shadow conditions that are necessary for the formation of near surface deposits of volatile elements.
DE: 1243 Space geodetic surveys
DE: 1294 Instruments and techniques
DE: 5417 Gravitational fields (1221)
SC: Planetary Sciences [P]
MN: 2007 Fall Meeting