HR: 0800h
AN: G31C-0804    [Abstracts]
TI: Effects of GRACE orbit decay on the gravity field recovery
AU: * Yamamoto, K
EM: yamamoto@kugi.kyoto-u.ac.jp
AF: Department of Geophysics, Graduate School of Science, Kyoto University, Kitashirakawa Oiwake-cho, Sakyo-ku, Kyoto, 606-8502 Japan
AU: Otsubo, T
EM: otsubo@nict.go.jp
AF: National Institute of Information and Communications Technology, 893-1 Hirai, Kashima, 314-0012 Japan
AU: Kubo-oka, T
EM: tkubooka@nict.go.jp
AF: National Institute of Information and Communications Technology, 893-1 Hirai, Kashima, 314-0012 Japan
AU: Fukuda, Y
EM: fukuda@kugi.kyoto-u.ac.jp
AF: Department of Geophysics, Graduate School of Science, Kyoto University, Kitashirakawa Oiwake-cho, Sakyo-ku, Kyoto, 606-8502 Japan
AB: Effects of satellite ground track changes of GRACE on monthly gravity field recoveries are investigated. Although GRACE provides monthly gravity field solutions through out the mission lifetime, it may not maintain to keep the same orbit due to the thruster fuel limitation. It causes temporal variation of ground tracks. Globally uniform ground tracks provide a preferable condition for the solutions, however large gaps in the ground tracks may be appeared at some specific orbit altitude. In case of a gravity field recovery using relatively short period of a month or so, the variation of ground tracks affects the precision of the gravity field solutions. It is a serious problem when the solutions are employed for detecting temporally gravity changes which are at almost detection limits. In this study, the recoveries of four-weekly gravity fields are simulated and the relation between the recovery precision and the ground track is investigated. The result shows that the GRACE ground track of year 2003 was in good condition for four-weekly gravity field recovery, but it will sometimes appear worse cases as the decay of orbit altitude. In those cases, the global standard deviations of geoid height errors will be about 4 times worse than the best case. We discuss a preferable temporal resolution in order to suppress such difference of the recovery precision per time period and to obtain the solutions of temporally homogeneous quality. A method to correct the large error solutions using ones in other periods is also discussed.
DE: 6062 Satellites
DE: 3010 Gravity
DE: 1200 GEODESY AND GRAVITY
DE: 1241 Satellite orbits
SC: Geodesy [G]
MN: 2004 AGU Fall Meeting