HR: 11:35h
AN: G32A-05    [Abstracts]
TI: Improving the Determination of the Terrestrial Reference Frame Using New SLR Satellites
AU: * Ries, J C
EM: ries@csr.utexas.edu
AF: Center for Space Research, 3925 W. Braker Lane, Suite 200, Austin, TX 78759 United States
AB: Future requirements for the Terrestrial Reference Frame (TRF) are likely to be about an order of magnitude more accurate than currently being achieved. These requirements arise from the need for ensuring that the temporal changes we observe in the Earth system, such as global mean sea level, sea surface topography changes, crustal deformation and gravity changes due to mass transport, are real geophysical signals and not artifacts of the measurement system. Considerable investment in the improvement and deployment of the ground components of the geodetic network is going to be required to achieve this, but the space components may also need to be considered. In particular, the definition of the origin for the TRF is critically dependent on satellite laser ranging (SLR) to a few large, high-altitude geodetic satellites. The size of these satellites leads to significant uncertainty in the calculation of the center of mass offset correction, which is now the largest source of uncertainty in the determination of the Earth's gravitational coefficient (GM). Their high altitude makes it difficult for some lower power ranging systems to acquire data, particularly during daylight. This high altitude was originally necessary to ensure that the errors in the available models for the Earth's gravity field were greatly attenuated, but, with the advent of gravity models from the Gravity Recover and Climate Experiment (GRACE), the longer wavelength gravity model errors have been reduced by orders of magnitude. As a result, it is likely that geodetic satellites at a lower altitude (but still well above any significant drag effect) can provide a stronger and more accurate contribution to the TRF origin determination. Being lower, the dynamical tie to the Earth's center of mass will be stronger, and a shorter orbital period will provide more ranging opportunities. These lower altitude satellites can also be made smaller, supporting more accurate calculations of the center of mass offset correction and leading to increased accuracy in the determination of GM and the reference frame scale. This paper presents the results of a preliminary analysis to test the benefit to the reference frame determination from adding new geodetic SLR satellites.
DE: 1225 Global change from geodesy (1222, 1622, 1630, 1641, 1645, 4556)
DE: 1229 Reference systems
DE: 1294 Instruments and techniques
SC: Geodesy [G]
MN: Fall Meeting 2005