Positioning of the French transportable laser ranging system (FTLRS) in Corsica over the 2002 and 2005 campaigns
Gourine, Bachir ... [et al.]
The geodetic site of Ajaccio in Corsica is the main calibration site of satellite altimeters in the Mediterranean area. It has been developed for oceanographic missions such as TOPEX/Poseidon (T/P, 1992), Jason-1 (2001) and Envisat (2002). The French Transportable Laser Ranging System (FTLRS) can be deployed there during an absolute calibration campaign. The role of the FTLRS is to provide accurate tracking (range measurements) of the spacecraft altitude when passing above the in situ instruments (tide gauges, notably) and, at the same time, to ensure an absolute geocentric positioning to be tied to the tide gauge reference points. The first absolute calibration campaign has been carried out in Ajaccio, from January to September 2002; a second one has been carried out from May to October 2005. The goal is to detect a possible drift in the altimeter bias that could be detected at the 1 mm/yr level, or less if possible, between this two periods. To detect such a drift however, we have to be confident in the positioning of the sea surface height by in situ instruments at least at the same level of accuracy. Here, we present the computation of the two sets of geocentric coordinates from the FTLRS range data acquired in 2002 and in 2005 mainly on the low Earth geodetic satellites Starlette and Stella. The paper describes the different steps of the processing, notably in order to avoid correlations between the FTLRS range bias, the coordinates and the expected accuracy of computed orbits. Finally, a few mm accuracy is reached for the double positioning of the FTLRS in 2002 and in 2005. The tectonic velocity being deduced from both set of coordinates is compared to GPS permanent measurements to the level of less than 1 mm/yr
Event: XXIII International FIG Congress : Shaping the change
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