Station-dependent SLR correction improves the TOPEX/Poseidon altimetry satellite orbit
TOPEX/Poseidon (T/P) was one of the first major altimetry satellite missions. It was operational between 1992 and 2006 and serves as the reference mission for its successors in the Jason and Sentinel-6 series. As such, it is of great importance for studies of global and regional sea level change, ocean circulation, and climate phenomena such as El Niño. With a diameter of over 160 cm, its Laser Retroreflector Array (LRA), the on-board target for Satellite Laser Ranging (SLR) measurements, is not ideally designed for centimeter orbit accuracies. The resulting large phase center fluctuations are a major limiting factor for precise orbit determination of T/P and thus for ocean surface surveys.
Scientists of DGFI-TUM have developed a correction function for SLR observations that resolves LRA-related phase center variations as well as effects that depend on satellite and observing station, such as range biases. The function uses the viewing angles of the observation to determine a correction value that is added to the SLR distance measurement. Since the function is continuous, interpolation between tabulated values is not required and interpolation errors are avoided. The correction reduces the root mean square (RMS) of the SLR observation residuals (observed - computed) for the entire T/P mission from 33.78 cm to 1.97 cm (1.59 cm for SLR core stations). Details can be found in the article Station-dependent satellite laser ranging measurement corrections for TOPEX/Poseidon (Advances in Space Research, 2023, DOI: 10.1016/j.asr.2022.09.002). The station-dependent correction parameters are published as a supplement to the article, so that the measurement correction can be implemented in any precise orbit determination software.
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