Detection an analysis of SLR station measurement biases
19/09/2016 | 17:45 | Session 2: Global gravity field modelling
Author(s): Franck Reinquin, Sean Bruinsma and Alexandre Couhert
Franck Reinquin, Sean Bruinsma and Alexandre Couhert
Satellite Laser Ranging (SLR) data, made available by the International Laser Ranging Service (ILRS), is essential to the accurate determination of the very-low degree coefficients of the gravity field. It is also essential to validate and quantify the orbit precision of the altimeter satellites. It is the only independent and unambiguous validation method that can provide the absolute radial orbit accuracy by means of high elevation passes. However, the accuracy of the data, even of some of the core stations, is irregular. Biases and drifts are observed in the ranging data. The SLR data are considered unbiased in the altimeter satellites’ orbit validation process (i.e., range or time bias are not estimated). As a consequence, unknown or not communicated errors in the ranging data (note: the ILRS provides incomplete station error information) directly affect the validation results.
SLR station biases from 2001 to 2014 were estimated in precise orbit determinations on the geodetic satellites LAGEOS-1/2 (at 5900 km altitude) and Starlette/Stella (at about 850 km). ITRF2014 station coordinates were used in our most recent reprocessing. All advertized station corrections by the ILRS were applied in this computation. The estimated biases are compared with validation results of the same stations on Jason-1/2 and Cryosat-2 orbits. Finally, a more realistic external validation of the Jason-1/2 and Cryosat-2 orbits is obtained by taking the station biases into account.