DORIS Time Bias estimated using Jason-1, TOPEX/POSEIDON, and ENVISAT orbits
Mr Nikita ZELENSKY(1), Dr Jean-Paul BERTHIAS(2), Dr Frank LEMOINE(3)
(1) sgt, greenbelt, maryland, usa
Session theme: POD
DORIS is a globally distributed, all-weather system providing near continuous precise Doppler tracking of TOPEX/POSEIDON (T/P), Jason-1, ENVISAT, and other satellites. The DORIS system which has been critical in establishing the high precision orbit determination standards now enjoyed by these missions, continues to evolve and improve. There is a small discrepancy between the DORIS time tag computed by CNES using the DORIS timing data, and a time tag estimated using DORIS range-rate data with respect to orbits referencing SLR or GPS time. This discrepancy is evaluated using DORIS time biases estimated over T/P, Jason-1, and ENVISAT orbits which reference SLR or GPS time. For T/P, Jason-1 and ENVISAT in 2002, this DORIS time bias amounts to 6 to 7 microseconds. Over the span of the T/P mission, this time bias has ranged from +17 to 20 microseconds. This paper addresses the precision and nature of the estimated time biases by evaluating such estimates over orbits computed with various gravity fields, computed using SLR/DORIS and GPS tracking, and computed by GSFC, JPL, and CNES analysis centers.
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