Assessment of ITRF2014 for precise orbit determination of altimetry satellites
Event: 2016 IDS Workshop
Session: IDS processing for and with ITRF2014
Presentation type: Type Oral
A terrestrial reference frame (TRF) is a basis for precise orbit determination of Earth orbiting satellites. New GFZ VER13 precise orbits of altimetry satellites ERS-1 (1991-1996), ERS-2 (1995-2003), TOPEX/Poseidon (1992-2005), Envisat (2002-2012), Jason-1 (2002-2013) and Jason-2 (2008-2015) have been derived at the time intervals given in the ITRF2014 terrestrial reference frame realization by adding the information on the stations missing in the ITRF2014 from DPOD2008 and SLRF2008, since no DPOD2014 and SLRF2014 are available yet. This allows using the same set of stations for precise orbit determination. The orbits are computed using satellite laser ranging (SLR) data and single satellite altimeter crossover differences for ERS-1, by using additionally PRARE (Precise Range and Range-rate Equipment) data for ERS-2. SLR and DORIS (Doppler Orbitography and Radiopositioning Integrated by Satellite) measurements have been used to derive orbits of four other satellites. The Cartesian X, Y, Z coordinates of PRARE stations used for precise orbit determination of ERS-2 were estimated at each orbital arc, since they are missing in the ITRF. The quality of GFZ VER13 orbits is compared with the quality of GFZ VER11 (2015) orbits derived using the same up-to-date background models for precise orbit determination, but using a previous ITRF realization, namely, ITRF2008. We have found that using ITRF2014 generally improves orbit quality, as compared to using ITRF2008. Thus, the mean values of the root-mean-square (RMS) fits of SLR observations reduced (improved) by 1.8, 3.1, 2.4 and 8.8% for ERS-2, Envisat, Jason-1 and Jason-2, respectively, and are almost not impacted for ERS-1 and TOPEX/Poseidon, when using ITRF2014 instead of ITRF2008. The internal orbit consistency in the radial direction being important for altimetric applications and being characterized by the satellite position differences in this direction at two-day arc overlaps reduced (improved) by 0.4, 0.6, 2.4, 5.1 and 7.1% for ERS-2, ERS-1, Jason-1, Jason-2 and TOPEX/Poseidon, but slightly (by 0.7%) increased for Envisat. We provide also the results of the single-satellite altimetry crossover analysis of VER13 orbits, as compared to VER11 orbits, investigate scatter and frequencies of radial errors and geographically correlated errors obtained using new orbits, and show the impact of the ITRF realizations used on the radial orbit differences, sea level heights and sea level rates.