Impact of terrestrial reference frame realizations on altimetry
satellites orbit quality, global and regional sea level trends: case
ITRF2014 versus ITRF2008
Authors: Rudenko Sergei , Esselborn Saskia , Schöne Tilo , Dettmering Denise 
Published: July 2018

Abstract. A terrestrial reference frame (TRF) is a basis for precise orbit determination of Earth orbiting satellites, since it defines positions and velocities of stations tracking data of which is used to derive satellite positions. In this paper, we investigate the impact of the International Terrestrial Reference Frame realization ITRF2014, as compared to its predecessor ITRF2008, on the quality of orbits, namely, on root-mean-square (RMS) fits of observations and orbital arc overlaps of three altimetry satellites (TOPEX/Poseidon, Jason-1 and Jason-2) at the time interval from August 1992 till April 2015 and on altimetry products computed using these orbits, such as single-satellite altimeter crossover differences, radial and geographically correlated mean sea surface height (SSH) errors, regional and global mean sea level trends. The satellite orbits are computed using Satellite Laser Ranging (SLR) and Doppler Orbitography and Radiopositioning Integrated by Satellite (DORIS) observations of a global network of stations. We have found that using ITRF2014 generally improves orbit quality, as compared to using ITRF2008. Thus, the mean values of the RMS fits of SLR observations decreased (improved) by 2.4 and 8.8 % for Jason-1 and Jason-2, respectively, but are almost not impacted for TOPEX/Poseidon, when using ITRF2014 instead of ITRF2008. The internal orbit consistency in the radial direction (as derived from arc overlaps) is reduced (improved) by 6.6 %, 2.3 %, and 5.9 % for TOPEX/Poseidon, Jason-1, and Jason-2, respectively. Single satellite altimetry crossover analysis indicates reduction (improvement) of the absolute mean crossover differences by 0.2 mm (8.1 %) for TOPEX/Poseidon, 0.4 mm (17.7 %) for Jason-1 and 0.6 mm (30.9 %) for Jason-2 with ITRF2014 instead of ITRF2008. The major improvement of the mean values of the RMS of crossover differences (0.13 mm (0.3 %)) has been found for Jason-2. Multi-mission crossover analysis shows slight improvements in the standard deviations of radial errors: 0.1 %, 0.2 % and 1.6 % for TOPEX/Poseidon, Jason-1 and Jason-2, respectively. The standard deviations of geographically correlated mean SSH errors improved by 1.1 % for Jason-1 and 5.4 % for Jason-2 and degraded by 1.3 % for TOPEX/Poseidon. The change from ITRF2008 to ITRF2014 orbits has only minor effects on the estimation of regional and global sea level trends over the 22 years time series from 1993 to 2015. However, on interannual time scales (3–8 years) large scale coherent trend patterns are observed that seem to be connected to drifts between the origins of the tracking stations networks. This leads to uncertainties of interannual global mean sea level of up to 0.06 mm yr−1 for TOPEX/Poseidon, 0.05 mm yr−1 for Jason-1, and up to 0.12 mm yr−1 for Jason-2. The respective changes of regional sea level trend on these time scales reach maximum values of 0.4 mm yr−1 for TOPEX/Poseidon, of 0.5 mm yr−1 for Jason-1 and of 1.0 mm yr−1 for Jason-2.