CoAuthors

Denise Dettmering (DGFI-TUM, Germany); Mathis Bloßfeld (DGFI-TUM, Germany); Saskia Esselborn (GFZ, Germany); Tilo Schöne (GFZ, Germany)

Starting with ERS-1 and TOPEX/Poseidon in 1992 the altimeter record has reached already 25 years. Since orbits of altimeter satellites are a prerequisite for sea level investigations and since any radial error directly maps in sea level derived in satellite altimetry, long-term stability of orbits of altimeter satellites is very important, especially for investigation of long-term effects, such as global and regional mean sea level changes as well as acceleration of global mean sea level. Therefore, it is important to derive satellite orbits in the same up-to-date reliable reference frame using up-to-date models for precise orbit determination. To fulfil this, a series of reprocessing of altimetry satellite orbits has been undertaken by space agencies in the recent decade, for example, within the “Reprocessing Altimeter Products for ERS” and “Climate Change Initiative Sea Level” project funded by the European Space Agency (ESA).

In this presentation, we review some effects on the long-term stability of orbits of altimetry satellites. In particular, we show the influence of time variable models of the Earth’s gravity field on regional mean sea level. We show also the impact of high-frequency non-tidal Earth’s mass changes provided by Atmospheric and Oceanic De-aliasing Level-1B products on the geographically correlated errors of five altimetry missions. We show the impact of latest Terrestrial Reference Frame realizations (ITRF2014, DTRF2014 and JTRF2014) on the orbit of Jason-2, as compared to the previous realization (ITRF2008) and its extension for SLR and DORIS stations (SLRF2008 and DPOD2008). Importance of modelling non-tidal (atmospheric and oceanic) loading for precise orbit determination of altimetry satellites is also illustrated.