Cross-calibration of TOPEX/Poseidon, ERS-2 and GEOSAT altimetry Original Research Article

Long-term monitoring of the NASA (TOPEX) altimeter bias drift onboard TOPEX/Poseidon has been undertaken by comparison against in-situ tide gauge data and used as a benchmark for cross-calibration of the concurrent altimeter mission ERS-2 and of the earlier GEOSAT mission. Dual crossovers between ERS-2 and TOPEX/Poseidon provide a measure of the relative bias along with other parameters defining differences between the altimetric data sets. Attempts to link GEOSAT with the missions in the 1990s have relied on tide gauge time series with the assumption that geographically correlated errors in GEOSAT have zero effect. In this study we utilise GEOSAT crossovers and tide gauge enhanced altimetry between TOPEX/Poseidon and GEOSAT to estimate a 1 cy/rev correction simultaneously with the relative altimeter bias. Evidence of improvement is shown by comparison of the GEOSAT altimetry against the EGM96 mean sea-level.