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Calibration of ERS-2, TOPEX/Poseidon and Jason-1 Microwave Radiometers using GPS and Cold Ocean Brightness Temperatures

Lookup NU author(s): Professor Philip Moore, Professor Stuart Edwards


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Sea-level change studies from altimetric satellites are reliant on range stability of the sea-surface heights computed from the orbital positioning and geophysically corrected data. One such correction, namely the wet tropospheric delay induced by the highly variable atmospheric water vapour content, is provided by radiometers onboard ERS-2, TOPEX/Poseidon and its follow on mission Jason-1. In this study the long term stability of ERS-2 and TOPEX radiometers are investigated together with radiometer performance to date of Jason-1. Each of the three microwave radiometers is investigated with observed drift in the brightness temperatures approximated by reference to the coldest tempertures over the oceans. For example the TOPEX radiometer investigations show that the dominant drift is about 0.2 k/year in the 18GHz channel over the first 7-8 years stablising and even decreasing slightly thereafter. In contrast, the 21GHz and 37GHz channels are comparitively stable. Utilising correc6tion formulae a modified wet tropospheric range is inferred from 'small-change' analysis of the radiometric correction given on the altimetric Geophysical Data Records. This investigation undertakes the validation of the accuracy of this formulism by independant comparison against GPS derived wet tropospheric delays inferred at 14 coastal IGS stations with neat continuous data from Sept. 1992 through to the present day. Early comparison between GPS results and ERS-2 and TOPEX shows the ERS-2 radiometer measuring ~14mm long. Additionally for TOPEX, the altimetric range stability is revisited by comparison against time series from the global network of tide gauges.

Publication metadata

Author(s): Moore P, Edwards SJ

Publication type: Conference Proceedings (inc. Abstract)

Publication status: Unknown

Conference Name: 15 Years of Progress in Radar Altimetry

Year of Conference: 2006