SHORT-ARC CALIBRATION OF THE TOPEX POSEIDON AND ERS-1 ALTIMETERS UTILIZING IN-SITU DATA/

A calibration of the TOPEX/POSEIDON and ERS 1 altimeters has been unde rtaken using altimetry across the English Channel. Data from the tide gauge installed at Newhaven and the satellite laser ranger at Herstmon ceux were used in conjunction with local models for the geoid, ocean t ide, and storm surge to generate bias values at each subsatellite alti metry point. A range bias value of -17.3 cm was generated for the NASA TOPEX altimeter relative to the four-parameter sea state bias model c alculated by Gaspar et al. [1994]. The corresponding value for the Cen tre National d'Etudes Spatiales (CNES) POSEIDON solid state altimeter was -0.3 cm. The impact of other parameterizations for the sea state b ias on the altimeter bias is studied. The derived results are in close agreement with results from the NASA calibration campaign at Harvest oil platform near California and the CNES experiment at the Italian La mpedusa island. The bias derived for ERS 1 was -39.3 cm relative to an Aston-derived single-parameter sea state bias model.