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ESA's new range of radar altimeters for the extraction of geophysical parameters from land, sea ice and ocean surfaces

Robert Cullen(1) , Robert L. Hawley(2) , Wolfgang Rack(3) , Christian Hass(3) , Duncan Wingham(4) , Malcolm Davidson(1) , and Constantin Mavrocordatos(1)

(1) ESA, ESTEC, 2200 AG Noordwijk, Netherlands
(2) University of Cambridge, Lensfield Road, Cambridge, CB2 1ER, United Kingdom
(3) Alfred Wegener Institute for Polar and Marine Research, Postfach 12 0161, 27515 Bremerhaven, Germany
(4) University College London, Gower Street, London WC1E 6BT, United Kingdom


Despite the loss of CryoSat, ESA's first Earth opportunity mission, during its launch sequence in Oct 2005, ESA have been fortunate enough to have acquired, processed to Level 1b and analysed a significant amount of campaign data from ESA's aircraft bourne radar altimeter (ASIRAS) designed to have similar functionality to CryoSat's Synthetic Interferometric Radar Altimeter (SIRAL). This data acquisition took place for the original purpose of validating CryoSat retrievals.

Our initial analyses of the level 1b data have revealed some very interesting results both over land and sea ice test sites from respective campaigns conducted in the Arctic during the land-ice spring/autumn campaigns of 2004 and for sea-ice in the Bay of Bothnia during March 2005. Since a further ASIRAS campaign in the Arctic is guaranteed for April/May 2006 we look at how this data can be exploited in view of future ESA Earth observation radar altimeter missions. Verification of the ASIRAS data with coincident laser altimeter and in-situ data collected at test sites is also presented.

One of the challenges of European Space Agency's new breed of radar altimeters is that they exploit echo phase in a far more complex manner that previous pulse-width limited counterparts (EnviSat RA-2 and ERS-1/2 RA, for example). We explain how the instrument level 0 data is processed to level 1b and we further describe the necessity to take a new approach to calibration requiring correction for a new range of instrument based phase errors alongside the usual range, gain and instrument filter corrections.


Full paper

Workshop poster


                 Last modified: 07.10.03