Calibration and validation of satellite radar altimeters: field studies on the Greenland Ice Cap

Abstract

The original aim of this proposal followed on from the aims of previous related work (NERC GEF loan 766 Nienow) on the Greenland Ice Sheet to help improve the estimates of elevation change of land-ice and sea-ice as determined from the European Space Agency’s CryoSat radar altimeter. In February 2006 the European Space Agency (ESA) confirmed that CryoSat2 would be built to replace the loss of CryoSat following launch failure on 8th October 2005 and so planned ground based calibration activities in spring 2006 continued. One of the goals of the CryoSat mission is to "reduce the uncertainty in the ice sheet contribution to sea level to a magnitude similar to that associated with other sources of sea level rise". The goal is being pursued via repeat measurements of the mass and thickness of ice masses by radar altimetry. A key part of the mission is a field calibration/validation program designed to provide rigorous estimates of the uncertainty of airborne and satellite radar measurements over land and sea ice. This fieldwork program is part-funded through the NERC Consortium bid, “Validation and Provision of CryoSat Measurements of Fluctuations of the Earth’s Land and Marine Ice Fluxes” (NER/0/5/2003/00620, P.I. Prof. D. Wingham, co-I’s include P. Nienow, D. Mair and E. Morris). Part of the field activity required additional equipment to ensure a successful calibration program. This equipment was provided by NERC GEF in the form of differential GPS equipment that was essential for determining the uncertainty of the radar measurements and thus, the overall accuracy and likely effectiveness of satellite radar altimeter missions.