CryoSat

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CryoSat is an ESA satellite launched on 8 April 2010 . The satellite will monitor variations in the extent and thickness of polar ice. The information it provides about the behaviour of coastal glaciers that drain thinning ice sheets will be key to better predictions of future sea-level rise.

CryoSat is operated from the European Space Operations Centre (ESOC) in Darmstadt, Germany.

CryoSat's primary instrument is SIRAL (SAR / Interferometric Radar Altimeter). SIRAL operates in one of three modes, depending on where (above the Earth's surface) CryoSat was flying. Over the oceans and ice sheet interiors, CryoSat would have operated like a traditional radar altimeter. Over sea ice, coherently transmitted echoes are combined (synthetic aperture processing) to reduce the surface footprint so that CryoSat could map smaller ice floes. CryoSat's most advanced mode is used around the ice sheet margins and over mountain glaciers. Here, the altimeter performs synthetic aperture processing and uses a second antenna as an interferometer to determine the across-track angle to the earliest radar return. This provides the exact surface location being measured when the surface is sloping.

Although largely the same as the original satellite a number of key improvements were included in CryoSat-2. The most significant was the decision to provide a fully duplicated payload to enable the mission to continue if a fault caused the loss of the SIRAL radar, but there were many other changes "under the hood". Some of these were caused by obsolescence in the original design, some improved reliability and others made the satellite easier to operate. Despite all the changes the mission remains the same and the performance, in terms of measurement capability and accuracy, remains the same. As of 14 January 2010 (2010 -01-14)[update], the launch was scheduled for February 25, 2010 with a Dnepr rocket from the Baikonur Cosmodrome, but this was delayed. The CryoSat 2 launched on April 8, 2010 at 13:57 UTC.

For positioning purposes, CryoSat included a DORIS receiver, a laser retroreflector and three star trackers.

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