CryoSat mission overview
CryoSat-2 carries a sophisticated radar altimeter to meet two principal challenges.
The first is to acquire accurate measurements of the thickness of floating sea ice so that annual variations can be detected. The second is to survey the surface of ice sheets accurately enough to detect small changes.
CryoSat-2's radar altimeter is based on heritage from existing instruments, but with several major enhancements designed to improve measurements of icy surfaces. Because of its operations in SAR and Interferometric modes, the altimeter is called SIRAL (SAR Interferometric Radar Altimeter). CryoSat-2 is orbiting Earth at an unusually high inclination, reaching latitudes of 88° north and south.
CryoSat-2 will determine the thickness of floating sea ice by measuring the freeboard of ice floes; that is the height by which the ice extends above the water surface. This technique has been demonstrated with the ERS-1 radar altimeter, but this instrument, as with all conventional radar altimeters, is hampered by its relatively low spatial resolution of about 5 km. CryoSat-2 will achieve improved spatial resolution of 250 m in the along-track direction using the Synthetic Aperture technique.
The first returning energy in the radar echo comes from the part of the Earth's surface closest to the satellite. Over sea ice (and ocean) this point is directly below the satellite, but on sloping surfaces, such as those found around the edges of ice sheets, this nearest point can be anywhere.
CryoSat-2 is able to pin down the location of the echo in the fore- and aft-direction by using its SAR capability, but to resolve left and right an additional feature is needed. Over these sloping surfaces CryoSat-2 operates in the SAR-Interferometry mode, which provides the key measurements of the angle of arrival and thus the pin-pointed source of the echo.
|CryoSat -2 overview|
|Launched||8 April 2010|
|Mission duration||Minimum 3 years|
|Orbit||LEO, non Sun-synchronous|
|- Altitude||717 km|
|- Inclination||92 deg|
|- Repeat cycles||369 days with 30 day sub-cycle|
|Payload||SIRAL (SAR/Interferometric Radar Altimeter)|
|Mass||720 kg (incl 37 kg fuel)|
|Dimensions||4.60 x 2.4 x 2.2 m|
|Launch provider||International Space Company Kosmotras|
|Launcher||Russian/Ukrainian Dnepr based on SS-18 intercontinental ballistic missile|
Last update: 6 November 2013