CryoSat

CryoSat was an ESA satellite that was destroyed on launch October 8, 2005 when the second stage engine of a modified Russian SS-19 ICBM did not cut-off as planned. CryoSat was proposed in 1998 by Duncan Wingham of University College London. The satellite's planned three year mission was to survey natural and human driven changes in the cryosphere on Earth. It was designed to provide much more accurate data on the rate of change of the surface elevation of the polar ice sheets and sea ice thickness. It was the first ESA Earth Sciences satellite selected through open, scientific competition.

CryoSat was to have been operated from the European Space Operations Centre (ESOC) in Darmstadt, Germany.

Description

CryoSat's primary instrument was SIRAL (SAR / Interferometric Radar Altimeter). SIRAL would operate 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 would have been combined (synthetic aperture processing) to reduce the surface footprint so that CryoSat could map smaller ice floes. CryoSat's most advanced mode would have been used around the ice sheet margins and over mountain glaciers. Here, the altimeter would have performed synthetic aperture processing and used a second antenna as an interferometer to determine the across-track angle to the earliest radar return. This would have provided the exact surface location being measured when the surface is sloping.

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

The ERS-1 and ERS-2 satellites were precursors that tested the techniques used by CryoSat.

Launch failure

CryoSat was launched from the Plesetsk Cosmodrome in Russia, using a Rockot launcher. (Rockot is a modified SS-19 rocket which was originally an ICBM designed to deliver nuclear weapons, but which Russia is now eliminating in accordance with the START treaties.) According to Mr. Yuri Bakhvalov, First Deputy Director General of the Khrunichev Space Centre, when the automatic command to switch off the second stage engine did not take effect, the second stage continued to operate until it ran out of fuel and as a consequence the planned separation of the third (Breeze-KM) stage of the rocket which carried the CryoSat satellite did not take place, and would thus have remained attached to the second stage. The upper rocket stages, together with the satellite, probably crashed in the Lincoln Sea.

Analysis of the error revealed that it was caused by faults in the programming of the rocket, which had not been detected in simulations.

CryoSat-2

After the launch failure of CryoSat, ESA immediately started to plan a replacement CryoSat mission. This included securing the industrial team which had built the original, ordering parts which have a long delivery time and establishing a funding scheme within existing budgets. Due to the importance of the scientific goals of this satellite, there was enormous support for this, and the initial phases for CryoSat-2 were approved when ESA's Earth Observation Programme Board agreed to build a copy of the spacecraft on February 23, 2006.

The new satellite was planned for launch in March 2009, just 3 years after the go-ahead to re-build. Although largely the same as the original satellite a number of key improvements were included. 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 September 2009, the launch is planned for February 28th, 2010.

See also

• Gravity Recovery and Climate Experiment (GRACE) NASA - launch 2002
• ICESat NASA - launch 2003

• Soil Moisture and Ocean Salinity satellite (SMOS) ESA - launch 2009
• Gravity Field and Steady-State Ocean Circulation Explorer (GOCE) ESA - launch 2009
• Atmospheric Dynamics Mission - Aeolus (ADM-Aeolus) ESA - launch 2010

External links

• Cryosat rocket fault laid bare
• CryoSat pages at ESA
• CryoSat-2 page at ESA Spacecraft Operations
• "Ice mission almost set for launch" – By Helen Briggs, BBC News, 22 July 2005
• Why did Cryosat crash? Australian Broadcasting Company's The Lab Cryosat story
• Cryosat-2: Scientists and Polar Explorers Collect Vital Support Data.
• Nature article The salt flat with curious curves says "the salt flat is also being used for Envisat, a European satellite, and could be used to calibrate future orbiters such as Cryosat-2"