Paris — An airborne version of a new-generation radar sensor to be flown on Europe’s Cryosat-2 ice-monitoring Earth observation satellite will be tested this spring from Norway’s Svalbard Island near the North Pole. The test is intended to help mission managers in their preparations for integration of the actual radar payload into the satellite.
During the tests, an aircraft provided by the German Aerospace Center, DLR, will carry a modified version of the synthetic-aperture Siral radar designed for Cryosat-2 to study ice thickness in conjunction with measurements made at the same time on the ground.
Siral, built by Alcatel Alenia Space, will be Cryosat-2’s principal observing instrument. But unlike the Cryosat-1 spacecraft, which was lost in an October 2005 failure of the Rockot launch vehicle, Cryosat-2 will have a backup radar payload as well.
The redundancy, which had not been included on Cryosat-1 for financial reasons, is one of several-dozen modifications made by the European Space Agency (ESA) and the Cryosat-2 prime contractor, Astrium Satellites o f Friedrichshafen, Germany.
The Rockot vehicle, a converted Russian SS-19 ballistic missile marketed by the German-Russian Eurockot Launch Services GmbH of Bremen, Germany, has since returned to flight and is scheduled to carry Cryosat-2 into a 720-kilometer, near-polar low Earth orbit in March 2009, from the Plesetsk Cosmodrome in northern Russia.
ESA took less than six months after the loss of Cryosat-1 to decide to build a replacement even though Cryosat-1, like almost all ESA satellites, was not insured.
One reason is the fact that both Cryosat spacecraft borrowed heavily from other missions for their on board equipment.
Richard Francis, Cryosat project manager at ESA, said Cryosat-1 was budgeted at about 145 million euros ($194 million), a figure that includes the development and launch of the satellite, plus operations once in orbit. Cryosat-2 has an almost identical budget — 142 million euros — but only 109 million euros of that is fresh money. The rest is leftover funds for Cryosat-1 commissioning and operations that were not used.
The satellite-construction contract with Astrium, which includes the participation of 25 other companies from ESA member states, is valued at 75 million euros.
Francis said that in addition to a backup radar, the differences between Cryosat 2 and its predecessor include new electronics that were needed because the Cryosat-1 versions are no longer being manufactured.
In addition to the tests of the Siral radar, Cryosat-2 calibrations will be made in part after a four-month Arctic expedition by two Belgian explorers. Their mission, which began in March, will take on-ground measurements of snow depths.
The Siral radar will be able to calculate an iceberg’s height above the sea surface, but will not be able to distinguish how much of the above-surface material is ice, and how much is snow. With a clearer understanding of the depth of the snow, Cryosat-2 science teams will be able to subtract the snow from the observations and then use the normal calculation that seven-eighths of an iceberg is beneath the sea surface.
Laurent Rey, Siral radar program manager at Alcatel Alenia Space, said the 90-kilogram instrument will have three measuring modes to measure the size and shape of maritime and continental ice deposits. With the addition of a backup radar, Cryosat-2 also would perform radar interferometry, offering a more-detailed, stereo view of ice formations, including measurements of the steep walls of ice structures in polar regions.
Adding a second radar on Cryosat 2 has forced other changes to the satellite including the need to provide additional power.