Siral, a New-Gen Radar Altimeter-Interferometer for the CryoSat Satellite

• Built by Thales Alenia Space, the SIRAL instrument is designed to monitor polar ice

(Cannes, April 1, 2010) -- Scientists worldwide are impatiently awaiting critical data to be supplied by the Thales Alenia Space-designed SIRAL interferometric radar altimeter, which will help them assess the size and thickness of polar ice and how it changes over time. By more precisely measuring its surface and changes in elevation, scientists will be able to better understand the ice cycle and our changing climate.

Slated for launch on April 8th from the space centre in Baikonur, Kazakhstan, the CryoSat - ESA's Ice mission is part of the ESA's Living Planet programme. The satellite was built by EADS Astrium as prime contractor, and features the SIRAL (SAR Interferometric Radar Altimeter) instrument, designed to study polar terrain elevations to provide a highly accurate topography of this shifting environment. The satellite will be placed in polar orbit at an inclination of 92o. It will fly over the poles at an altitude of 720 km, and will circle the Earth once every 100 minutes.

According to Laurent Rey, SIRAL project manager at Thales Alenia Space: "Thanks to SIRAL, scientists will be able to combine data on the size of polar ice sheets with elevation measurements. This will enable them to study not only the current state of this natural environment, but also how fast it is changing globally. The data gathered will give us additional information to help us better understand the Earth's climate."

SIRAL is an interferometric radar altimeter derived from the Poseidon altimeter on the Jason satellite. An innovative instrument in a compact package weighing just 90 kg, SIRAL combines three measurement modes:

-- Low-resolution, used for conventional altimetric measurements of the relatively stable continental ice sheets in the Antarctic.
-- Synthetic Aperture Radar (SAR) mode, used for high-resolution measurement of floating sea ice, enabling the indirect measurement of the thickness of ice floes.
-- Interferometric radar mode, to study more contrasted elevations, like the very active areas located at the junction between the ice floes and Antarctica, and Greenland.

SIRAL features very high resolution; using its two antennas, it can scan the ground in 250-meter swaths, enabling it to more precisely determine the transitions between sea and ice. The CryoSat satellite is fitted with a redundant SIRAL instrument, used as a backup if necessary to ensure the long-term success of this critical scientific mission.

"Our challenge was to develop and produce two high-precision SIRAL instruments for this CryoSat mission," adds Laurent Rey. "This type of instrument demands an extensive effort to deliver the required performance. The adjustments needed are extremely delicate, and doing this successfully depends on real technological prowess."

A 6-month in-orbit validation phase is scheduled to check all instrument configurations, and to analyse its in-orbit performance in relation to the highly variable terrain that it has to measure.

Source : Thales Group (Paris: HO.PA)