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Astrium has completed the radar instrument for the Sentinel-1A environmental satellite and will deliver it to Thales Alenia Space (TAS) in Rome for installation on the satellite. The heart of the mission is the C-band Synthetic Aperture Radar (SAR) instrument built by Astrium whose basic technologies, like the T/R modules and the Front End Electronics for the antenna as well as the advanced data management and transmission subsystems has been built by Thales Alenia Space.
Its most noticeable characteristic is its active electronic antenna measuring 12.30 m by 0.90 m. In SAR, the flight movement of the satellite simulates a virtual antenna much larger than the physical one on board the satellite. This considerably improves the resolution of the resulting images. The C-band radar beam, which has a wavelength of 6 cm, penetrates crops to reach the surface, and can determine changes in the Earth’s surface to millimetres.
The Sentinel-1 SAR instrument, which was built by Astrium in Friedrichshafen, Germany, is equipped with a waveguide antenna, which consists of 560 individual antennas coupled to each other. The connected SAR electronics were supplied by Astrium in Portsmouth, UK. The active antenna can be aimed electronically at an area to be scanned without having to be moved. With the help of this technology several neighbouring strips can be scanned at once, and subsequently combined to provide an overview.
“We want the instruments for the Sentinel-1 satellites to be another chapter in our space radar success story,” said Eckard Settelmeyer, Director in Germany of Earth Observation, Navigation and Science at Astrium. “As well as bearing overall industrial responsibility for the European ERS-1/ERS-2 and Envisat satellites, Astrium has also developed and built the AMI (ERS), ASAR (Envisat) and ASCAT (MetOp) radar payloads. On top of this, Astrium has overall responsibility for the German TerraSAR-X and TanDEM-X radar satellite projects, as well as the planned phased array satellites of the SARah program – all in all, a long and successful line of technologies and products.”
Sentinel-1A, led by TAS as prime contractor, is the first in a series of sentinel satellites for the European Copernicus programme, a joint venture of the European Commission, the European Space Agency (ESA) and the European Environmental Agency (EEA). Copernicus will create a sustainable European satellite network to collect and evaluate environmental data and for civil safety and humanitarian needs.
From 2014 onwards, the satellite – which weighs about 2.3 tonnes – will orbit the Earth at an altitude of about 700 km. On each orbit it will fly over the North and South Poles, scanning ‘strips’ of the Earth with the radar instrument as the Earth revolves beneath it. One new development is that the Astrium radar will make it possible to record data continuously (around the clock). Sentinel-1A, which will be launched on a Soyuz rocket from the European spaceport in Kourou, French Guiana, is set to observe the Earth from its orbit for at least seven years.
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