Weighing some 2.2 metric tons, the satellite will orbit the Earth at an altitude of 700 kilometers starting in 2011. Its orbital path will take it across the poles on each orbit, enabling the radar instrument to scan the Earth in “swaths” as our planet rotates beneath the satellite. Designed as a successor to the present satellites ERS and Envisat to assure continuity in radar-based Earth observation, Sentinel-1 will observe the Earth from orbit for at least seven years. In contrast to its predecessors ERS and Envisat, however, the radar instrument carried by Sentinel-1 will include improvements such as enhanced antenna performance, which in turn will ensure better data quality.
The Astrium-built C-band SAR (Synthetic Aperture Radar) instrument is the core element of the mission. SAR is able to simulate a considerably larger antenna than is, in fact, present, significantly increasing the image resolution. The radar on Sentinel-1 operates in the C band frequency range and has a radar beam with a wavelength of six centimeters, which is able to penetrate forests and scrub to reach the ground. The C band radar registers any movements or changes on the Earth’s surface to within a centimeter.
Sentinel-1 will be equipped with an active antenna made of up 280 individual antennas, including electronic front ends (transmit/receive modules) provided by Thales Alenia Space Italy. The active antenna can be electronically directed towards a new observation terrain without having to be physically moved. Thanks to this technology, several adjacent swaths can be scanned on each overflight and later combined to form a larger overall picture. Astrium has been involved in providing space radars for many years, including the industrial responsibility for Envisat, ERS-1/ERS-2, TerraSAR-X and Tan-DEM-X. EADS Astrium also developed and built the SAR payloads AMI (ERS), ASAR (Envisat), and ASCAT (Metop).
