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25th Anniversary of the Space Shuttle Missions SIR-C/X-SAR
07 October 2019
Earth observers like to 'look' at the Earth with radar sensor systems. They allow high-precision images of the surface and have a great advantage over optical cameras: images can be taken not only in excellent visibility, but also in cloudy conditions, rain or at night. Research into space-based radar technologies has a long history. A milestone was the multi-frequency radar system SIR-C/X-SAR. 25 years ago, the Space Shuttle Endeavour flew around the world twice, in April and October 1994. It was the most advanced civil radar in Earth orbit at that time – and for Earth observation it was as big a step as the transition from black-and-white to colour film in photography.
The mission, with the rather unwieldy name SIR-C/X-SAR, was a joint venture between the German Space Agency (Deutsche Agentur für Raumfahrtangelegenheiten; DARA) – today's DLR Space Administration – the US National Aeronautics and Space Administration (NASA) and the Italian space agency (Agenzia Spaziale Italiana; ASI). In addition to the C- and X-band radars, an L-band radar was operated in parallel. This 'multi-frequency' Synthetic Aperture Radar (SAR) proved its performance during two 10-day spaceflights. The radar data acquired during these missions became the basis for more than 5000 scientific publications in the years that followed.
Image credit: NASA - Artist's impression from 1994 of the SIR-C/X-SAR antennas in the payload bay of Space Shuttle Endeavour