SAR-Lupe was Germany's first reconnaissance satellite system of Bundeswehr used for military purposes. The program started operation in 2008. Continuous operation of the system has ceased at least since 2020; individual SAR-Lupe satellites have been decommissioned or have already burned up in the atmosphere. It is being completely replaced by the SARah system.
The SAR-Lupe program consisted of five identical (770 kg) miniatur-satellites, developed by the German aeronautics company OHB-System, which were controlled by a ground station. A large data archive of images will be kept in a former Cold War bunker belonging to the (Strategic Reconnaissance Command) of the Bundeswehr. The total price of the satellites was over 250 million Euro.
SAR is an abbreviation for synthetic-aperture radar, and "Lupe" is German for magnifying glass.
SAR-Lupe's "high-resolution" images can be acquired day or night through all weather conditions. The satellites are able to provide up-to-date imagery from almost all regions of the world.
The first satellite was launched from Plesetsk in Russia on 19 December 2006, about a year after the intended launch date; four more satellites were launched at roughly six-month intervals, and the entire system achieved full operational readiness on 22 July 2008. The constellation is planned for 10 years of operational life.
The five satellites operate in three 500-kilometre orbits in planes roughly 60ð apart. They use an X-band radar with a 3-metre dish, providing a resolution of about 50 centimetres over a frame size of 5.5 km on a side ("spotlight mode", in which the satellite rotates to keep the dish pointed at a single target) or about 1 metre over a frame size of 8 km à60 km ("stripmap mode", in which the satellite maintains a fixed orientation over the Earth, and the radar image is formed simply by the satellite's motion along its orbit). Response time for imaging of a given area is 10 hours or less. Thales Alenia Space provided the core of the synthetic-aperture radar sensors.
The SAR-Lupe satellites are the first German military satellites.
The testing of SAR-Lupe involved an inverse procedure, in which the satellite, mounted in a radome on Earth, was used to image the International Space Station, whose orbit is reasonably close to the one the satellite will eventually be in. One-metre resolution at the ISS was apparently achieved.
On 30 July 2002 a cooperation treaty between Germany and France was signed, under which the SAR-Lupe satellites and the French Helios optical reconnaissance satellite will operate jointly. Other EU countries have been invited to join as well, and Italy has shown considerable interest.
XSAR of SAR-Lupe is observing in X-band (center frequency of 9.65 GHz corresponding to a wavelength of 3.1 cm).
Prior to an image acquisition, the satellite rolls in an appropriate position and stabilizes its attitude. Then, the SAR image is acquired. After that, the satellite rolls back into its standby attitude and continues to charge its batteries, preparing itself for the next SAR image acquisition.
A replacement of SAR-Lupe, called SARah, entered service starting from 2023. It consists of 3 radar satellites. The SARah satellites are bigger and more capable than those of SAR-Lupe. SARah-1, a phased-array-antenna satellite, launched on Falcon 9 Block 5 on 18 June 2022. SARah-2 and SARah-3, passive-antenna synthetic aperture radar satellites built by OHB SE, were launched on Falcon 9 on 24 December 2023. Both satellites experienced antenna deployment failures after launch, rendering them inoperable. As a result, Bundeswehr officials state that OHB is responsible for building two replacement satellites. After extensive maneuvers the atennas could be deployed and SARah is now fully functional. However the replacement satellites are still being built and will be added additionally.