The approximately 1.3-ton TerraSAR-X spacecraft is based on the EADS Astrium Flexbus-concept and has an extensive heritage from the successful CHAMP and GRACE missions. The 5 metre long and 2.4 metre wide satellite bus features a structure with a hexagonal cross-section. One of the six sides carries the 5-metre-long and 80-centimetre-wide radar antenna. The electronics boxes of the SAR instrument and the satellite bus are also fitted on the side faces of the structure, as is the satellite’s solar generator, 5.25 square metres in area, which supplies energy using gallium arsenide solar cells.
System components of the TerraSAR-X satellite
The data recorded by the SAR instrument are transferred via a downlink antenna to the ground receiving station. The downlink antenna is attached to a 3.3-metre mast, to avoid interference from the radar antenna. The mast was folded up during the launch and extended after the satellite reached orbit. This arrangement allows simultaneous acquisition of new data by the radar and transmission of previously stored data to the ground.
The high-accuracy pointing of the satellite is implemented by means of star sensors that are installed near the radar antenna, so that the required accuracy of antenna alignment (65 arcseconds) can be achieved. A GPS receiver located on board enables precise determination of the orbit.
Alongside the SAR instrument, two secondary payloads are being flown on TerraSAR-X:
- The Laser Communication Terminal (LCT)
The LCT is a technology demonstrator that is used for in-orbit verification of rapid optical data transfer in space. Using the instrument, financed by DLR and built by Tesat, a link can be established between TerraSAR-X and a ground station.
- The Tracking, Occultation and Ranging Experiment (TOR)
The TOR experiment was prepared by the German Research Centre for Geosciences (GeoForschungsZentrum; GFZ) in Potsdam, in collaboration with the Center for Space Research of the University of Texas (UT-CSR) for a flight on TerraSAR-X. It consists of the IGOR dual frequency GPS receiver together with a laser reflector unit. IGOR allows determination of the satellite’s orbit with an accuracy of down to 10 centimetres.
|TerraSAR-X at a glance:|
|Launch date:||15 June 2007|
|Launch site:||Baikonur, Kazakhstan|
|Orbit altitude:||514 kilometres|
|Satellite mass:||about 1230 kilograms|
|Satellite size:||5 metre height x 2,4 metre diameter|
|Radar frequency:||9.65 GHz|
|Power consumption:||800 Watt (mean)|
|Data reception, Mission operation:||DLR, Neustrelitz, Oberpfaffenhofen, Weilheim|
|Lifetime:||at least 5 years|