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CryoSat structual view
CryoSat structural view

1 Radiator: a heat-radiating panel at the top of the nose structure which houses the SIRAL electronics under the solar array.

2 Star tracker: three mounted directly on the antenna bench.

3 Antenna bench: stable and rigid support structure isostatically mounted to the satellite nose.

4 SIRAL antennae: rigid mounted to the antenna bench immediately beneath the SIRAL electronics.

5 Laser retroreflector: reflects incoming laser tracking pulses directly back to the ground-based laser station.

6 DORIS antenna: receives signals from a global network of radio beacons for orbit determination.

7 X-band antenna: transmits the huge volume of SIRAL measurement data to the ground when the satellite is above the horizon at Kiruna, Sweden.

8 S-band helix antenna: receives telecommands from the ground and transmits status and monitoring information.

CryoSat is a satellite with a single mission objective – therefore, the selection of its orbit and basic characteristics has been entirely driven by the scientific requirements.

Unlike most remote sensing satellites, CryoSat's orbit is not to be Sun-synchronous, but will go through frequent eclipse phases. This has presented some challenges in the satellite design; all parts will at some time be exposed to the full heating power of the Sun, while at other times parts of the satellite will be in permanent shadow for weeks on end.

CryoSat does not have any deployable solar panels; in fact the satellite has no moving parts at all, except for some valves in the propulsion system. This has enabled a very significant cost saving, but does pose some problems for the provision of adequate solar power in CryoSat's unusual orbit. The solar panels are fixed to the satellite body, forming a 'roof' at a carefully optimized angle, which provides adequate power under all orbital conditions and still fits within the launch vehicle.

The other area that receives particular attention has been the mounting of the two SIRAL antennas. The baseline on which the SIRAL antennas were mounted has to be completely stable and has to ensure minimal thermal expansion. Any distortion will lead to errors in the assumed location of the echo and hence the elevation of the surface of the ice. The challenge has been met by designing the structure to be intrinsically stable and providing auxiliary attitude measurement sensors, in the form of star trackers, mounted directly onto the antenna bench structure.