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Thermal control

Thermal control of the spacecraft, its subsystems and of most of the experiments is achieved by passive means in conjunction with a commandable internal/external power dump and heater system. This involves an optimised layout of subsystems which avoids hot spots on the spacecraft platform, an efficient thermal-blanket design in order to minimise the solar input, the compensation, by the power dump system, of heat fluxes which are caused by the varying solar input and a heater system for individual critical units.

The most stringent requirements on the thermal subsystem are to guarantee a temperature above +2 °C at all times for the hydrazine of the Attitude and Orbit Control Subsystem (AOCS) and a temperature below +35 °C for all experiment solid-state detectors. All spacecraft walls are covered with thermal multilayer blankets, which are closely fitted around the experiment-sensor apertures. The blankets consist typically of 20 layers of aluminized mylar. The outermost layer is kapton, coated with a transparent conductive coating (indium tin oxide) to provide an electrically conductive outer spacecraft surface. Heat rejection is performed by a thermal radiator, located on the rear of the spacecraft and covered by a 2 mm kapton foil. All units external to the spacecraft (for example, several experiments) are thermally decoupled from the interior.

Last Update: 30 November 2006

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