content 24-October-2017 05:57:56

Spacecraft

CHEOPS will be a small spacecraft with a total launch mass of approximately 250 kg. The baseline is to use a standard small satellite platform with some modifications. The spacecraft design was consolidated during the Phase A/B1 study, and Airbus Defence and Space - ECE (CASA) was selected as the platform provider.

CHEOPS has one instrument – a photometer with a single CCD, operating mainly in the visible, that is at the focal plane of an on-axis Ritchey-Chrétien telescope of 32cm diameter (clear aperture diameter of 30cm). All platform requirements are aimed at supporting the functionality of the payload and its ultrahigh photometric precision. The main implications for the platform are related to pointing capabilities and the thermal environment for the payload.

Three views of the CHEOPS spacecraft. Credit: ESA - C. Carreau

The instrument and telescope will be mounted on a stiff optical bench, which defines the interface to the platform, and will be thermally decoupled. A sunshield mounted on the platform will protect the focal plane radiator and detector housing from solar illumination and also carry solar panels for the power subsystem. When stowed for launch, the satellite will measure about 1.5 m × 1.4 m × 1.5 m.
 
The spacecraft will be three-axis stabilised, with a pointing stability of eight arcsec rms over a 48-hour science observation. In a similar manner to the CoRoT mission, the payload will provide centroid data from the target star to the platform's attitude and orbit control system, to enable compensation of low-frequency pointing errors.

During each orbit, the spacecraft will be slowly rotated around the telescope line-of-sight to keep the focal plane radiator oriented towards cold space, enabling passive cooling of the detector.
 


Last Update: 10 July 2014

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