The Berlin’s DLR Institutes of Optical Sensor Systems and Planetary Research developed the Focal Plane Module (FPM, Figure 1) including detector electronics and the sensor control electronics (SEM, Figure 1). This crucial part of the CHEOPS instrument ensures the performance of this high precision photometer.
Figure 2: CCD detector on the Focal Plane Assembly thermally connected to a dedicated radiator
The required photometric precision is achieved using a single, frame-transfer, back-illuminated CCD detector from Teledyne e2v with 1024 × 1024 pixels and a pixel pitch of 13 µm (Figure 2). The CCD is mounted in the focal plane module of a 32 cm diameter, f/8, on-axis Ritchey-Chrétien telescope, and will be passively cooled down to -40°C. Since the depth of Planet transits is 100 parts-per-million (ppm), this requires a photometric precision of 20 ppm (goal: 10 ppm) in 6 hours of integration time, equivalent to the transit duration of a planet with a revolution period of 50 days. Therefore both, the CCD detector and the low noise sensor electronics are thermally stabilized with better than 10 mK.
Figure 3: Focal Plane Module mounted on the Optical Telescope Assembly at University in Bern
