Design and Characterization of the sCMOS Detector for the Comet Interceptor Camera

Kurzfassung

Comet Interceptor will travel to an as-yet undiscovered comet, making a flyby of the chosen target when it is on the approach to Earth's orbit. The paper presents the architecture and performance of the backside illuminated sCMOS detector architecture and the corresponding detector control and front-end electronics as part of the CoCa camera. The paper presents details of the selected back-illuminated low readout noise CIS115 detector from e2v/Teledyne, the design, implementation and test of the space qualified radiation tolerant readout electronics. The radiation tolerant detector in combination with the space qualified front end electronics resulted in an excellent readout noise performance of less than 3e-. The paper presents electro-optical tests based on EMVA standard. Radiation test results done by our colleagues at the Open University provide minor performance degradation of the detector at the predicted mission radiation environment. A novel readout scheme provides in rolling shutter operation exposure times less than the frame time. Electro-optical test results over the operation temperature range are part of the presentation. The paper discusses also interesting effects which were observed during detector characterization. An extensive investigation of the performance and redesign of the detector control (clocking and biasing) did provide major improvements. A new setup for detector characterization consisting of a cryostat, tunable collimated light source, and versatile data acquisition system is currently being commissioned. The setup enables testing optical and infrared sensors in the 400 to 14000 nm wavelength range and the devices under test can be cooled to cryogenic temperatures of down to 50 K under vacuum condition. 32 spectral band passes with bandwidths of λ/Δλ ≥50 are available for spectral characterization, covering the full range of 400 to 14000 nm. The setup can be used to characterize responsivity, detectivity, noise equivalent temperature difference, dark current, linearity, dynamic range, well depth, and pixel response non-uniformity. We will report on first results for the characterization of imaging sensors proposed to be used on upcoming solar system exploration missions.