A flexible cost-effective detector controller for space

Ground-based infrared observations are often limited by atmospheric absorption and emission. Space-based instruments avoid this, but introduce unique technical challenges. We present the design of a flexible, compact, and cost-effective detector controller for space, based on commercial off-the-shelf components. Its architecture provides up to 50 configurable clock sequences and 16 biases, 32 16-bit video channels and several general-purpose ports. This allows for full control of CMOS detectors including Leonardo 'SAPHIRA' avalanche photodiode arrays (APD) which represent current state of the art in low-noise infrared imaging. The controller's core logic is implemented on a Xilinx Kintex Ultrascale field programmable gate array (FPGA). The architecture includes a user-command set to load configuration registers and clocking sequences into RAM. A sequencer state machine controls sequential memory readout to generate the custom clock signals on the relevant outputs. DC biases are set using configurable digital-to-analog converter (DAC) control outputs. Analog-to-digital converters (ADCs) interface the pixel voltages to the controller's video inputs, where the frame data is reformatted, buffered and eventually streamed off-chip over a high-speed interface such as CameraLink. A combination of triple modular redundancy, scrubbing and error correction techniques are used to mitigate on-chip radiation-induced upsets. A fault-injection scheme will be used to test the error-recovery performance of the controller in a simulated low-Earth orbit radiation environment. An early prototype system (see Figure 1) has been constructed as proof-of-concept for operation of a 320 * 256 SAPHIRA APD. A Xilinx Kintex-7 FPGA evaluation board acts as the primary controller, while in-house designed boards perform bias voltage regulation and sequencing, video signal conversion and cryogenic pre-amplification. A Python-based command line interface enables user control over USB3.0, providing up to 2Gbps data transfer.