Design of video processor for multi-head star sensor

Star Sensor, also known as star-tracker, is a high-accuracy 3-axis attitude sensor used onboard spacecrafts. It processes stars from a sky image captured using an area imaging detector (generally 1k × 1k pixels Charge Coupled Device) to generate attitude information. Its accuracy about the boresight is poorer than about the cross-axes. This is improved by using two sensor heads with staggered Fields-Of-View (FOVs) and three to avoid break during occultation of any head. All the sensor heads have identical processing operations. So, the Processing Unit (PU) is made common. This minimizes the system electronics, power consumption and also thermal dissipation on each CH, allowing more efficient cooling of CCD and improving sensor performance. The resulting multiple Camera Heads (CHs) are operated remotely by the common PU. Thus, a programmable Video Processor (VP) is designed for the CH as an efficient data acquisition co-processor to the PU. The VP works in parallel freeing PU for attitude computation from the data acquired from multiple CHs. VP acquires CCD images and pre-processes them to reduce data size, speeding up PU processing. It is programmable for different modes of operation based on full-frame star-search or Region-of-Interest (ROI) readout, thereby providing flexibility, while maintaining rigidity in implementation as required by CCD. Communication of the VP with the PU is configured via low-power high-speed SpaceWire link. The VP is implemented in a low-power FPGA. All instruction and data storage is on-chip.