Vision-based navigation for rendezvous, docking and proximity operations

A novel approach for vision sensing and vision-based proximity navigation of spacecraft is presented. We have recently invented a new sensor which utilizes area Position Sensing Diode (PSD) photodetectors in the focal plane of an omni-directional camera. These analog detectors inherently centroid incident light, from which a line of sight vector can be determined. PSDs are relatively fast compared to even high speed cameras, having rise times of about five microseconds. This permits light sources to be structured in the frequency domain and utilization of radar-like signal processing methods to discriminate target energy in the presence of even highly cluttered am bient optical scenes. We have developed the basic concepts, designed first generation vision sensors based on this approach and carried out proof-of-concept experimental studies. Our results show that a beacon's line of sight vector can be determined with an accuracy of one part in 5,000 (of the sensor field of view angle) and at a distance of 30m with an update rate of 50Hz. In practice, measured directions toward four or more beacons would typically be used. We have also developed an associated six degree of freedom navigation algorithm that is readily applicable to rendezvous, docking, and proximity operations; we have verified that this algorithm is robust and compatible with real-time, on-board computational constraints. This paper summarizes analytical, computational, and laboratory experimental results supporting the efficiacy and practicality of this approach.