Image sensor-based pointing, acquisition, and tracking for optical satellite links

Free-Space Optical (FSO) communication is on the verge of becoming an important backbone of the global network infrastructure, and the de facto standard for high-rate data links on satellites, in the near future. In an attempt to overcome link misalignment issues associated with low resolution Four Quadrant Detectors (4QDs) and to widen the scope of feasible optical link scenarios, a detection approach for optical position sensing based on Short-Wave Infrared (SWIR) image sensors is proposed. Thanks to the capability of resolving fine details over a large Field-of-View (FOV), image recognition algorithms can be employed to distinguish different beam objects within the focal plane, making it possible to separate the useful signal from unwanted stray light sources. This classification approach potentially enables Direct-to-Earth (DTE) links during daylight, as these rely on the suppression of the Earth’s albedo superimposing the user signal. Using image acquisition, multivariate tracking algorithms such as Kalman or Particle Filter can be set up to improve the stability of beam tracking needed for more challenging link topologies, such as fast fly-by maneuvers or Intersatellite Links (ISLs) between different orbits. Furthermore, an image-based beam detection system is a useful diagnostic tool for in-orbit calibration or validation of different atmospheric conditions.