Abstract: The present disclosure provides a system that searches for and finds orbital debris that can be a hazard to satellites and the like, for which the debris is sunlit. The system includes a ground-based telescope pointed at the sky; a detector array that detects images of the sunlit debris crossing the field of the detector; and a processing system that computes tracks from the detector data using a hierarchical algorithm, which builds longer tracks from previously computed shorter tracks, determines whether the computed tracks correspond to valid debris detections, and converts the track computations into debris brightness and debris orbital trajectory.

Abstract: Various disclosed embodiments provide illustrative interferometers, optical phase locked loops, laser systems, interferometry methods, and phase locked loop methods. In illustrative embodiments, light from a laser is split into a first arm and a second arm. Light in an arm chosen from the first arm and the second arm is time delayed. The light in the first arm is split into third, fourth, and fifth arms. The light in the second arm is split into sixth, seventh, and eighth arms. Light in the seventh and eighth arms is phase shifted relative to light in the sixth arm. Light in the third, fourth, and fifth arms is combined with light in the sixth arm and phase shifted light in the seventh and eighth arms, respectively. A frequency correction signal for the laser is generated.