NASA Ames has developed a patent-pending system for optical data transmissions from satellites using laser arrays for laser beam pointing. It is a fine pointing capability for laser beam pointing to augment body pointing by CubeSats in low Earth orbit (LEO). It is simple, static, and compact.
It combines a small lens system and a vertical-cavity surface-emitting laser (VCSEL)/photodetector array in a novel way for laser beam pointing. An incoming laser beam, transmitted from a ground terminal, enters the lens system, which directs it to an element of the pixel array. Each element, or pixel, consists of a VCSEL component/photodetector pair. The photodetector detects the incoming beam and the VCSEL component returns a modulated beam to the lens system, which sends it to the ground terminal. As the incoming beam changes direction, this change is detected by the adjacent photodetector and the laser paired with that photodetector is turned on to keep the outgoing laser beam on target. The laser beams overlap so that the returning beam continues to point at the ground terminal. The VCSEL component may consist of a single VCSEL or a cluster of VCSELs.
The system can very accurately point finely focused diffraction-limited laser beams. Also, simultaneous optical multiple access (OMA) is possible from different transceivers within the area covered by the laser array. For this system, reaction times to pointing changes and vibrations are on the nanosecond time scale — much faster than mechanical fine pointing systems.