Space Optical Communications Using Laser Beams

This invention provides a new method for optical data transmissions from satellites using laser arrays for laser beam pointing. The system is simple, static, compact, and provides accurate pointing, acquisition, and tracking (PAT). It combines a lens system and a vertical-cavity surface-emitting laser VCSEL)/Photodetector Array, both mature technologies, in a novel way for PAT. It can improve the PAT system's size, weight, and power (SWaP) in comparison to current systems. Preliminary analysis indicates that this system is applicable to transmissions between satellites in low-Earth orbit (LEO) and ground terminals. Computer simulations using this design have been made for the application of this innovation to a CubeSat in LEO. The computer simulations included modeling the laser source and diffraction effects due to wave optics. The pointing used a diffraction limited lens system and a VCSEL array. These capabilities make it possible to model laser beam propagation over long space communication distances. Laser beam pointing is very challenging for LEO, including science missions. Current architectures use dynamical systems, (i.e., moving parts, e.g., fast-steering mirrors (FSM), and/or gimbals) to turn the laser to point to the ground terminal, and some use vibration isolation platforms as well. This static system has the potential to replace the current dynamic systems and vibration isolation platforms, dependent on studies for the particular application. For these electro-optical systems, reaction times to pointing changes and vibrations are on the nanosecond time scale, much faster than those for mechanical systems. For LEO terminals, slew rates are not a concern with this new system.