Design of Laser Communications Module for Small Satellites

Laser communications (lasercom) has the potential to transform scientific, defense, and commercial satellite communications platforms. Lasercom has been successfully demonstrated on several space platforms ranging from low Earth orbit to lunar orbit, and multiple ongoing efforts have focused on bringing lasercom to nanosatellites which have significant size, weight, and power constraints. Lasercom has become a possibility on nanosatellites due to recent advances in nanosatellite attitude determination and control, but precision pointing is still a major challenge for this class of satellite. This work focuses on achieving precise pointing with a two-stage architecture on resource-constrained nanosatellites to enable high bandwidth lasercom. CubeSat body pointing is augmented with a fast-steering mirror (FSM) that steers the lasercom downlink. Simulation and hardware-in-the-loop testing resulted in pointing accuracy on the order of arcseconds while slewing to track a ground station from low-earth orbit. In addition to the nanosatellite terminal, development of a versatile, low-cost ground station is needed to enable widespread use of lasercom on small platforms. Current ground station technology resembles astronomical observatories in terms of infrastructure and cost. This research examines the use of an amateur telescope as an optical ground station, reducing the cost from millions of dollars to tens of thousands of dollars. Given the availability of radio ground receivers, an equally versatile optical receiver makes lasercom much more attractive. A low-cost, rapidly-deployable optical ground station is developed with demonstrated satellite tracking performance better than 5 arcseconds root-mean-square (RMS).