Impact of pointing performance on the optical downlink for the Optical PAyload for Lasercomm Science (OPALS) system Results from pre-flight laboratory testing

The Optical PAyload for Lasercomm Science (OPALS), developed at JPL, is a technology demonstration project which is set to begin operations from the International Space Station in early 2014. Its goal is to demonstrate the feasibility of an optical communication link from low-Earth orbit (LEO), i.e. the ISS, to a ground terminal located at JPL’s Optical Communications Telescope Laboratory (OCTL). Pointing performance is a key consideration, and often a driver, in the design of space-to-ground optical communications links, as was the case for our project. In this paper we discuss how the allocations for the pointing system were derived and the impact of the pointing performance on the optical downlink. We address the contributions from static and quasi-static pointing offsets (bias) as well as those from the fast-dynamic disturbances produced by the two-axis gimbal and control loop (jitter). Results from laboratory testing are presented and compared to the