Comparing Adaptive Optics Approaches for Nasa Lcrd Ground Station #2

NASA's Laser Communication Relay Demonstration (LCRD) aims to demonstrate a geosynchronous satellite laser communications (lasercom) relay between two independent ground terminals. We report on the design of two adaptive optics (AO) techniques for LCRD Ground Station #2 (GS-2). GS-2 leverages the ground terminal developed for NASA's Lunar Laser Communications Demonstration (LLCD). Equipping GS-2's 40cm diameter receive telescope with AO to mitigate atmospheric turbulence effects will enable the use of single mode, optically preamplified receivers for high data-rate near-Earth relay applications. In this work a direct wavefront sensing AO approach using a Shack-Hartmann sensor and a continuous facesheet micro-electro-mechanical system (MEMS) deformable mirror (DM) was compared with an indirect sensing, hill-climbing or multidither approach using a segmented MEMS DM. Design concepts and recent experimental progress for the two approaches are presented.