Optical Communications Crosslink Payload Prototype Development for the Cubesat Laser Infrared CrosslinK (CLICK) Mission

The Cubesat Laser Infrared CrosslinK (CLICK) mission is a technology demonstration of10 Mbps downlink. On the second flight, with two identical 3U CubeSats, CLICK-B/C, a \u3e20 Mbps crosslink will be demonstrated in addition to downlinks. In this paper representative link budgets for the crosslink are presented, including both communications and beacon lasers. The payload Pointing, Acquisition and Tracking (PAT) system is introduced, and the performance of the second stage closed loop tracking signal processing is assessed. Errors below 1 urad are reported from test and simulation. The communication detector of the payload is a 200 um InGaAs Avalanche PhotoDetector (APD), with a 1 GHz bandwidth and a dynamic range of more than 40 dB provided by programmable gain amplifiers. The APD performance enables a data rate of 17.7 Mbps at a range of 520 km. The timing accuracy of the detector is better than 130 ps