The Photon Counting Camera (PCC) is a single-photon sensitive laser communication camera that will launch on board the NASA PSYCHE spacecraft, part of the Deep-Space Optical Communication (DSOC) technology demonstration mission. The PCC comprises a single-photon sensitive Geiger-mode Avalanche Photo Diode (GmAPD) array connected to an electronics board designed to power, configure, and read out the array. The logic on the electronics board prevents accidental damage to the array, provides health and status information about the array and provides a simple interface to the downstream data processing modules. The array and electronics board are mounted into the chassis, which provides precise alignment between the optics bench and the detector as well as a path to radiate waste heat. We discuss the current design of the camera, including the electronic, thermal, and structural design. We also discuss some of the design challenges and our roadmap to building the flight unit.
Delivery of large volumes of data from low-Earth orbit to ground is challenging due to the short link durations associated with direct-to-Earth links. The short ranges that are typical for such links enable high data rates with small terminals. While the data rate for radio-frequency links is typically limited by available spectrum, optical links do not have such limitations. However, to date, demonstrations of optical links from low-Earth orbit to ground have been limited to ~10 to ~1000 Mbps. We describe plans for NASA’s TeraByte InfraRed Delivery (TBIRD) system, which will demonstrate a direct-to-Earth optical communication link from a CubeSat in low-Earth orbit at burst rates up to 200 Gbps. Such a link is capable of delivering >50 Terabytes per day from a small spacecraft to a single small ground terminal.