Photon-Counting for deep space optical copmmunications

Motivated by the need for higher data volume return from NASA’s future planetary missions, the deep space optical communications (DSOC) technology demonstration (TD) was initiated. The DSOC project integrated a flight laser transceiver to the Psyche Mission spacecraft which launched on Oct. 13, 2023. Ground transmitting and receiving stations implemented by instrumenting existing assets, make more or less weekly optical links with the receding spacecraft. Compared to past and ongoing free-space optical communication (FSOC) TD’s, the key difference for DSOC, is the huge increase in link distance. Photon-counting at both ends of the link were mandated to overcome the link difficulty, defined as data-rate times link-distance squared. In this paper a summary of the photon-counting experience gained so far will be described.