Lunar Inter-Spacecraft Optical Communicator

The inter-spacecraft omnidirectional optical communicator (ISOC) is currently being developed by Chascii to provide fast connectivity and navigation information to small spacecraft forming a swarm or a constellation in lunar space. The lunar ISOC operates at 1550 nm and employs a dodecahedron body holding 6 optical telescopes and 20 external arrays of detectors for angle-of-arrival determination. In addition, the ISOC includes 6 fast avalanche photodetectors (each furnished with external gain optics) for high data rate connectivity. The ISOC should be suitable for distances ranging from a few kilometers to a few thousand kilometers. It will provide full sky (<tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$4\pi$</tex> steradian) coverage and gigabit connectivity among smallsats forming a constellation around the moon. It will also provide continuous positional information among these spacecraft including bearing, elevation, and range. We also expect the ISOC to provide fast low-latency connectivity to assets on the surface of the moon such as landers, rovers, instruments, and astronauts. Chascii is building a lunar ISOC including all its transceivers, optics, and processing units. We are developing the ISOC as a key candidate to enable LunaNet. In this paper, we will present the development status of the ISOC's transceivers as well as link budget calculations for operations around the moon using pulse-position modulation. We will also discuss the use of Delay-Tolerant Networking in the ISOC processor to achieve secure and encrypted connectivity around the moon. We believe the ISOC, once fully developed, will provide commercial, high-data rate connectivity to future scientific, military, and commercial missions around lunar space and beyond.