Echoes from the past: the communication layer of a nanosatellite swarm

The Orbiting Low Frequency Antennas for Radio Astronomy (OLFAR) project is aimed at developing a low-frequency radio telescope to observe the cosmic radiation in the 0.3–30-MHz domain. This frequency band is one of the last unexplored regions of radio astronomy, and studying it will reveal details about the so-called Dark Ages of the Universe, exoplanets, and other celestial bodies and phenomena. Building a telescope to capture these ultra-long electromagnetic (EM) waves requires overcoming a few obstacles such as the high level of terrestrial radio-frequency interference (RFI) or size of the required aperture (10–1,000 m). OLFAR will consist of a swarm of 50 or more nanosatellites that will sense the EM waves of interest, distribute the data within the swarm, process it, and send the end results to a base station (BS) on Earth. The scientific goal of the mission as well as the implementation details (the lunar orbit, the large number of spacecraft, the distributed processing, and the cubesat platform) will impose stringent restrictions on the communication layer of the OLFAR swarm. Both inter-satellite as well as swarm-to-Earth communication will have to deal with high data rates (in the order of Mbps), and will have to cover large distances (100 km and 400,000 km, respectively). The objective of this research is to determine whether a swarm of nanosatellites can meet the data flow requirements of a high-resolution imaging instrument for low-frequency radio astronomy. This thesis proposes solutions for the data distribution problems within the OLFAR swarm and from the OLFAR swarm to Earth. The solutions include a data distribution topology and an ISL design for in-swarm communications, as well as a cooperative downlink strategy and an antenna system for the swarm-to-Earth communication.