Orbit design of a swarm for ultra-long wavelength radio interferometry with preliminary swarm and thruster sizing

Abstract

Observing the universe in the Ultra-Long Wavelength (ULW) regime has been called the ‘last frontier in astronomy’—real imaging capabilities here are yet to be achieved. Obtaining an image of the sky in this frequency band can be done by employing a swarm of satellites that together act as an interferometer and collect the required imaging information pieces throughout the course of their operational life. Meeting the mission objective is challenging for such a swarm, since this imposes restrictions on the operational environment and the relative position and velocity vectors between the swarm elements. This work proposes an orbit solution in a Heliocentric Earth-Leading Orbit (HELO) for an autonomous CubeSat swarm with chemical thrusters. A distributed formation flying algorithm is used to aid the collection of the required imaging information pieces. Furthermore, the estimated total mission launch mass is reduced by optimising cost functions and finding favourable position and velocity at start of operational life, as well as by finding favourable thrust manoeuvre patterns. The results show that the mission objective—obtaining a 3D map of the Universe in ULW—can be achieved with 68 6U spacecraft (S/C). Moreover, the swarm can remain in a Radio Frequency Interference (RFI) quiet zone of >5 × 10⁶ km, whilst not drifting further than ~ 6.6 × 10⁶ km from Earth for an operational life of one year.