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

Alisa S Nevinskaia,Mark J Bentum,Steven Engelen,Bert Monna,Marc C Naeije

doi:10.1016/j.actaastro.2021.07.035

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.

Highlights

The idea of space-based radio astronomy, to overcome ionospheric effects, dates back to when space exploration was still in its infancy [17,18,19,28], real imaging capabilities in the Ultra-Long Wavelength (ULW) regime (0.1–30 MHz) are—in contrast to all other major wave bands—currently yet to be achieved
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)
Since Earth is a major source of Radio Frequency Interference (RFI), Earth orbits are not suitable and an oper ational location in deep space must be selected—either at the far side of the Moon (as has previously been shown by the Radio Astronomy Ex plorer 2 (RAE-2) mission, see Ref. [1]) or ~ 5 × 106 km from Earth [5, 33] (Bentum and Boonstra [5] conclude this based on extrapolations of RFI measurements from a number of previous missions)

Summary

Introduction

The idea of space-based radio astronomy, to overcome ionospheric effects, dates back to when space exploration was still in its infancy [17,18,19,28], real imaging capabilities in the ULW regime (0.1–30 MHz) are—in contrast to all other major wave bands—currently yet to be achieved. Imaging in this virtually unexplored region is driven by a multitude of science cases (e.g. seeking the Dark Ages signal—an echo of the era from before the first stars were born) and could impact our knowledge of the Universe in an unprecedented way [7,13,23,33, 46]. Angular resolution l is the ratio between the αwm≈aavxλeim/leDun≈mgthλ/⃦⃦λbsaiaj‖snemdlaixnte[h3e3]al;penneorgtttuehrheerD⃦⃦esitojh‖fmaataxamn oionnftoelritfhearincomteeiltneestreciorsfpeaerodomirsetrttiehbre: uted telescope that comprises multiple smaller antennas; an (http://creativecommons.org/licenses/by/4.0/)

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Discussion

Conclusion