Precise Formation-Flying Telescope in Target-Centric Orbit: the Solar Case

Pascal Saint-Hilaire,Jeffrey E Marchese

doi:10.1007/s40295-020-00231-2

Pascal Saint-Hilaire, Jeffrey E Marchese

Open Access

https://doi.org/10.1007/s40295-020-00231-2

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Abstract

We present the general concept of a telescope with optics and detectors mounted on two separate spacecrafts, in orbit around the telescope’s target (scopocentric or target-centric orbit), and using propulsion to maintain the Target-Optics-Detector alignment and Optics-Detector distance. Specifically, we study the case of such a telescope with the Sun as the target, orbiting at sim 1 AU. We present a simple differential acceleration budget for maintaining Target-Optics-Detector alignment and Optics-Detector distance, backed by simulations of the orbital dynamics, including solar radiation pressure and influence of the planets. Of prime interest are heliocentric orbits (such as Earth-trailing/leading orbits or Distant Retrograde Orbits), where thrust requirement to maintain formation is primarily in a single direction (either sunward or anti-sunward), can be quite minuscule (a few m/s/year), and preferably met by constant-thrust engines such as solar electric propulsion or even by solar sailing via simple extendable and/or orientable flaps or rudders.

Highlights

To date, spaceborne telescope boom lengths have rarely exceeded 15 m, and achieving much greater separation distances in space between optics and detectors will likely require precise formation flying (PFF)
We present the general concept of a telescope with optics and detectors mounted on two separate spacecrafts, in orbit around the telescope’s target, and using propulsion to maintain the Target-Optics-Detector alignment and Optics-Detector distance
Currently or in coming years, CubeSats and SmallSats can be expected to be given regular rideshares to orbits more propitious to PFF telescopes, or to regions from which it is easier to get to such orbits: GTO, GEO, Mars Transfer Orbits, Earth-Sun L1/L2, and heliocentric

Summary

Introduction

Spaceborne telescope boom lengths have rarely exceeded 15 m, and achieving much greater separation distances in space between optics and detectors will likely require precise formation flying (PFF). Section “Thrust the Detector Spacecraft must Exert to Sustain its non-Keplerian (“NK”) Orbit” deals with compensating for the non-keplerian orbit of the Detector spacecraft, Section “Differential Acceleration due to Tidal Effects from Other Celestial Bodies” deals with compensating for the disruptive effects from other bodies than the one being orbited, and Section “Differential Acceleration due to Solar Radiation Pressure” deals with the effects of radiation pressure (which dominate when the formation-flying telescope is sufficiently far away from all celestial bodies). Note that the tidal disruptive effects due to the orbited target are already included in the results δaDNK of “Thrust the Detector Spacecraft must Exert to Sustain its non-Keplerian (“NK”) Orbit”. If the target is the Sun, the difference in solar pressure between distances rO and rD is compensated by: δaDRP,r

AU 2 rO

Discussion

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Conclusions