Precise Formation-Flying Telescope in Target-Centric Orbit: the Solar Case
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Precise Formation-Flying Telescope in Target-Centric Orbit: the Solar Case Pascal Saint-Hilaire1
· Jeffrey E. Marchese1
© The Author(s) 2020
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 ∼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. Keywords Formation flying · Precise Formation Flying · Heliocentric · Telescope
Introduction 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). The European Space Agency’s Proba3 [1, 2], currently scheduled to be launched in 2022, attempts such a feat, with a coronograph spacecraft separated from a telescope spacecraft by a distance of ≈150 m in high Earth orbit. The Sun-coronograph-telescope alignment is planned to last about six hours during each ∼day-long length of the highly eccentric orbit. Besides Pascal Saint-Hilaire
[email protected] 1
Space Sciences Laboratory, University of California, Berkeley, 7, Gauss Way, Berkeley, 94720, CA, USA
The Journal of the Astronautical Sciences
an occulter-telescope pair, there are several other possible applications for such a concept. For example in the X-ray regime, the optics can be a Fresnel Zone Plate [3], a focusing optics mirror (the longer focal length enables shallower incidence angle on the mirrors, allowing higher energies to be reached), or a coded-mask or (rotating) grid allowing e.g. higher angular resolutions. We are interested in the case of the Sun as a target, with the Optics spacecraft and Detector spacecraft in a “scopocentric” orbit around it (Fig.1), and we will use the term “Precise Formation Flying,” or PFF, to refer to the combination of TargetOptics-Detector alignment maintenance and Optics-Detector distance maintenance. This paper strives to make the case for scientists requiring large optics-to-detectors distances for the next generation of space instrumention that the time is nigh, and that a solar application is probably an easy first step. Section “Differential Accelerations” details
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