Development of low-scatter optical edges for starshades

John Steeves; Hyeong Jae Lee; Evan Hilgemann; Dylan McKeithen; Christine Bradley; David Webb; Stuart Shaklan; Stefan Martin; Douglas Lisman

doi:10.1117/12.2312694

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10 July 2018 Development of low-scatter optical edges for starshades

John Steeves, Hyeong Jae Lee, Evan Hilgemann, Dylan McKeithen, Christine Bradley, David Webb, Stuart Shaklan, Stefan Martin, Douglas Lisman

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Proceedings Volume 10706, Advances in Optical and Mechanical Technologies for Telescopes and Instrumentation III; 107065K (2018) https://doi.org/10.1117/12.2312694
Event: SPIE Astronomical Telescopes + Instrumentation, 2018, Austin, Texas, United States

Abstract

Starshades, combined with future space telescopes, provide the ability to detect Earth-like exoplanets in the habitable zone by producing high contrast ratios at small inner working angles. The primary function of a starshade is to suppress light from a target star such that its orbiting planets are revealed. In order to do so, the optical edges of the starshade must maintain their precise in-plane profile to produce the necessary apodization function. However, an equally important consideration is the interaction of these edges with light emanating from our own Sun as scattered and/or diffracted sunlight can significantly degrade the achievable contrast. This paper describes the technical efforts performed to obtain precision, low-scatter optical edges for future starshades. Trades between edge radius (i.e. sharpness) and surface reflectivity have been made and small-scale coupons have been produced using scalable manufacturing processes. A custom scattered light testbed has been developed to quantify the magnitude of scattered light over all sun angles. Models have also been developed to make predictions on the level of reflected and/or diffracted light for various edge architectures. The results of these studies have established a current baseline approach which implements photochemical etching techniques on thin metal foils.

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John Steeves, Hyeong Jae Lee, Evan Hilgemann, Dylan McKeithen, Christine Bradley, David Webb, Stuart Shaklan, Stefan Martin, and Douglas Lisman "Development of low-scatter optical edges for starshades", Proc. SPIE 10706, Advances in Optical and Mechanical Technologies for Telescopes and Instrumentation III, 107065K (10 July 2018); https://doi.org/10.1117/12.2312694

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