Development of low-scatter optical edges for starshades

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

doi:10.1117/12.2312694

Cited by 10 publications

(9 citation statements)

References 8 publications

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“…In this study, the nominal radius of the terminal edge is set to 150 nm to approximate the measured terminal radius of the etched coupons. 10 A typical scanning electron microscope image is reproduced here in Fig. 2, revealing a terminal edge with structural variability on a Fig.…”

Section: Introductionmentioning

confidence: 90%

“…7 Past work has studied the use of carbon nanotube-based AR coatings applied to optical edge test coupons. 10,11 While these coatings are extremely dark, with total integrated reflectance of ∼1%, the coatings are typically tens of microns thick. They greatly increase the surface area of the terminal edge, resulting in performance comparable to bare metal.…”

Section: Introductionmentioning

confidence: 99%

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Antireflection coatings on starshade optical edges for solar glint suppression

McKeithen

Shaklan

Sheikh³

et al. 2021

J. Astron. Telesc. Instrum. Syst.

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Starshades are designed to enable the direct observation of an exoplanet by blocking the light of the planet's star from reaching the telescope. As discussed in our companion paper [S. Shaklan et al., "Solar glint from uncoated starshade optical edges," J. Astron. Telesc. Instrum. Syst. 7(2), 021204 (2021)], diffraction and reflection of sunlight incident on the starshade's razor-sharp uncoated edges will appear as glint that may be brighter than the feeble light of the exoplanet. We report on the measurement and modeling of thin, conformal, multilayer antireflection coatings that reduce solar glint by more than an order of magnitude when applied to uncoated edges. We used the Lumerical finite-difference time-domain simulation software suite to determine the performance of coatings designed to work on a flat surface when applied to a sharp, curved edge. Laboratory measurements of coated edges, including a 50-cm long segment, confirm the glint reduction predicted by these models. We consider two coating approaches and compare their performance: a line-of-sight coating and a coating that uniformly covers the entire terminal edge. Starting with a wide range of coating designs emphasizing different angles of incidence and bandpass characteristics, we use Lumerical to account for edge diffraction and reflection, and we optimize the designs for the Starshade Rendezvous Mission and the HabEx mission concept.

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Section: Introductionmentioning

confidence: 90%

Section: Introductionmentioning

confidence: 99%

Antireflection coatings on starshade optical edges for solar glint suppression

McKeithen

Shaklan

Sheikh³

et al. 2021

J. Astron. Telesc. Instrum. Syst.

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“…9 A second mitigating approach is to employ "stealth edges," which is a term we use to describe serrated edges placed where the specular reflection is greatest. 2 The serration removes the specular component for all but the tips and valleys of the serrated portions and has been shown through MAS measurements to reduce scatter by up to an order of magnitude. The ∼1-mm serration period has no effect on the starlight shadow.…”

Section: Mission Performance Assessmentmentioning

confidence: 99%

“…Steeves et al 2 measured the scatter for a variety of edges, including sharp metallic razor-like edges, and sharp edges coated or treated with dark materials, such as Acktar Black, 3 as well as edges machined from pyrolytic graphite, an inherently dark material. They found that the uncoated, sharp metallic edges with a terminal radius of ∼150 nm performed better than the black-coated edges whose radii were ∼10 to 30 μm.…”

Section: Introductionmentioning

confidence: 99%

Solar glint from uncoated starshade optical edges

Shaklan

Hilgemann

McKeithen

et al. 2021

J. Astron. Telesc. Instrum. Syst.

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“…The magnitude of scattered sunlight from various edge geometries has been quantified through stray light models and laboratory experiments. 24,[67][68][69][70][71][72][73][74] In this section, McKeithen et al report on the promising development of AR coatings that are thin and able to reduce the scattering brightness by at least an order of magnitude.…”

Section: Day 2: Starshade Technology and Engineeringmentioning

confidence: 99%

Special Section on Starshades: Overview and a Dialogue

Arenberg

Harness

Jensen-Clem

2021

J. Astron. Telesc. Instrum. Syst.

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This special section is dedicated to starshades: science, engineering, technology, and programmatics. Our reasons for organizing this special section are several fold. First as a new technology and with research accomplished in many institutions, recent results are widely scattered in the literature. As such, we see great value in colocating many of the most recent results. This guest editorial summarizes the 19 contributed papers as the result of a special call for papers. Since this is a rapidly maturing technology, we wanted to colocate a primer with the most current work in the field. It is hoped that this primer will provide a tutorial to the starshade concept and pathway to the literature not in this section. In doing so, we hope to widen the starshade community in terms of engineering and scientific engagements. This tutorial takes the form of a dialogue, where frequently asked questions are answered.

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Development of low-scatter optical edges for starshades

Cited by 10 publications

References 8 publications

Antireflection coatings on starshade optical edges for solar glint suppression

Antireflection coatings on starshade optical edges for solar glint suppression

Solar glint from uncoated starshade optical edges

Special Section on Starshades: Overview and a Dialogue

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