Solar glint from uncoated starshade optical edges

Shaklan, Stuart; Hilgemann, Evan; McKeithen, Dylan; Martin, Stefan; Steeves, John; Webb, David R.; Lisman, Douglas

doi:10.1117/1.jatis.7.2.021204

Cited by 7 publications

(10 citation statements)

References 13 publications

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“…Table 6 reproduces the 95% confidence level magnitude of the azimuthally averaged brightness of solar glint lobe within a diffraction-limited photometric aperture at the inner working angle (IWA) for uncoated AM edges published in Ref. 9. We show the improvement ratio for the expected as-manufactured performance (column 6 of Table 5) and equivalent ΔMag evaluated at several Sun angles.…”

Section: Magnitude Of Solar Glint Lobesmentioning

confidence: 71%

“…Preliminary scatter data were gathered experimentally using the single-angle scatterometer (SAS) at JPL. Details of the design and calibration of the SAS are given in Shaklan et al, 9 with a brief description given here. Figure 6 shows the setup of the instrument.…”

Section: Comparison With Experimental Datamentioning

confidence: 99%

“…To determine the absolute level of scatter, the data are compared with a reference coupon with an absolute scatter ratio that was measured with another instrument, the MAS. 9 The SAS then moves along the length of the test coupon to the next point and repeats the alignment and measurement process, eventually measuring the scatter performance of the test coupon along its entire length. Figure 7 shows the results for four manufactured coatings, each applied to three coupons at different coating angles, as well as a representative uncoated coupon, labeled B27 for its manufacturing lot and sequence.…”

Section: Comparison With Experimental Datamentioning

confidence: 99%

“…The uncoated edges scatter light at close to this value, while the coated edges scatter much less light. The measurement errors in Table 4 include the quadrature addition of a 1σ value of AE16% determined from instrument calibration and coupon statistics reported in our previous work 9 and a AE30% estimate of the standard error of the median. The standard error of the median was determined by measuring a 500-mm long -coated edge (Fig.…”

Section: Comparison With Experimental Datamentioning

confidence: 99%

“…It has been shown that an amorphous metal (AM) iron-nickel alloy foil with a sharp, etched edge (radius ∼150 nm) has the ability to control the glint to a visual magnitude of V ∼ 25 for the SRM and V ∼ 27 for the HabEx mission concept. 9 The application of an antireflective (AR) coating to the optical edge can reduce the scatter by minimizing the reflection component and destructively interfering or apodizing the diffraction component. The design is challenging, however, because both geometrical reflection at highly curved surfaces and diffraction from subwavelength diameter structures are in play.…”

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: Magnitude Of Solar Glint Lobesmentioning

confidence: 71%

Section: Comparison With Experimental Datamentioning

confidence: 99%

Section: Comparison With Experimental Datamentioning

confidence: 99%

Section: Comparison With Experimental Datamentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

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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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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