Method for deriving optical telescope performance specifications for Earth-detecting coronagraphs

Nemati, Bijan; Stahl, H. Philip; Stahl, Mark T.; Ruane, Garreth; Sheldon, Leah J.

doi:10.1117/1.jatis.6.3.039002

Cited by 24 publications

(41 citation statements)

References 32 publications

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“…We begin with a simple Brownian Motion (Durrett (2019)) model for the evolution of high-order WFE modes in the context of space based coronagraphs. This assumption leads to linear growth of uncertainty in the intensityan approximation that is commonly used when evaluating exoplanet detection performance (Nemati et al (2020)). Formally, the r WFE mode coefficients, k = (k • t s ) ∈ R r , are such that their increments are normally (and independently) distributed with some drift covariance…”

Section: Wfe Modes Driftmentioning

confidence: 99%

Information-theoretical Limits of Recursive Estimation and Closed-loop Control in High-contrast Imaging

Pogorelyuk,

Pueyo,

Males

et al. 2021

Preprint

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A lower bound on unbiased estimates of wavefront errors (WFE) is presented for the linear regime of small perturbation and active control of a high-contrast region (dark hole). Analytical approximations and algorithms for computing the closed-loop covariance of the WFE modes are provided for discrete-and continuous-time linear WFE dynamics. Our analysis applies to both image-plane and non-common-path wavefront sensing (WFS) with Poisson-distributed measurements and noise sources (i.e., photon-counting mode). Under this assumption, we show that recursive estimation benefits from infinitesimally short exposure times, is more accurate than batch estimation and, for high-order WFE drift dynamical processes, scales better than batch estimation with amplitude and star brightness. These newly-derived contrast scaling laws are a generalization of previously known theoretical and numerical results for turbulence-driven Adaptive Optics. For space-based coronagraphs, we propose a scheme for combining models of WFE drift, low-order non-common-path WFS (LOWFS) and highorder image-plane WFS (HOWFS) into closed-loop contrast estimates. We also analyze the impact of residual low-order WFE, sensor noise, and other sources incoherent with the star, on closed-loop dark-hole maintenance and the resulting contrast. As an application example, our model suggests that the Roman Space Telescope might operate in a regime that is dominated by incoherent sources rather than WFE drift, where the WFE drift can be actively rejected throughout the observations with residuals significantly dimmer than the incoherent sources. The models proposed in this paper make possible the assessment of the closed-loop contrast of coronagraphs with combined LOWFS and HOWFS capabilities, and thus help estimate WFE stability requirements of future instruments.

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Section: Wfe Modes Driftmentioning

confidence: 99%

Information-theoretical Limits of Recursive Estimation and Closed-loop Control in High-contrast Imaging

Pogorelyuk,

Pueyo,

Males

et al. 2021

Preprint

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“…Figure 3 shows the core throughput for three coronagraphs (vector-vortex coronagraph charge 4 (VVC-4), charge 6 (VVC-6), and hybrid Lyot (HLC) with the HabEx baseline 4-m, off-axis, unobscured telescope) and the throughput for a 6-m, on-axis, segmented PM telescope (Segm) (e.g., the James Webb Space Telescope, JWST) with an apodized pupil Lyot coronagraph (APLC). 5,6 Regarding minimum aperture and diffraction limit, the specification is based on a design reference mission (DRM) yield estimate for an off-axis-telescope/coronagraph combination. 7 Threshold science occurs when the telescope PSF core radius (λ∕D) is <25 mas.…”

Section: Ota Specificationsmentioning

confidence: 99%

“…Vertical line is Exo-Earth at 10 pc (100 mas). 5,6 because the PM is larger and less stiff than the SM or TM, it gets the largest allocation. Note that the measured Wide Field Infrared Survey Telescope (WFIRST) PM WFE is 13.2 nm rms.…”

Section: Diffraction-limited Performancementioning

confidence: 99%

Habitable-Zone Exoplanet Observatory baseline 4-m telescope: systems-engineering design process and predicted structural thermal optical performance

Stahl

Kuan

Arnold

et al. 2020

J. Astron. Telesc. Instrum. Syst.

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The Habitable-Zone Exoplanet Observatory Mission (HabEx) is one of four large missions under review for the 2020 astrophysics decadal survey. Its goal is to directly image and spectroscopically characterize planetary systems in the habitable zone around nearby Sun-like stars. In addition, HabEx will perform a broad range of general astrophysics science enabled by a 115-to 1700-nm spectral range and 3 × 3 arcminute field of view. Critical to achieving its science goals, HabEx requires a large, ultrastable UV/optical/near-IR telescope. Using sciencedriven systems engineering, HabEx specified its baseline telescope to be a 4-m off-axis, unobscured three-mirror anastigmatic architecture with diffraction-limited performance at 400 nm, and wavefront stability on the order of a few tens of picometers. We summarize the systems-engineering approach to the baseline telescope assembly's optomechanical design, including a discussion of how science requirements drive the telescope's specifications. We also present structural thermal optical performance analysis showing that the baseline telescope structure meets its specified tolerances. We report new and updated analysis that is not in the HabEx final report. © The Authors. Published by SPIE under a Creative Commons Attribution 4.0 Unported License. Distribution or reproduction of this work in whole or in part requires full attribution of the original publication, including its DOI.

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“…The extreme contrast levels that are needed for the detection of exoEarths require excellent stability against wavefront errors (WFEs) over a range of temporal and spatial frequencies (Pueyo et al 2019;Coyle et al 2019;Feinberg et al 2017). While some of these can be actively controlled with a WFS&C system, or do not have a large impact on the contrast due to robust coronagraph designs, aberration modes to which the instrument is very sensitive must be held to a minimal level (Nemati et al 2020;Juanola-Parramon et al 2019;Nemati et al 2017). Typically, it is enough to control these misalignment modes on the timescales of the WFS&C system.…”

Section: Introductionmentioning

confidence: 99%

Wavefront tolerances of space-based segmented telescopes at very high contrast: Experimental validation

Laginja

Sauvage

Mugnier

et al. 2022

A&A

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Context. The detection and characterization of Earth-like exoplanets (exoEarths) from space requires exquisite wavefront stability at contrast levels of 10−10. On segmented telescopes in particular, aberrations induced by co-phasing errors lead to a light leakage through the coronagraph, deteriorating the imaging performance. These need to be limited in order to facilitate the direct imaging of exoEarths. Aims. We perform a laboratory validation of an analytical tolerancing model that allows us to determine wavefront error requirements in the 10−6 − 10−8 contrast regime for a segmented pupil with a classical Lyot coronagraph. We intend to compare the results to simulations, and we aim to establish an error budget for the segmented mirror on the High-contrast imager for Complex Aperture Telescopes (HiCAT) testbed. Methods. We use the Pair-based Analytical model for Segmented Telescope Imaging from Space to measure a contrast influence matrix of a real high-contrast instrument, and use an analytical model inversion to calculate per-segment wavefront error tolerances. We validate these tolerances on the HiCAT testbed by measuring the contrast response of segmented mirror states that follow these requirements. Results. The experimental optical influence matrix is successfully measured on the HiCAT testbed, and we derive individual segment tolerances from it that correctly yield the targeted contrast levels. Further, the analytical expressions that predict a contrast mean and variance from a given segment covariance matrix are confirmed experimentally.

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Method for deriving optical telescope performance specifications for Earth-detecting coronagraphs

Cited by 24 publications

References 32 publications

Information-theoretical Limits of Recursive Estimation and Closed-loop Control in High-contrast Imaging

Information-theoretical Limits of Recursive Estimation and Closed-loop Control in High-contrast Imaging

Habitable-Zone Exoplanet Observatory baseline 4-m telescope: systems-engineering design process and predicted structural thermal optical performance

Wavefront tolerances of space-based segmented telescopes at very high contrast: Experimental validation

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