Implementation of a broadband focal plane estimator for high-contrast dark zones

Redmond, Susan; Pueyo, Laurent; Pogorelyuk, Leonid; Noss, James; Will, Scott D.; Laginja, Iva; Kasdin, N. Jeremy; Perrin, Marshall D.; Soummer, Rémi

doi:10.1117/12.2594620

Cited by 4 publications

(4 citation statements)

References 12 publications

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“…6 HiCAT can achieve contrast levels of 2.5 × 10 −8 (6.5 × 10 −8 90% of the time) using the monochromatic laser source and 6.3 × 10 −7 over a 20 nm band using the broadband laser source. 7 Here, we demonstrate maintenance of the dark zone contrast in the presence of a wavefront error drift at monochromatic levels of 2.5 × 10 −8 (IrisAO drift) and 5.9 × 10 −8 (all DMs drift), as well as 7.0 × 10 −7 at multiple wavelengths (BMC drift). This work is an extension of Redmond et al 2020 8 and Pogorelyuk et al 2019 9 which can be referred to for additional background and results.…”

mentioning

confidence: 57%

Dark zone maintenance results for segmented aperture wavefront error drift in a high contrast space coronagraph

Redmond¹,

Pueyo²,

Pogorelyuk³

et al. 2021

Preprint

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Due to the limited number of photons, directly imaging planets requires long integration times with a coronagraphic instrument. The wavefront must be stable on the same time scale, which is often difficult in space due to thermal variations and other mechanical instabilities. In this paper, we discuss the implications on future space mission observing conditions of our recent laboratory demonstration of a dark zone maintenance (DZM) algorithm. The experiments are performed on the High-contrast imager for Complex Aperture Telescopes (HiCAT) at the Space Telescope Science Institute (STScI). The testbed contains a segmented aperture, a pair of continuous deformable mirrors (DMs), and a lyot coronagraph. The segmented aperture injects high order wavefront aberration drifts into the system which are then corrected by the DMs downstream via the DZM algorithm. We investigate various drift modes including segmented aperture drift, all three DMs drift simultaneously, and drift correction at multiple wavelengths.

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mentioning

confidence: 57%

Dark zone maintenance results for segmented aperture wavefront error drift in a high contrast space coronagraph

Redmond¹,

Pueyo²,

Pogorelyuk³

et al. 2021

Preprint

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“…In the context of dark hole maintenance, standard single-pixel pairwise probing and EFC (dotted orange line) have three tunable parameters: probe magnitude, EFC regularization (α EFC ), and the optional estimator regularization (α). 30 The method proposed in Sec. 2.2 (thin green line) has just two tunable parameters: probe magnitude and α. Perfect-knowledge EFC (thick blue line) would only require one parameter, α EFC , since there is no estimation involved.…”

Section: Wavefront Control Resultsmentioning

confidence: 99%

“…Using α > 0 in single-pixel estimation could potentially improve the closed-loop contrast in the low photon-flux regime. 30 However, the method proposed in Sec. 2.2 is more elegant and easier to calibrate as it requires fewer regularization parameters, α instead of both α and α EFC .…”

Section: Wavefront Control Resultsmentioning

confidence: 99%

Dark hole maintenance with modal pairwise probing in numerical simulations of Roman coronagraph instrument

Pogorelyuk

Krist

Nemati

et al. 2022

J. Astron. Telesc. Instrum. Syst.

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We propose an efficient approach for focal-plane wavefront estimation for highcontrast imaging. It is designed for very low photon flux regimes with the Roman Space Telescope Coronagraph Instrument in mind. During days-long exposures of Roman, the starlight wavefront will drift due to the thermal instabilities of the optical tube assembly (OTA) and deformable mirror (DM) actuators. To correct the drift in high-order spatial wavefront modes, Roman will periodically be pointed to a bright reference star to sense the speckles in the dark hole (the high-contrast region of the image) and correct them. However, this maneuver decreases observation time by several hours a day and may lead to wavefront instability by causing structural and thermal stresses on the OTA. Instead, we propose maintaining the dark hole using the DM to modulate (probe) the speckles while observing the target star. Our proposed algorithm can then be used to directly estimate the DM commands that would create such speckles, rather than first estimating the electric field of the speckles. Applying the opposite commands on the DM reduces the intensity of the speckles without slewing to the reference star. Further, we analyze this dark-hole maintenance approach using data from Roman Observing Scenario 9 (OS9) simulations while assuming that the high-order wavefront control on Roman will be carried out from the Earth (ground-in-the-loop). In our simulations of Roman's Hybrid Lyot Coronagraph, the high-order wavefront errors were sensed and corrected while observing a dim target, 47 UMa. Despite the DM probes, the photon flux in the dark hole remained close to that in OS9 and well below detector noise. In terms of planet-detectability, dark hole maintenance kept the postprocessing contrast within 10% of OS9's, even after pointing the telescope at the target star for 6 days. The OTA stability that dark hole maintenance provides compared to slewing the telescope potentially outweighs the small negative impact it has on the contrast.

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“…Various other implementations of PWP have been developed, including extensions to broadband estimation 17 and implementations of a Kalman filter for improved estimation, 18 but all rely on the difference images from pairwise probes.…”

Section: Definitions and Algorithmsmentioning

confidence: 99%

Modeling and performance analysis of implicit electric field conjugation with two deformable mirrors applied to the Roman Coronagraph

Milani,

Douglas,

Haffert

et al. 2024

J. Astron. Telesc. Instrum. Syst.

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High-order wavefront sensing and control (HOWFSC) is key to creating a dark hole region within the coronagraphic image plane where high contrasts are achieved. The Roman Coronagraph is expected to perform its HOWFSC with a ground-in-the-loop scheme due to the computational complexity of the electric field conjugation (EFC) algorithm. This scheme provides the flexibility to alter the HOWFSC algorithm for given science objectives. The baseline HOWFSC scheme involves running EFC while observing a bright star such as ζ Puppis to create the initial dark hole followed by a slew to the science target. The new implicit EFC (iEFC) algorithm removes the optical diffraction model from the controller, making the final contrast independent of model accuracy. While previously demonstrated with a single deformable mirror, iEFC is extended to two deformable mirror systems to create annular dark holes. First, an overview of both EFC and iEFC is presented. The algorithm is then applied to the wide-field-of-view shaped pupil coronagraph (SPC-WFOV) mode designed for the Roman Space Telescope using end-to-end physical optics models. Initial noiseless monochromatic simulations demonstrate the efficacy of iEFC as well as the optimal choice of modes for the SPC-WFOV instrument. Further simulations with a 3.6% wavefront control bandpass and a broader 10% bandpass then demonstrate that iEFC can be used in broadband scenarios to achieve contrasts below 10 −8 with Roman. Finally, an electron multiplying charge-coupled device (EMCCD) model is implemented to estimate calibration times and predict the controller's performance. Here, 10 −8 contrasts are achieved with a calibration time of ∼6.8 h assuming the reference star is ζ Puppis. The results here indicate that iEFC can be a valid HOWFSC method that can mitigate the risk of model errors associated with spaceborne coronagraphs, but to maximize iEFC performance, lengthy calibration times will be required to mitigate the noise accumulated during calibration.

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Implementation of a broadband focal plane estimator for high-contrast dark zones

Cited by 4 publications

References 12 publications

Dark zone maintenance results for segmented aperture wavefront error drift in a high contrast space coronagraph

Dark zone maintenance results for segmented aperture wavefront error drift in a high contrast space coronagraph

Dark hole maintenance with modal pairwise probing in numerical simulations of Roman coronagraph instrument

Modeling and performance analysis of implicit electric field conjugation with two deformable mirrors applied to the Roman Coronagraph

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