Wavefront error tolerancing for direct imaging of exo-Earths with a large segmented telescope in space

Laginja, Iva; Leboulleux, Lucie; Pueyo, Laurent; Soummer, Rémi; Sauvage, Jean-François; Mugnier, Laurent M.; Coyle, Laura; Knight, J. Scott; Laurent, Kathryn St.; Por, Emiel H.; Noss, James

doi:10.1117/12.2530300

Cited by 10 publications

(10 citation statements)

References 26 publications

(29 reference statements)

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“…For segmented telescopes equipped with high-contrast imagers, the Pair-based Analytical model for Segmented Telescopes Imaging from Space (PASTIS Leboulleux et al 2018;Laginja & Leboulleux 2019;Laginja et al 2021) provides an expression for the intensity in the coronagraphic dark hole as a function of the segment-level phase errors. For a symmetric dark zone with amplitude aberrations and phase aberrations after the focal plane mask of the coronagraph neglected, then the intensity in the dark zone I can be expressed as…”

Section: Review Of Redundant Apodized Pupilsmentioning

confidence: 99%

Redundant apodization for direct imaging of exoplanets

Leboulleux

Carlotti

N’Diaye

et al. 2022

A&A

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Context. Telescope pupil fragmentation from spiders generates specific aberrations that have been observed at various telescopes and are expected on the 30-meter class telescopes under construction. This is known as the island effect, and it induces differential pistons, tips, and tilts on the pupil petals, deforming the instrumental point spread function (PSF); it is one of the main limitations to the direct detection of exoplanets with high-contrast imaging. These petal-level aberrations can have different origins such as the low-wind effect or petaling errors in the adaptive optics reconstruction. Aims. In this paper we propose a method for alleviating the impact of the aberrations induced by island effects on high-contrast imaging by adapting the coronagraph design in order to increase its robustness to petal-level aberrations. Methods. Following a method first developed and applied on robustness to errors due to primary mirror segmentation (e.g., segment phasing errors, missing segments), we developed and tested redundant apodized pupils (RAP): apodizers designed at the petal-scale, then duplicated and rotated to mimic the pupil petal geometry. Results. We applied this concept to the ELT architecture, made of six identical petals, to yield a 10 −6 contrast in a dark region from 8 to 40λ/D. Both amplitude and phase apodizers proposed in this paper are robust to differential pistons between petals, with minimal degradation to their coronagraphic PSFs and contrast levels. In addition, they are also more robust to petal-level tip-tilt errors than classical apodizers designed for the whole pupil, with which the limit of contrast of 10 −6 in the coronagraph dark zone is achieved for constraints up to 2 rad RMS of these petal-level modes. Conclusions. In this paper the RAP concept proves its robustness to island effects (low-wind effect and post-adaptive optics petaling), with an application to the ELT architecture. It can also be considered for other 8-to 30-meter class ground-based units such as VLT/SPHERE, Subaru/SCExAO, GMT/GMagAO-X, and TMT/PSI.

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Section: Review Of Redundant Apodized Pupilsmentioning

confidence: 99%

Redundant apodization for direct imaging of exoplanets

Leboulleux

Carlotti

N’Diaye

et al. 2022

A&A

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“…PASTIS [9][10][11][12][13] is an analytical forward model that directly calculates the average contrast over the DH, a scalar quantity, from a set of segment-level aberration amplitudes in the pupil plane. Central to this model is the PASTIS matrix M , which describes the contrast contributions of an aberrated segment pair.…”

Section: Pastis Model Summarymentioning

confidence: 99%

“…The ability to calculate this information (independent segment requirements, analytical mean contrast and variance derivation) describes the statistical response of a segmented coronagraph to segment-level cophasing errors. In this paper, we use the semi-analytical development of the PASTIS model 12,13 to calculate a PASTIS matrix with an emulated HiCAT testbed, which we use for further analysis. In the following section, we present a brief summary of the tolerancing model.…”

Section: Pastis Model Summarymentioning

confidence: 99%

“…Previous studies have determined cophasing requirements for large segmented apertures to be on the order of 10 pm over the full pupil, 8 with the objective of maintaining a DH contrast of 10 −10 . Instead of defining WFE tolerances over the entire telescope pupil, the Pair-based Analytical model for Segmented Telescope Imaging from Space (PASTIS) [9][10][11][12] allows us to derive segment-specific requirements, either for each segment individually when they are statistically independent from each other, or in the form of a segment covariance matrix when there are correlations between them. 13 The next step is to perform an experimental validation of these segment-level tolerances on a segmented mirror of a high contrast instrument in a laboratory setting to seek confirmation that they indeed yield the coronagraphic contrast they were calculated for.…”

Section: Introductionmentioning

confidence: 99%

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Predicting contrast sensitivity to segmented aperture misalignment modes for the HiCAT testbed

Laginja,

Soummer,

Mugnier

et al. 2020

Preprint

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This paper presents the setup for empirical validations of the Pair-based Analytical model for Segmented Telescope Imaging from Space (PASTIS) tolerancing model for segmented coronagraphy. We show the hardware configuration of the High-contrast imager for Complex Aperture Telescopes (HiCAT) testbed on which these experiments will be conducted at an intermediate contrast regime between 10 −6 and 10 −8 . We describe the optical performance of the testbed with a classical Lyot coronagraph and describe the recent hardware upgrade to a segmented mode, using an IrisAO segmented deformable mirror. Implementing experiments on HiCAT is made easy through its top-level control infrastructure that uses the same code base to run on the real testbed, or to invoke the optical simulator. The experiments presented in this paper are run on the HiCAT testbed emulator, which makes them ready to be performed on actual hardware. We show results of three experiments with results from the emulator, with the goal to demonstrate PASTIS on hardware next. We measure the testbed PASTIS matrix, and validate the PASTIS analytical propagation model by comparing its contrast predictions to simulator results. We perform the tolerancing analysis on the optical eigenmodes (PASTIS modes) and on independent segments, then validate these results in respective experiments. This work prepares and enables the experimental validation of the analytical segment-based tolerancing model for segmented aperture coronagraphy with the specific application to the HiCAT testbed.

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“…We first introduce a new semi-analytical (SA) calculation method for the PASTIS matrix. 55 Then, we show how to compute the statistical mean of the contrast using the PASTIS modes and extend the model inversion to calculate segment-level WFE requirements for a given target contrast.…”

Section: Introductionmentioning

confidence: 99%

Analytical tolerancing of segmented telescope co-phasing for exo-Earth high-contrast imaging

Laginja

Soummer

Mugnier

et al. 2021

J. Astron. Telesc. Instrum. Syst.

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This paper introduces an analytical method to calculate segment-level wavefront error (WFE) tolerances to enable the detection of faint extra-solar planets using segmentedaperture telescopes in space. This study provides a full treatment of the case of spatially uncorrelated segment phasing errors for segmented telescope coronagraphy, which has so far only been approached using ad-hoc Monte Carlo (MC) simulations. Instead of describing the wavefront tolerance globally for all segments, our method produces spatially dependent requirement maps. We relate the statistical mean contrast in the coronagraph dark hole to the standard deviation of the WFE of each individual segment on the primary mirror. This statistical framework for segment-level tolerancing extends the Pair-based Analytical model for Segmented Telescope Imaging from Space (PASTIS), which is based uniquely on a matrix multiplication for the optical propagation. We confirm our analytical results with MC simulations of end-to-end optical propagations through a coronagraph. Comparing our results for the Apodized Pupil Lyot Coronagraph designs for the Large Ultraviolet Optical Infrared telescope to previous studies, we show general agreement but we provide a relaxation of the requirements for a significant subset of segments in the pupil. These requirement maps are unique to any given telescope geometry and coronagraph design. The spatially uncorrelated segment tolerances we calculate are a key element of a complete error budget that will also need to include allocations for correlated segment contributions. We discuss how the PASTIS formalism can be extended to the spatially correlated case by deriving the statistical mean contrast and its variance for a nondiagonal aberration covariance matrix. The PASTIS tolerancing framework therefore brings a new capability that is necessary for the global tolerancing of future segmented space observatories.

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Wavefront error tolerancing for direct imaging of exo-Earths with a large segmented telescope in space

Cited by 10 publications

References 26 publications

Redundant apodization for direct imaging of exoplanets

Redundant apodization for direct imaging of exoplanets

Predicting contrast sensitivity to segmented aperture misalignment modes for the HiCAT testbed

Analytical tolerancing of segmented telescope co-phasing for exo-Earth high-contrast imaging

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