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

Laginja, Iva; Soummer, Rémi; Mugnier, Laurent M.; Pueyo, Laurent; Sauvage, Jean-François; Leboulleux, Lucie; Coyle, Laura; Knight, J. Scott

doi:10.1117/1.jatis.7.1.015004

Cited by 25 publications

(47 citation statements)

References 79 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…This raises the necessity for modeling, performance prediction and tolerancing tools that are not dependent on testing of the fully integrated observatory system. The PASTIS tolerancing tool, presented in theory so far (Laginja et al 2021;Leboulleux et al 2018b), provides us with methods to derive segment stability tolerances that in turn will determine the coronagraphic performance of an imaging instrument like those on LUVOIR. In this paper, we perform the first hardware validation of an experimentally calibrated tolerancing model.…”

Section: Discussionmentioning

confidence: 99%

“…We can see in Fig. 7 that this puts a c significantly off the knee around the coronagraph floor, which was discussed as an optimal regime for a c in Laginja et al (2021). This was done in order to increase the signal-to-noise ratio (S/N) in the fringe images during the matrix calibration, while simultaneously not increasing a c too much along the linear aberration regime indicated in Fig.…”

Section: Matrix Measurementmentioning

confidence: 94%

“…In the following section, we present a brief summary of the PASTIS tolerancing model (Laginja et al 2021), and expand it to include a drifting coronagraph floor arising from time-dependent aberrations from sources other than the segmented mirror.…”

Section: Pastis Tolerancing Model and Extension To A Drifting Coronagraph Floormentioning

confidence: 99%

“…The tolerancing problem of segmented high-contrast instruments has been previously addressed with the Pair-based Analytical model for Segmented Telescope Imaging from Space (PASTIS; Laginja et al 2021;Laginja et al 2020;Laginja et al 2019;Leboulleux et al 2018bLeboulleux et al ,a, 2017b. It is an analytical model that calculates the average contrast in the DH caused by pupilplane segment misalignments using a simple matrix multiplication.…”

Section: Introductionmentioning

confidence: 99%

“…In this paper we use the semi-analytical development of the PASTIS model (Laginja et al 2021(Laginja et al , 2019 to measure an experimental PASTIS matrix on the HiCAT testbed (Soummer et al 2018;Moriarty et al 2018;Leboulleux et al 2016Leboulleux et al , 2017aN'Diaye et al , 2014N'Diaye et al , 2013 by replacing the images usually provided by an end-to-end simulator with laboratory measurements. We then use this experimental PASTIS matrix for further analysis, meaning the validation of the instantaneous forward model for the calculation of the average DH contrast and WFE tolerancing analysis, and compare the results to a simulated case.…”

Section: Introductionmentioning

confidence: 99%

See 4 more Smart Citations

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

Laginja

Sauvage

Mugnier

et al. 2022

A&A

Self Cite

View full text Add to dashboard Cite

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.

show abstract

Section: Discussionmentioning

confidence: 99%

Section: Matrix Measurementmentioning

confidence: 94%

Section: Pastis Tolerancing Model and Extension To A Drifting Coronagraph Floormentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

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

Laginja

Sauvage

Mugnier

et al. 2022

A&A

Self Cite

View full text Add to dashboard Cite

show abstract

Redundant apodization for direct imaging of exoplanets

Leboulleux¹,

Carlotti²,

N’Diaye

2022

A&A

Self Cite

View full text Add to dashboard Cite

Context. Direct imaging and spectroscopy of Earth-like planets and young Jupiters require contrast values up to 10 6 − 10 10 at angular separations of a few dozen milliarcseconds. To achieve this goal, one of the most promising approaches consists of using large segmented primary mirror telescopes with coronagraphic instruments. While they are able to reach high contrast at small angular separations, coronagraphs are highly sensitive to wavefront errors, however. The segmentation itself is responsible for phasing errors and segment-level vibrations that have to be controlled at a subnanometric accuracy. Aims. We propose an innovative method for a coronagraph design that allows a consequent relaxation of the segment phasing and stability constraints for low segment-count mirrors and generates an instrument that is more robust to segment-level wavefront errors. Methods. This method is based on an optimization of the coronagraph design that includes a segment-level apodization. This is repeated over the pupil to match the segmentation redundancy and improves the contrast stability beyond the minimum separation set by the single-segment diffraction limit. Results. We validate this method on a Giant Magellan Telescope (GMT)-like pupil (seven circular segments) for two coronagraph types: apodized pupil Lyot coronagraphs, and apodizing phase plate coronagraphs. For the apodized pupil Lyot coronagraphs, redundant apodization enables releasing the piston phasing constraints by a factor of 5 to 20 compared to classical designs. For the apodizing phase plate coronagraphs, the contrast remains almost constant up to 1 radian RMS of the phasing errors. We also show that redundant apodizations increase the robustness of the coronagraph to segment tip-tilt errors, as well as to missing segment errors. Conclusions. Redundant apodization enables reducing or even removing any constraints on the primary mirror segment phasing at the price of larger angular separations and lower throughputs. This method cannot be applied to higher-segment count mirrors such as the ELT or the TMT, but it is particularly suitable for low segment-count mirrors (fewer than ∼ 20 segments) such as the GMT aperture. These mirrors aim for high-contrast imaging of debris disks or exoplanets down to 100 mas.

show abstract

Redundant apodization for direct imaging of exoplanets

Leboulleux

Carlotti

N’Diaye

et al. 2022

A&A

Self Cite

View full text Add to dashboard Cite

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.

show abstract

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

Cited by 25 publications

References 79 publications

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

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

Redundant apodization for direct imaging of exoplanets

Redundant apodization for direct imaging of exoplanets

Contact Info

Product

Resources

About