The active phasing experiment: Part I. Concept and objectives

Yaitskova, Natalia; Gonté, Frederic; Dérie, F.; Noethe, L.; Surdej, Isabelle; Karban, Robert; Dohlen, Kjetil; Langlois, M.; Esposito, Simone; Pinna, Enrico; Reyes, M.; Montoya, Luzma; Terrett, D. L.

doi:10.1117/12.671189

Cited by 19 publications

(6 citation statements)

References 11 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In any on-sky application, the calibration matrix is conventionally measured using either an internal calibration source or a stellar target. A pseudo-synthetic calibration matrix can also be built by experimentally measuring the estimators on a single segment and replicating them in all the other segments in the matrix structure deduced from simulations (e.g., Yaitskova et al 2006). While straightforward when looking at a reasonable number of segments, the calibration matrix is avoidable by using an alternative method based on the ZELDA signal normalization.…”

Section: Calibration and Propertiesmentioning

confidence: 99%

See 1 more Smart Citation

Fine cophasing of segmented aperture telescopes with ZELDA, a Zernike wavefront sensor in the diffraction-limited regime

Janin-Potiron

N’Diaye

Martínez

et al. 2017

A&A

View full text Add to dashboard Cite

Context. Segmented aperture telescopes require an alignment procedure with successive steps from coarse alignment to monitoring process in order to provide very high optical quality images for stringent science operations such as exoplanet imaging. The final step, referred to as fine phasing, calls for a high sensitivity wavefront sensing and control system in a diffraction-limited regime to achieve segment alignment with nanometric accuracy. In this context, Zernike wavefront sensors represent promising options for such a calibration. A concept called the Zernike unit for segment phasing (ZEUS) was previously developed for ground-based applications to operate under seeing-limited images. Such a concept is, however, not suitable for fine cophasing with diffraction-limited images. Aims. We revisit ZELDA, a Zernike sensor that was developed for the measurement of residual aberrations in exoplanet direct imagers, to measure segment piston, tip, and tilt in the diffraction-limited regime. Methods. We introduce a novel analysis scheme of the sensor signal that relies on piston, tip, and tilt estimators for each segment, and provide probabilistic insights to predict the success of a closed-loop correction as a function of the initial wavefront error. Results. The sensor unambiguously and simultaneously retrieves segment piston and tip-tilt misalignment. Our scheme allows for correction of these errors in closed-loop operation down to nearly zero residuals in a few iterations. This sensor also shows low sensitivity to misalignment of its parts and high ability for operation with a relatively bright natural guide star. Conclusions. Our cophasing sensor relies on existing mask technologies that make the concept already available for segmented apertures in future space missions.

show abstract

Section: Calibration and Propertiesmentioning

confidence: 99%

“…Among these concepts, we here consider the Zernike wavefront sensor (ZWFS), which is based on the phase-contrast method (Zernike 1934). These concepts aim to modulate phase aberrations on an unresolved star image with a phase-shifting mask into intensity variations in a pupil plane.…”

Section: Introductionmentioning

confidence: 99%

Fine cophasing of segmented aperture telescopes with ZELDA, a Zernike wavefront sensor in the diffraction-limited regime

Janin-Potiron

N’Diaye

Martínez

et al. 2017

A&A

View full text Add to dashboard Cite

show abstract

“…In the last years new cophasing techniques have been studied and developed. APE 4 is an experiment which integrates and validates non-adaptive wavefront control schemes and technologies for an ELT. This includes: i) Evaluating and comparing the performance of four phasing wavefront sensors: DIPSI, PYPS 5 , SHAPS 6 and ZEUS 7 , in the laboratory and on-sky; ii) Integrating segmented aperture control into an active system, and driving both the active system and the segments control system from the output of the system.…”

Section: Introductionmentioning

confidence: 99%

DIPSI: the diffraction image phase sensing instrument for APE

et al. 2006

Self Cite

View full text Add to dashboard Cite

Large segmented mirrors require efficient co-phasing techniques in order to avoid the image degradation due to segments misalignment. For this purpose in the last few years new co-phasing techniques have been developed in collaboration with several European institutes. The Active Phasing Experiment (APE) will be a technical instrument aimed at testing different phasing techniques for an Extremely Large Telescope (ELT). A mirror composed of 61 hexagonal segments will be conjugated to the primary mirror of the VLT 1 (Very Large Telescope). Each segment can be moved in piston, tip and tilt. Three new types of co-phasing sensors dedicated to the measurement of segmentation errors will be tested, evaluated and compared: ZEUS (Zernike Unit for Segment phasing) developed by LAM and IAC, PYPS (PYramid Phase Sensor) developed by INAF/ARCETRI, and DIPSI (Diffraction Image Phase Sensing Instrument) developed by IAC, GRANTECAN and LAM. This experiment will first run in the laboratory with pointlike polychromatic sources and a turbulence generator. In a second step, it will be mounted at the Nasmyth platform focus of a VLT unit telescope. This paper describes the scientific concept of DIPSI, its optomechanical design, the signal analysis to retrieve segment piston and tip-tilt, the multiwavelength algorithm to increase the capture range, and the multiple segmentation case, including both simulation and laboratory tests results.

show abstract

“…Indeed usual Adaptive Optics (AO) systems are not suitable to detect directly piston aberrations, which is the most challenging task when cophasing segmented pupils. The Active Phasing Experiment [1][2][3] managed to compare four WFS Wavefront sensing for the European-ELT: a pyramid sensor, a curvature sensor, a phase filtering sensor and a ShackHartmann (SH) sensor. Each of them are modified versions of the usual sensors.…”

Section: Introductionmentioning

confidence: 99%

Focal-plane wavefront sensing for segmented telescope

Delavaquerie

Cassaing

Amans

2010

1st AO4ELT Conference - Adaptive Optics for Extremely Large Telescopes

View full text Add to dashboard Cite

Abstract. To achieve the ultimate resolution of future ELTs, the segments of their primary mirror must be aligned. This paper present focal plane (FP) wavefront sensing techniques that allow to perform piston measurements between the segments. Those techniques have the advantage of using images that are the result of the interference of all the segments. This makes FP measurements capable of handling complex apertures. New developments at ONERA allow us to apply FP measurements for different applications. We present an upgrade of the usual Shack-Hartmann pairwise technique. We also show that phase diversity is able to cophase an ELT. Eventually, we show our current developments in term of analytical algorithms and our new bench, NIRTA, which is under integration at ONERA.

show abstract

The active phasing experiment: Part I. Concept and objectives

Cited by 19 publications

References 11 publications

Fine cophasing of segmented aperture telescopes with ZELDA, a Zernike wavefront sensor in the diffraction-limited regime

Fine cophasing of segmented aperture telescopes with ZELDA, a Zernike wavefront sensor in the diffraction-limited regime

DIPSI: the diffraction image phase sensing instrument for APE

Focal-plane wavefront sensing for segmented telescope

Contact Info

Product

Resources

About