System study of EPICS: the exoplanets imager for the E-ELT

Vérinaud, Christophe; Kasper, Markus; Beuzit, Jean-Luc; Gratton, R.; Mesa, D.; Aller-Carpentier, Emmanuel; Fedrigo, Enrico; Abe, Lyu; Baudoz, Pierre; Boccaletti, A.; Bonavita, M.; Dohlen, Kjetil; Hubin, N.; Kerber, F.; Korkiakoski, Visa; Antichi, J.; Martínez, P.; Rabou, Patrick; Roelfsema, R.; Schmid, Hans Martin; Thatte, Niranjan; Salter, G.; Tecza, Matthias; Venema, Lars; Hanenburg, Hiddo; Jäger, R.; Yaitskova, Natalia; Preis, Olivier; Orecchia, Mélanie; Stadler, Eric

doi:10.1117/12.857096

Cited by 14 publications

(10 citation statements)

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“…limited by edge diffraction effects, but these effects are no worse than Fresnel ringing and can thus be mitigated using optical designs which are now routinely used in high contrast instruments (see Vérinaud et al (2010) for such discussions). For the remainder of this paper we thus assume the diffractive artifacts have been adequately mitigated and we compute our results assuming a geometric propagation between DM1 and DM2.…”

Section: Discussionmentioning

confidence: 99%

“…Such instruments will reach the contrast required to achieve their scientific goals by combining Extreme Adaptive Optics systems (Ex-AO, Poyneer & Véran (2005)), optimized coronagraphs Guyon 2003;Rouan et al 2000) and nanometer class wavefront calibration (Sauvage et al 2007;Wallace et al 2009;Pueyo et al 2010). In the future, highcontrast instruments on Extremely Large Telescopes will focus on probing planetary formation in distant star email: lap@pha.jhu.edu 1 Department of Physics and Astronomy, Johns Hopkins University, Baltimore, MD, USA forming regions (Macintosh et al 2006), characterizing both the spectra of cooler gas giants (Vérinaud et al 2010) and the reflected light of planets in the habitable zone of low mass stars. The formidable contrast necessary to investigate the presence of biomarkers at the surface of earth analogs (> 10 10 ) cannot be achieved from the ground beneath atmospheric turbulence and will require dedicated space-based instruments .…”

Section: Introductionmentioning

confidence: 99%

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High-Contrast Imaging With an Arbitrary Aperture: Active Compensation of Aperture Discontinuities

Pueyo

Norman

2013

ApJ

104

108

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We present a new method to achieve high-contrast images using segmented and/or on-axis telescopes. Our approach relies on using two sequential Deformable Mirrors to compensate for the large amplitude excursions in the telescope aperture due to secondary support structures and/or segment gaps. In this configuration the parameter landscape of Deformable Mirror Surfaces that yield high contrast Point Spread Functions is not linear, and non-linear methods are needed to find the true minimum in the optimization topology. We solve the highly non-linear Monge-Ampere equation that is the fundamental equation describing the physics of phase induced amplitude modulation. We determine the optimum configuration for our two sequential Deformable Mirror system and show that high-throughput and high contrast solutions can be achieved using realistic surface deformations that are accessible using existing technologies. We name this process Active Compensation of Aperture Discontinuities (ACAD). We show that for geometries similar to JWST, ACAD can attain at least 10 −7 in contrast and an order of magnitude higher for both the future Extremely Large Telescopes and on-axis architectures reminiscent of HST. We show that the converging non-linear mappings resulting from our Deformable Mirror shapes actually damp near-field diffraction artifacts in the vicinity of the discontinuities. Thus ACAD actually lowers the chromatic ringing due to diffraction by segment gaps and strut's while not amplifying the diffraction at the aperture edges beyond the Fresnel regime. This outer Fresnel ringing can be mitigated by properly designing the optical system. Consequently, ACAD is a true broadband solution to the problem of high-contrast imaging with segmented and/or on-axis apertures. We finally show that once the non-linear solution is found, fine tuning with linear methods used in wavefront control can be applied to further contrast by another order of magnitude. Generally speaking, the ACAD technique can be used to significantly improve a broad class of telescope designs for a variety of problems.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

High-Contrast Imaging With an Arbitrary Aperture: Active Compensation of Aperture Discontinuities

Pueyo

Norman

2013

ApJ

104

108

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“…However, when the number of optimization parameters is increased, the computational requirements generally rise unacceptably fast. The high computational costs are problematic for instance in astronomy; the largest future adaptive optics system is envisioned to have a wavefront corrector of a size of 200 × 200 [8].…”

Section: Introductionmentioning

confidence: 99%

Fast & Furious focal-plane wavefront sensing

et al. 2014

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We present two complementary algorithms suitable for using focal-plane measurements to control a wavefront corrector with an extremely high-spatial resolution. The algorithms use linear approximations to iteratively minimize the aberrations seen by the focal-plane camera. The first algorithm, Fast & Furious (FF), uses a weak-aberration assumption and pupil symmetries to achieve fast wavefront reconstruction. The second algorithm, an extension to FF, can deal with an arbitrary pupil shape; it uses a Gerchberg-Saxton (GS)-style error reduction to determine the pupil amplitudes. Simulations and experimental results are shown for a spatial-light modulator controlling the wavefront with a resolution of 170 × 170 pixels. The algorithms increase the Strehl ratio from ∼0.75 to 0.98-0.99, and the intensity of the scattered light is reduced throughout the whole recorded image of 320 × 320 pixels. The remaining wavefront rms error is estimated to be ∼0.15 rad with FF and ∼0.10 rad with FF-GS.

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“…As for the 8-m class Extreme AO instruments, the 30-m class Extreme AO instruments will also be able to measure cloud colors only down to a level ultimately limited by systematic trends in the photometry, due to the instrumental changes, atmospheric variations, etc. The most significant improvement of the 30-m Extreme AO over the 8-m Extreme AO instruments will be in their ability to do moderate-resolution (R ∼ 100 -1000) spectroscopy both in the near IR with an Integral Field Spectrograph (IFS) on ELT/EPICS, TMT/NFIRAOS and GMT/NIRExAO Imager (Vérinaud et al 2010;Herriot et al 2006;Johns 2008) and in the mid-IR using, for example, instruments like GMT/TIGER in the 8 to 20 µm wavelength coverage (Jaffe et al 2010). Further improvements will come in the form of polarimetric measurements and the extended time-domain probed with the faster cadence, allowing detection of smaller-scale variations.…”

Section: -M Class Telescopes With Next-generation Extreme Ao (30m+ mentioning

confidence: 99%

Mapping Directly Imaged Giant Exoplanets

Kostov

Apai

2012

ApJ

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With the increasing number of directly imaged giant exoplanets the current atmosphere models are often not capable of fully explaining the spectra and luminosity of the sources. A particularly challenging component of the atmosphere models is the formation and properties of condensate cloud layers, which fundamentally impact the energetics, opacity, and evolution of the planets.Here we present a suite of techniques that can be used to estimate the level of rotational modulations these planets may show. We propose that the timeresolved observations of such periodic photometric and spectroscopic variations of extrasolar planets due to their rotation can be used as a powerful tool to probe the heterogeneity of their optical surfaces. In this paper we develop simulations to explore the capabilities of current and next-generation ground-and space-based instruments for this technique. We address and discuss the following questions: a) what planet properties can be deduced from the light curve and/or spectra, and in particular can we determine rotation periods, spot-coverage, spot colors, spot spectra; b) what is the optimal configuration of instrument/wavelength/temporal sampling required for these measurements; and, c) can principal component analysis be used to invert the light curve and deduce the surface map of the planet.1 To whom correspondence should be addressed. Email: vkostov@pha.jhu.edu -2 -Our simulations describe the expected spectral differences between homogeneous (clear or cloudy) and patchy atmospheres, outline the significance of the dominant absorption features of H 2 O, CH 4 , and CO and provide a method to distinguish these two types of atmospheres. Assuming surfaces with and without clouds for most currently imaged planets the current models predict the largest variations in the J-band. Simulated photometry from current and future instruments is used to estimate the level of detectable photometric variations. We conclude that future instruments will be able to recover not only the rotation periods, cloud cover, cloud colors and spectra but even cloud evolution. We also show that a longitudinal map of the planet's atmosphere can be deduced from its disk-integrated light curves.

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System study of EPICS: the exoplanets imager for the E-ELT

Cited by 14 publications

References 0 publications

High-Contrast Imaging With an Arbitrary Aperture: Active Compensation of Aperture Discontinuities

High-Contrast Imaging With an Arbitrary Aperture: Active Compensation of Aperture Discontinuities

Fast & Furious focal-plane wavefront sensing

Mapping Directly Imaged Giant Exoplanets

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