On-Sky Speckle Nulling Demonstration at Small Angular Separation with SCExAO

Martinache, Frantz; Guyon, Olivier; Jovanović, Nemanja; Clergeon, Christophe; Singh, Garima; Kudo, Tomoyuki; Currie, Thayne; Thalmann, Christian; McElwain, Michael; Tamura, Motohide

doi:10.1086/677141

Cited by 85 publications

(65 citation statements)

References 26 publications

(32 reference statements)

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“…Most prominently, non-redundant aperture masking (NRM) interferometry (Tuthill et al 2000), relying on interferometric calibration tricks in the focal plane has led to high contrast detections (of the order of 1000:1) in a regime of angular separation (typically between 0.5 and a few λ/D) that is still unmatched in practice by techniques like coronagraphy (Kraus & Ireland 2012;Sallum et al 2015). As the generation of extreme adaptive optics (XAO) instruments is coming online, more advanced wavefront control schemes developed in the context of space-borne coronagraphy like speckle nulling (Bordé & Traub 2006) or the general framework of electric field conjugation (Give'On 2009) are being ported on-sky (Martinache et al 2014;Cady et al 2013). Nevertheless, it remains remarkable that such a venerable approach (the original masking idea by Fizeau was actually first tested in the 1870s), has remained relevant for well over a century.…”

Section: Introductionmentioning

confidence: 99%

Closed-loop focal plane wavefront control with the SCExAO instrument

Martinache

Jovanović

Guyon

2016

A&A

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Aims. This article describes the implementation of a focal plane based wavefront control loop on the high-contrast imaging instrument SCExAO (Subaru Coronagraphic Extreme Adaptive Optics). The sensor relies on the Fourier analysis of conventional focal-plane images acquired after an asymmetric mask is introduced in the pupil of the instrument. Methods. This absolute sensor is used here in a closed-loop to compensate for the non-common path errors that normally affects any imaging system relying on an upstream adaptive optics system.This specific implementation was used to control low-order modes corresponding to eight zernike modes (from focus to spherical). Results. This loop was successfully run on-sky at the Subaru Telescope and is used to offset the SCExAO deformable mirror shape used as a zero-point by the high-order wavefront sensor. The paper details the range of errors this wavefront-sensing approach can operate within and explores the impact of saturation of the data and how it can be bypassed, at a cost in performance. Conclusions. Beyond this application, because of its low hardware impact, the asymmetric pupil Fourier wavefront sensor (APF-WFS) can easily be ported in a wide variety of wavefront sensing contexts, for ground-as well space-borne telescopes, and for telescope pupils that can be continuous, segmented or even sparse. The technique is powerful because it measures the wavefront where it really matters, at the level of the science detector.

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Section: Introductionmentioning

confidence: 99%

Closed-loop focal plane wavefront control with the SCExAO instrument

Martinache

Jovanović

Guyon

2016

A&A

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“…The resulting expression eliminates the need to consider aberrations upstream of the beam splitter, which separates the optical paths of the SC and WFS, and the result is a versions of Eqs. (39) and (40) with many fewer unknown functions.…”

Section: Explicit Determination Of Unknown Aberrationsmentioning

confidence: 99%

“…(39), plus terms that are nonlinear in the {Ã k }, if desired. Here, this is called the "black box model" since the unknown aberrations are only taken into account via the resulting image-plane field u u .…”

Section: Black Box Modelsmentioning

confidence: 99%

“…Once the amplitude and phase of u u (ρ) have been determined, the DM is commanded to implement a canceling sinusoidal aberration δm that gives rise to a field u c (ρ) that is equal in amplitude, but opposite in phase to, u u (ρ). In reality neither u u nor u c will be independent of the atmospheric modulation, but some cancellation can be achieved, and [39] demonstrates considerable success on-sky with this technique.…”

Section: Black Box Modelsmentioning

confidence: 99%

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Statistical framework for the utilization of simultaneous pupil plane and focal plane telemetry for exoplanet imaging I Accounting for aberrations in multiple planes

Frazin

2016

J. Opt. Soc. Am. A

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A new generation of telescopes with mirror diameters of 20 m or more, called extremely large telescopes (ELTs) has the potential to provide unprecedented imaging and spectroscopy of exo-planetary systems, if the difficulties in achieving the extremely high dynamic range required to differentiate the planetary signal from the star can be overcome to a sufficient degree. Fully utilizing the potential of ELTs for exoplanet imaging will likely require simultaneous and self-consistent determination of both the planetary image and the unknown aberrations in multiple planes of the optical system, using statistical inference based on the wavefront sensor and science camera data streams. This approach promises to overcome the most important systematic errors inherent in the various schemes based on differential imaging, such as ADI and SDI. This paper is the first in a series on this subject, in which a formalism is established for the exoplanet imaging problem, setting the stage for the statistical inference methods to follow in the future. Every effort has been made to be rigorous and complete, so that validity of approximations to be made later can be assessed. Here, the polarimetric image is expressed in terms of aberrations in the various planes of a polarizing telescope with an adaptive optics system. Further, it is shown that current methods that utilize focal plane sensing to correct the speckle field, e.g., electric field conjugation, rely on the tacit assumption that aberrations on multiple optical surfaces can be represented as aberration on a single optical surface, ultimately limiting their potential effectiveness for ground-based astronomy.

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“…HiCIAO received its beam from AO188, 10 a 188-actuator adaptive optics system. AO188 is currently being augmented by SCExAO, which uses a pyramid wavefront sensor, active speckle nulling, 11 and a choice of several coronagraphs to dramatically improve contrast. Figure 2 shows a schematic of the Nasmyth bench as it will function with CHARIS.…”

Section: Charis Specificationsmentioning

confidence: 99%

CHARIS science: performance simulations for the Subaru Telescope's third-generation of exoplanet imaging instrumentation

Brandt¹,

McElwain

Janson

et al. 2014

SPIE Proceedings

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We describe the expected scientific capabilities of CHARIS, a high-contrast integral-field spectrograph (IFS) currently under construction for the Subaru telescope. CHARIS is part of a new generation of instruments, enabled by extreme adaptive optics (AO) systems (including SCExAO at Subaru), that promise greatly improved contrasts at small angular separation thanks to their ability to use spectral information to distinguish planets from quasistatic speckles in the stellar point-spread function (PSF). CHARIS is similar in concept to GPI and SPHERE, on Gemini South and the Very Large Telescope, respectively, but will be unique in its ability to simultaneously cover the entire near-infrared J, H, and K bands with a low-resolution mode. This extraordinarily broad wavelength coverage will enable spectral differential imaging down to angular separations of a few λ/D, corresponding to ∼0. 1. SCExAO will also offer contrast approaching 10 −5 at similar separations, ∼0. 1-0. 2. The discovery yield of a CHARIS survey will depend on the exoplanet distribution function at around 10 AU. If the distribution of planets discovered by radial velocity surveys extends unchanged to ∼20 AU, observations of ∼200 mostly young, nearby stars targeted by existing high-contrast instruments might find ∼1-3 planets. Carefully optimizing the target sample could improve this yield by a factor of a few, while an upturn in frequency at a few AU could also increase the number of detections. CHARIS, with a higher spectral resolution mode of R ∼ 75, will also be among the best instruments to characterize planets and brown dwarfs like HR 8799 cde and κ And b. We then use the thousands of mini spectra to reconstruct the data cube, the spectrum of each spatial element of the field-of-view.

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On-Sky Speckle Nulling Demonstration at Small Angular Separation with SCExAO

Cited by 85 publications

References 26 publications

Closed-loop focal plane wavefront control with the SCExAO instrument

Closed-loop focal plane wavefront control with the SCExAO instrument

Statistical framework for the utilization of simultaneous pupil plane and focal plane telemetry for exoplanet imaging I Accounting for aberrations in multiple planes

CHARIS science: performance simulations for the Subaru Telescope's third-generation of exoplanet imaging instrumentation

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