Mistral: a myopic edge-preserving image restoration method, with application to astronomical adaptive-optics-corrected long-exposure images

Mugnier, Laurent M.; Fusco, Thierry; Conan, Jean-Marc

doi:10.1364/josaa.21.001841

Cited by 150 publications

(155 citation statements)

References 36 publications

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“…The projected ellipse parameters can also be extracted from images deconvolved with an alternate algorithm such as Mistral (Conan et al 2000;Mugnier et al 2004). These contours provide a direct measurement of details of the projected shape of the asteroid, allowing the construction of the radius vector model that we present in Carry et al (2010b), providing a more refined description of the shape of Lutetia.…”

Section: Discussionmentioning

confidence: 99%

Physical properties of the ESA Rosetta target asteroid (21) Lutetia

Drummond¹,

Conrad

Merline

et al. 2010

A&A

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Context. Asteroid (21) Lutetia was the target of the ESA Rosetta mission flyby in 2010 July. Aims. We seek the best size estimates of the asteroid, the direction of its spin axis, and its bulk density, assuming its shape is well described by a smooth featureless triaxial ellipsoid. We also aim to evaluate the deviations from this assumption. Methods. We derive these quantities from the outlines of the asteroid in 307 images of its resolved apparent disk obtained with adaptive optics (AO) at Keck II and VLT, and combine these with recent mass determinations to estimate a bulk density. Results. Our best triaxial ellipsoid diameters for Lutetia, based on our AO images alone, are a × b × c = 132 × 101 × 93 km, with uncertainties of 4 × 3 × 13 km including estimated systematics, with a rotational pole within 5The AO model fit itself has internal precisions of 1 × 1 × 8 km, but it is evident both from this model derived from limited viewing aspects and the radius vector model given in a companion paper, that Lutetia significantly departs from an idealized ellipsoid. In particular, the long axis may be overestimated from the AO images alone by about 10 km. Therefore, we combine the best aspects of the radius vector and ellipsoid model into a hybrid ellipsoid model, as our final result, of diameters 124 ± 5 × 101 ± 4 × 93 ± 13 km that can be used to estimate volumes, sizes, and projected areas. The adopted pole position is withinConclusions. Using two separately determined masses and the volume of our hybrid model, we estimate a density of 3.5 ± 1.1 or 4.3 ± 0.8 g cm −3 . From the density evidence alone, we argue that this favors an enstatite-chondrite composition, although other compositions are formally allowed at the extremes (low-porosity CV/CO carbonaceous chondrite or high-porosity metallic). We discuss this in the context of other evidence.

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Section: Discussionmentioning

confidence: 99%

Physical properties of the ESA Rosetta target asteroid (21) Lutetia

Drummond¹,

Conrad

Merline

et al. 2010

A&A

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“…We then restored the images to optimal angular-resolution using the Mistral deconvolution algorithm (Conan et al 2000;Mugnier et al 2004). The validity of this approach (real-time Adaptive-Optics correction followed by a posteriori deconvolution) has already been demonstrated elsewhere (Marchis et al 2002;Witasse et al 2006).…”

Section: Disk-resolved Imaging Observationsmentioning

confidence: 99%

Physical properties of the ESA Rosetta target asteroid (21) Lutetia

Carry

Kaasalainen

Leyrat

et al. 2010

A&A

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Aims. We determine the physical properties (spin state and shape) of asteroid (21) Lutetia, target of the International Rosetta Mission of the European Space Agency, to help in preparing for observations during the flyby on 2010 July 10 by predicting the orientation of Lutetia as seen from Rosetta. Methods. We use our novel KOALA inversion algorithm to determine the physical properties of asteroids from a combination of optical lightcurves, disk-resolved images, and stellar occultations, although the last are not available for (21) Lutetia. Results. We find the spin axis of (21) Lutetia to lie within 5 • of (λ = 52 • , β = −6 • ) in the Ecliptic J2000 reference frame (equatorial α = 52 • , δ = +12 • ), and determine an improved sidereal period of 8.168 270±0.000 001 h. This pole solution implies that the southern hemisphere of Lutetia will be in "seasonal" shadow at the time of the flyby. The apparent cross-section of Lutetia is triangular when seen "pole-on" and more rectangular "equator-on". The best-fit model suggests there are several concavities. The largest of these is close to the north pole and may be associated with strong impacts.

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“…Because calibration is assumed to be performed with high flux levels, we adopt a non-stationary white Gaussian model, which is a good approximation of a mix of photon and detector noises. Its variance is the sum of the photon and detector noise variances: (Mugnier et al 2004), with t the pixel position in the detector plane. The former can be estimated as the image itself thresholded to positive values, and the latter can be calibrated prior to the observations.…”

Section: Coffee: Principlementioning

confidence: 99%

Coronagraphic phase diversity: performance study and laboratory demonstration

Paul

Sauvage

Mugnier

2013

A&A

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Context. The final performance of current and future instruments dedicated to exoplanet detection and characterization (such as SPHERE on the European Very Large Telescope, GPI on Gemini North, or future instruments on Extremely Large Telescopes) is limited by uncorrected quasi-static aberrations. These aberrations create long-lived speckles in the scientific image plane, which can easily be mistaken for planets. Aims. Common adaptive optics systems require dedicated components to perform wave-front analysis. The ultimate wave-front measurement performance is thus limited by the unavoidable differential aberrations between the wave-front sensor and the scientific camera. To reach the level of detectivity required by high-contrast imaging, these differential aberrations must be estimated and compensated for. In this paper, we characterize and experimentally validate a wave-front sensing method that relies on focal-plane data. Methods. Our method, called COFFEE (for COronagraphic Focal-plane wave-Front Estimation for Exoplanet detection), is based on a Bayesian approach, and it consists in an extension of phase diversity to high-contrast imaging. It estimates the differential aberrations using only two focal-plane coronagraphic images recorded from the scientific camera itself. Results. We first present a thorough characterization of COFFEE's performance by means of numerical simulations. This characterization is then compared with an experimental validation of COFFEE using an in-house adaptive optics bench and an apodized Roddier & Roddier phase mask coronagraph. An excellent match between experimental results and the theoretical study is found. Lastly, we present a preliminary validation of COFFEE's ability to compensate for the aberrations upstream of a coronagraph.

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Mistral: a myopic edge-preserving image restoration method, with application to astronomical adaptive-optics-corrected long-exposure images

Cited by 150 publications

References 36 publications

Physical properties of the ESA Rosetta target asteroid (21) Lutetia

Physical properties of the ESA Rosetta target asteroid (21) Lutetia

Physical properties of the ESA Rosetta target asteroid (21) Lutetia

Coronagraphic phase diversity: performance study and laboratory demonstration

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