Infrared differential imager and spectrograph for SPHERE: performance status with extreme adaptive optics before shipment to ESO/VLT

Langlois, M.; Vigan, A.; Moutou, C.; Dohlen, Kjetil; Costille, A.; Mignant, D. Le; Martínez, P.; Mouillet, D.; Boccaletti, A.; Moeller-Nilsson, O.; Sauvage, J.-F.; Mugnier, Laurent M.; Feldt, M.; Gry, C.; Wildi, F.; Beuzit, Jean-Luc

doi:10.1117/12.927099

Cited by 7 publications

(6 citation statements)

References 15 publications

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“…High-precision relative astrometry and efficient attenuation of the stellar residuals by image post-processing techniques critically depend of a precise estimate of the location of the star behind a coronagraphic mask 22,23 . For this purpose, a calibration image is recorded before and after a science sequence with four crosswise faint stellar replicas produced by applying a periodic modulation on the SPHERE deformable mirror 24 . The specifications for the SPHERE astrometric accuracy are 5 mas (goal 1 mas).…”

Section: Introductionmentioning

confidence: 99%

SPHERE IRDIS and IFS astrometric strategy and calibration

et al. 2016

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We present the current results of the astrometric characterization of the VLT planet finder SPHERE over 2 years of on-sky operations. We first describe the criteria for the selection of the astrometric fields used for calibrating the science data: binaries, multiple systems, and stellar clusters. The analysis includes measurements of the pixel scale and the position angle with respect to the North for both near-infrared subsystems, the camera IRDIS and the integral field spectrometer IFS, as well as the distortion for the IRDIS camera. The IRDIS distortion is shown to be dominated by an anamorphism of 0.60±0.02% between the horizontal and vertical directions of the detector, i.e. 6 mas at 1 arcsec. The anamorphism is produced by the cylindrical mirrors in the common path structure hence common to all three SPHERE science subsystems (IRDIS, IFS, and ZIMPOL), except for the relative orientation of their field of view. The current estimates of the pixel scale and North angle for IRDIS are 12.255±0.009 milliarcseconds/pixel for H2 coronagraphic images and -1.75±0.08• . Analyses of the IFS data indicate a pixel scale of 7.46±0.02 milliarcseconds/pixel and a North angle of -102.18±0.13• . We finally discuss plans for providing astrometric calibration to the SPHERE users outside the instrument consortium.

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Section: Introductionmentioning

confidence: 99%

SPHERE IRDIS and IFS astrometric strategy and calibration

et al. 2016

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“…The calibration spots are produced by applying a periodic modulation on the AO deformable mirror. 37 To maximize the S/N of the detected point sources and measure precise position angles, a precise azimuthal realignment of the individual images before their combination is mandatory.…”

Section: Exoplanet Imaging With Vlt/sphere and Astrometric Requirementsmentioning

confidence: 99%

Lessons learned from SPHERE for the astrometric strategy of the next generation of exoplanet imaging instruments

Maire

Langlois

Delorme

et al. 2021

J. Astron. Telesc. Instrum. Syst.

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Measuring the orbits of directly imaged exoplanets requires precise astrometry at the milliarcsec level over long periods of time due to their wide separation to the stars (≳10 au) and long orbital period (≳20 yr). To reach this challenging goal, a specific strategy was implemented for the instrument Spectro-Polarimetric High-contrast Exoplanet Research (SPHERE), the first dedicated exoplanet imaging instrument at the Very Large Telescope of the European Southern Observatory (ESO). A key part of this strategy relies on the astrometric stability of the instrument over time. We monitored for five years the evolution of the optical distortion, pixel scale, and orientation to the True North of SPHERE images using the near-infrared instrument IRDIS. We show that the instrument calibration achieves a positional stability of ∼1 mas over 2″ field of views. We also discuss the SPHERE astrometric strategy, issues encountered in the course of the on-sky operations, and lessons learned for the next generation of exoplanet imaging instruments on the Extremely Large Telescope being built by ESO. © The Authors. Published by SPIE under a Creative Commons Attribution 4.0 Unported License. Distribution or reproduction of this work in whole or in part requires full attribution of the original publication, including its DOI.

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“…The calibration spots are produced by applying a periodic modulation on the AO deformable mirror. 35 To maximize the S/N of the detected point sources and measure precise position angles, a precise azimuthal realignment of the individual images before their combination is mandatory.…”

Section: Exoplanet Imaging With Vlt/sphere and Astrometric Requirementsmentioning

confidence: 99%

Lessons learned from SPHERE for the astrometric strategy of the next generation of exoplanet imaging instruments

Maire¹,

Langlois²,

Delorme³

et al. 2021

Preprint

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Measuring the orbits of directly-imaged exoplanets requires precise astrometry at the milliarcsec level over long periods of time due to their wide separation to the stars ( 10 au) and long orbital period ( 20 yr). To reach this challenging goal, a specific strategy was implemented for the instrument Spectro-Polarimetric High-contrast Exoplanet REsearch (SPHERE), the first dedicated exoplanet imaging instrument at the Very Large Telescope of the European Southern Observatory (ESO). A key part of this strategy relies on the astrometric stability of the instrument over time. We monitored for five years the evolution of the optical distortion, pixel scale, and orientation to the True North of SPHERE images using the near-infrared instrument IRDIS. We show that the instrument calibration achieves a positional stability of ∼1 mas over 2 field of views. We also discuss the SPHERE astrometric strategy, issues encountered in the course of the on-sky operations, and lessons learned for the next generation of exoplanet imaging instruments on the Extremely Large Telescope being built by ESO.

show abstract

Infrared differential imager and spectrograph for SPHERE: performance status with extreme adaptive optics before shipment to ESO/VLT

Cited by 7 publications

References 15 publications

SPHERE IRDIS and IFS astrometric strategy and calibration

SPHERE IRDIS and IFS astrometric strategy and calibration

Lessons learned from SPHERE for the astrometric strategy of the next generation of exoplanet imaging instruments

Lessons learned from SPHERE for the astrometric strategy of the next generation of exoplanet imaging instruments

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