VISIR upgrade overview and status

Kerber, F.; Käufl, H. U.; Baksai, Pedro; Lieto, Nicola Di; Dobrzycka, D.; Duhoux, Philippe; Finger, Gert; Heikamp, S.; Ives, Derek; Jakob, Gerd; Lundin, Lars; Mawet, Dimitri; Mehrgan, Leander; Momany, Y.; Moreau, Vincent; Pantin, É.; Riquelme, M.; Sandrock, Stefan; Siebenmorgen, R.; Smette, A.; Taylor, J.; Ancker, M. E. van den; Valdes, G.; Venema, Lars; Weilenmann, U.

doi:10.1117/12.2055172

Cited by 11 publications

(9 citation statements)

References 11 publications

(12 reference statements)

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“…When the commissioning of VISIR showed a lack of sensitivity, we therefore decided, as a first step, to invest dedicated effort in evaluating the detector quantum efficiency. The quantum efficiency of the AQUARIUS detector was found to be 40 ± 1.5%, a value which is within expectations 4,5 . Thus, an intrinsically low QE was not causing the observed under-performance.…”

Section: Commissioning and Performance Problemssupporting

confidence: 70%

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VISIR upgrade overview: all's well that ends well

Kerber¹,

Käufl²,

Tristram³

et al. 2016

SPIE Proceedings

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We present an overview of the VISIR instrument after its upgrade and return to science operations. VISIR is the midinfrared imager and spectrograph at ESO's VLT. The project team is comprised of ESO staff and members of the original VISIR consortium: CEA Saclay and ASTRON. The project plan was based on input from the ESO user community with the goal of enhancing the scientific performance and efficiency of VISIR by a combination of measures: installation of improved hardware, optimization of instrument operations and software support. The cornerstone of the upgrade is the 1k by 1k Si:As AQUARIUS detector array manufactured by Raytheon. In addition, a new prism spectroscopic mode covers the whole N-band in a single observation. Finally, new scientific capabilities for high resolution and high-contrast imaging are offered by sub-aperture mask and coronagraphic modes. In order to make optimal use of favourable atmospheric conditions, a water vapour monitor has been deployed on Paranal, allowing for real-time decisions and the introduction of a user-defined constraint on water vapour. During the commissioning in 2012, it was found that the on-sky sensitivity of the AQUARIUS detector was significantly below expectations. Extensive testing of the detector arrays in the laboratory and on-sky enabled us to diagnose the cause for the shortcoming of the detector as excess low frequency noise. It is inherent to the design chosen for this detector and cannot be remedied by changing the detector set-up. Since this is a form of correlated noise, its impact can be limited by modulating the scene recorded by the detector. After careful analysis, we have implemented fast (up to 4 Hz) chopping with field stabilization using the secondary mirror of the VLT. During commissioning, the upgraded VISIR has been confirmed to be more sensitive than the old instrument, and in particular for low-resolution spectroscopy in the N-band, a gain of a factor 6 is realized in observing efficiency. After overcoming several additional technical problems, VISIR is back in Science Operations since April 2015. In addition an upgrade of the IT infrastructure related to VISIR has been conducted in order to support burst-mode operations. Science Verification of the new modes was performed in Feb 2016. The upgraded VISIR is a powerful instrument providing close to background limited performance for diffraction-limited observations at an 8-m telescope. It offers synergies with facilities such as ALMA, JWST, VLTI and SOFIA, while a wealth of targets is available from survey works like WISE. In addition, it will bring confirmation of the technical readiness and scientific value of several aspects for future mid-IR instrumentation at Extremely Large Telescopes. We also present several lessons learned during the project.

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Section: Commissioning and Performance Problemssupporting

confidence: 70%

“…The upgrade of VISIR has been described at previous SPIE conferences 2,3,4 . For convenience some of the relevant information is repeated and then an update on the recent developments will be given.…”

Section: Introductionmentioning

confidence: 99%

VISIR upgrade overview: all's well that ends well

Kerber¹,

Käufl²,

Tristram³

et al. 2016

SPIE Proceedings

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“…While the first on-sky results obtained with the AGPM in May 2012 were promising, VISIR was removed from the telescope due to detector issues. 12 Over the last two years, VISIR has been recommissioned, 13 and science verification observations have recently been performed. 14 These data are currently being processed to assess the on-sky performance of the AGPM.…”

Section: Commissioning and On-sky Operationsmentioning

confidence: 99%

Three years of harvest with the vector vortex coronagraph in the thermal infrared

et al. 2016

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For several years, we have been developing vortex phase masks based on sub-wavelength gratings, known as Annular Groove Phase Masks. Etched onto diamond substrates, these AGPMs are currently designed to be used in the thermal infrared (ranging from 3 to 13 µm). Our AGPMs were first installed on VLT/NACO and VLT/VISIR in 2012, followed by LBT/LMIRCam in 2013 and Keck/NIRC2 in 2015. In this paper, we review the development, commissioning, on-sky performance, and early scientific results of these new coronagraphic modes and report on the lessons learned. We conclude with perspectives for future developments and applications.

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“…This kind of coronagraph is attractive for several reasons, including high extinction ratio, achromatic properties, a continuous discovery space and small IWA. For all these reasons, this kind of coronagraph can be found in several leading instruments: the Palomar infrared camera PHARO, 2 Subaru/SCExAO, 3 VLT/VISIR, 4,5 VLT/NACO, 6 LBT/LMIRCam 7 and recently Keck/NIRC2 (first light obtained in June 2015, see Ref. 8 in these proceedings and Serabyn et al in prep).…”

Section: Introductionmentioning

confidence: 98%

The QACITS pointing sensor: from theory to on-sky operation on Keck/NIRC2

Huby

Absil

Mawet

et al. 2016

Adaptive Optics Systems V

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Small inner working angle coronagraphs are essential to benefit from the full potential of large and future extremely large ground-based telescopes, especially in the context of the detection and characterization of exoplanets. Among existing solutions, the vortex coronagraph stands as one of the most effective and promising solutions. However, for focal-plane coronagraph, a small inner working angle comes necessarily at the cost of a high sensitivity to pointing errors. This is the reason why a pointing control system is imperative to stabilize the star on the vortex center against pointing drifts due to mechanical flexures, that generally occur during observation due for instance to temperature and/or gravity variations. We have therefore developed a technique called QACITS 1 (Quadrant Analysis of Coronagraphic Images for Tip-tilt Sensing), which is based on the analysis of the coronagraphic image shape to infer the amount of pointing error. It has been shown that the flux gradient in the image is directly related to the amount of tip-tilt affecting the beam. The main advantage of this technique is that it does not require any additional setup and can thus be easily implemented on all current facilities equipped with a vortex phase mask. In this paper, we focus on the implementation of the QACITS sensor at Keck/NIRC2, where an L-band AGPM has been recently commissioned (June and October 2015), successfully validating the QACITS estimator in the case of a centrally obstructed pupil. The algorithm has been designed to be easily handled by any user observing in vortex mode, which is available for science in shared risk mode since 2016B.

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VISIR upgrade overview and status

Cited by 11 publications

References 11 publications

VISIR upgrade overview: all's well that ends well

VISIR upgrade overview: all's well that ends well

Three years of harvest with the vector vortex coronagraph in the thermal infrared

The QACITS pointing sensor: from theory to on-sky operation on Keck/NIRC2

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