A deformable secondary mirror for the VLT

Arsenault, Robin; Biasi, Roberto; Gallieni, Daniele; Riccardi, Armando; Lazzarini, Paolo; Hubin, N.; Fedrigo, Enrico; Donaldson, Rob; Oberti, Sylvain; Stroebele, Stefan; Conzelmann, Ralf; Duchateau, M.

doi:10.1117/12.672879

Cited by 33 publications

(24 citation statements)

References 5 publications

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“…HAWK-I is also designed to work in future with a groundlayer adaptive optics module (GRAAL) as part of the Adaptive Optics Facility (Arsenault et al 2006) for the VLT. The facility is expected at the telescope around 2012, at which point the GRAAL module will be brought into operation.…”

Section: General Overviewmentioning

confidence: 99%

“…The laser beams as well as the natural guide star beams will be picked-off in the ground-layer adaptive optics module (GRAAL, Arsenault et al 2006) located between HAWK-I and the telescope adapter-rotator flange. The laser guide star wavefront sensors will have to compensate for the focus variations due to the finite altitude of the laser spots and the telescope position.…”

Section: Outlook -Ground-layer Adaptive Opticsmentioning

confidence: 99%

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HAWK-I: the high-acuity wide-field K-band imager for the ESO Very Large Telescope

Kissler-Patig¹,

Pirard²,

Casali³

et al. 2008

A&A

144

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We describe the design, development, and performance of HAWK-I, the new High-Acuity Wide-field K-band Imager for ESO's Very Large Telescope, which is equipped with a mosaic of four 2 k × 2 k arrays and operates from 0.9−2.4 μm over 7.5 × 7.5 with 0.1 pixels. A novel feature is the use of all reflective optics that, together with filters of excellent throughput and detectors of high quantum efficiency, has yielded an extremely high throughput. Commissioning and science verification observations have already delivered a variety of excellent and deep images that demonstrate its high scientific potential for addressing important astrophysical questions of current interest.

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Section: General Overviewmentioning

confidence: 99%

Section: Outlook -Ground-layer Adaptive Opticsmentioning

confidence: 99%

HAWK-I: the high-acuity wide-field K-band imager for the ESO Very Large Telescope

Kissler-Patig¹,

Pirard²,

Casali³

et al. 2008

A&A

144

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“…The detectors and the filter wheel unit are connected to the second stage of the Closed Cycle Cooler and operated at a temperature close to 75−80 K. The remaining parts of the instrument are cooled to a temperature below 140 K. The acquisition system is based on the Infrared Array Control Electronics system (IRACE) developed at ESO. HAWK-I also is designed to work with a groundlayer adaptive optics module (GRAAL) as part of the Adaptive Optics Facility (Arsenault et al 2006) for the VLT (scheduled to be installed in the second half of 2014). HAWK-I broad band filters follow the Mauna Kea Observatory specification.…”

Section: Hawk-i@vltmentioning

confidence: 99%

Ground-based astrometry with wide field imagers

Libralato

Bellini

Bedin

et al. 2014

A&A

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High-precision astrometry requires accurate point-spread function modeling and accurate geometric-distortion corrections. This paper demonstrates that it is possible to achieve both requirements with data collected at the high acuity wide-field K-band imager (HAWK-I), a wide-field imager installed at the Nasmyth focus of UT4/VLT ESO 8 m telescope. Our final astrometric precision reaches ∼3 mas per coordinate for a well-exposed star in a single image with a systematic error less than 0.1 mas. We constructed calibrated astro-photometric catalogs and atlases of seven fields: the Baade's window, NGC 6656, NGC 6121, NGC 6822, NGC 6388, NGC 104, and the James Webb Space Telescope calibration field (in the Large Magellanic Cloud). We make these catalogs and images electronically available to the community. Furthermore, as a demonstration of the efficacy of our approach, we combined archival material taken with the optical wide-field imager at the MPI/ESO 2.2 m with HAWK-I observations. We showed that we are able to achieve an excellent separation between cluster members and field objects for NGC 6656 and NGC 6121 with a time base-line of about 8 years. Using both HST and HAWK-I data, we also study the radial distribution of the SGB populations in NGC 6656 and conclude that the radial trend is flat within our uncertainty. We also provide membership probabilities for most of the stars in NGC 6656 and NGC 6121 catalogs and estimate membership for the published variable stars in these two fields.

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“…Hopkins (AZ) successfully started the operation on sky of the first adaptive secondary mirror build with voice coil motor technology [1]. After this 640mm diameter mirror, four more units are currently being built, namely two adaptive secondary for the Large Binocular Telescope (LBT) [2], one for the Magellan telescope and one for the VLT-UT4 in the frame of the Adaptive Optics Facility (AOF) programme [3]. All these units shares the same technology which is based on a free-floating Zerodur thin mirror, typically from 1.6mm to 2mm thick, having a pattern of permanent magnets glued on its back surface.…”

Section: Introductionmentioning

confidence: 99%

Voice-coil technology for the E-ELT M4 Adaptive Unit

Gallieni¹,

Tintori²,

Mantegazza³

et al. 2010

1st AO4ELT Conference - Adaptive Optics for Extremely Large Telescopes

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Abstract. We present our design of the E-ELT M4 Adaptive Unit based on voice-coil driven deformable mirror technology. This technology was developed by INAF-Arcetri, Microgate and ADS team in the past 15 years and it has been adopted by a number of large ground based telescopes as the MMT, LBT, Magellan and lastly the VLT in the frame of the Adaptive Telescope Facility project. Our design is based on contactless force actuators made by permanent magnets glued on the back of the deformable mirror and coils mounted on a stiff reference structure. We use capacitive sensors to close a position loop co-located with each actuator. Dedicated high performance parallel processors are used to implement the local de-centralized control at actuator level and a centralized feed-forward computation of all the actuators forces. This allowed achieving in our previous systems dynamic performances well in line with the requirements of the M4 Adaptive Unit (M4AU) case. The actuator density of our design is in the order of 30-mm spacing for a figure of about 6000 actuators on the M4AU and it allows fulfilling the fitting error and corrections requirements of the E-ELT high order DM. Moreover, our contact-less technology makes the Deformable Mirror tolerant to up 5% actuators failures without spoiling system capability to reach its specified performances, besides allowing large mechanical tolerances between the reference structure and the deformable mirror. Finally, we present the Demonstration Prototype we are building in the frame of the M4AU Phase B study to measure the optical dynamical performances predicted by our design. Such a prototype will be fully representative of the M4AU features, in particular it will address the controllability of two adjacent segments of the 2-mm thick mirror and implement the actuators "brick" modular concept that has been adopted to dramatically improve the maintainability of the final unit.

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A deformable secondary mirror for the VLT

Cited by 33 publications

References 5 publications

HAWK-I: the high-acuity wide-field K-band imager for the ESO Very Large Telescope

HAWK-I: the high-acuity wide-field K-band imager for the ESO Very Large Telescope

Ground-based astrometry with wide field imagers

Voice-coil technology for the E-ELT M4 Adaptive Unit

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