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The pre-optics mechanism prototypes for HARMONI
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Paper Abstract

HARMONI is a visible and near-infrared (0.47 to 2.45 μm) integral field spectrograph, providing the ELT's core spectroscopic capability at first light. A pre-optics subsystem provides four selectable spatial pixel scales, in addition to other beam conditioning functions such as shutter and pupil masks. For the validation of the mechanisms in charge of these functions (fast shutter and the plane mask wheel) we have planned some prototypes to test the design solutions.

The focal plane mask wheel sits in the input focus of the cryostat. It provides 16 user-selectable positions for masks (28x40 mm) used in observation. The key driver for this mechanism is the high repeatability (±2.5 μm) required, equivalent to ~1mas in the input focal plane. The IAC has previously designed, manufactured, tested and put in operation cryogenic wheels with high repeatability; however, the challenge of obtaining a wheel with such repeatability requires testing new concepts of detent positioning systems.

The shutter allows for exposures shorter than the minimum read time of the near-IR detectors and is needed for any CCD observations with the visible cameras. A dual shutter design is needed to achieve the necessary open/close times (<20 ms), but this also provides some redundancy and a graceful failure mode for this critical device. To mitigate risks on the proper behaviour of a fast cryogenics shutter a prototype based on a simple concept has been manufactured. We present the design and results for the performed cryogenic tests of a mask wheel and a shutter prototypes that we have developed.

Paper Details

Date Published: 10 July 2018
PDF: 9 pages
Proc. SPIE 10706, Advances in Optical and Mechanical Technologies for Telescopes and Instrumentation III, 107063N (10 July 2018); doi: 10.1117/12.2313312
Show Author Affiliations
Elvio Hernández, Instituto de Astrofísica de Canarias (Spain)
Jose V. Gigante, Instituto de Astrofísica de Canarias (Spain)
Luis F. Rodríguez, Instituto de Astrofísica de Canarias (Spain)
Univ. de La Laguna (Spain)
José M. Herreros, Instituto de Astrofísica de Canarias (Spain)
Begoña García-Lorenzo, Instituto de Astrofísica de Canarias (Spain)
Univ. de La Laguna (Spain)
Evencio Mediavilla, Instituto de Astrofísica de Canarias (Spain)
Univ. de La Laguna (Spain)
Niranjan Thatte, Univ. of Oxford (United Kingdom)
Ian Bryson, UK Astronomy Technology Ctr. (United Kingdom)
Hermine Schnetler, UK Astronomy Technology Ctr. (United Kingdom)
Fraser Clarke, Univ. of Oxford (United Kingdom)
Matthias Tecza, Univ. of Oxford (United Kingdom)


Published in SPIE Proceedings Vol. 10706:
Advances in Optical and Mechanical Technologies for Telescopes and Instrumentation III
Ramón Navarro; Roland Geyl, Editor(s)

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