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Proceedings Paper

The KMOS Integral Field System: fabrication, alignment, and test of 1000+ optical surfaces
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Paper Abstract

The Centre for Advanced Instrumentation (CfAI) of Durham University (UK) has recently successfully completed the development of 24 Integral Field Units (IFUs) for the K-band Multi-Object Spectrometer (KMOS). KMOS is a second generation instrument for ESO’s Very Large Telescope (VLT) which is due for delivery during the summer of 2012. The KMOS IFU is based on the Advanced Image Slicer Concept developed by the CfAI and previously successfully implemented on the Gemini Near-InfraRed Spectrograph and JWST NIRSpec. Each IFU contains 14 channels which have to be accurately aligned. In addition, all 24 IFUs have to be co-aligned requiring the accurate alignment of an unprecedented grand total of 1152 optical surfaces. In this paper we describe how this has been achieved through the use of complex monolithic multi-faceted metal mirror arrays, which were fabricated in-house by means of freeform diamond machining. We will summarise the results from the metrology performed on each of the optical components and describe how these were integrated and aligned into the system. We will also summarise the results from the system level acceptance tests, which demonstrate the excellent performance of the IFUs. Each of the 24 IFUs is essentially diffraction limited across the entire field (Strehl ratios ~ 0.8) with throughput predictions (based on measurements of the surface roughness) rising from 86% at a wavelength of 1 micron to 93% at 2.5 micron. We believe that this level of performance has not previously been achieved in any image slicing IFU and showcases the potential of the current state-of-the-art technology.

Paper Details

Date Published: 13 September 2012
PDF: 13 pages
Proc. SPIE 8450, Modern Technologies in Space- and Ground-based Telescopes and Instrumentation II, 84501M (13 September 2012); doi: 10.1117/12.925134
Show Author Affiliations
Cornelis M. Dubbeldam, Durham Univ. (United Kingdom)
Paul Clark, Durham Univ. (United Kingdom)
Robert Content, Durham Univ. (United Kingdom)
Andrew K. Kirby, Durham Univ. (United Kingdom)
Ken Parkin, Durham Univ. (United Kingdom)
David J. Robertson, Durham Univ. (United Kingdom)
Stephen Rolt, Durham Univ. (United Kingdom)
David A. Ryder, Durham Univ. (United Kingdom)
Ray M. Sharples, Durham Univ. (United Kingdom)

Published in SPIE Proceedings Vol. 8450:
Modern Technologies in Space- and Ground-based Telescopes and Instrumentation II
Ramón Navarro; Colin R. Cunningham; Eric Prieto, Editor(s)

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