19 July 2010 Flight model performance of the integral field unit for the James Webb Space Telescope's near-infrared spectrograph
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Abstract
The Near Infrared Spectrograph (NIRSpec) developed by EADS Astrium GmbH for the European Space Agency (ESA) is a spectrograph covering the 0.6-5.0 μm waveband to fly on the James Webb Space Telescope (JWST). NIRSpec will be primarily operated as a multi-object spectrograph but also includes an integral field unit (IFU) allowing a 3×3 arcsec field of view to be sampled continuously with 0.1 arcsec spatial resolution. The IFU, based on an advanced image slicer concept, is a very compact athermal unit made of aluminium. It contains three 30-element monolithic mirror arrays forming slicer, pupil and slit mirrors, and single-surface image relay and plane fold mirrors, produced using 5-axis diamond-machining techniques. Many of the mirrors have complex surfaces like toric sections with 3rd-order corrections in order to achieve the required performance within a small allowed volume, and could only have been fabricated with the most advanced free-form machining. The mechanical design accommodates the differential expansion between the aluminium IFU and its titanium parent assembly across a 250K drop to operating temperature using an isostatic mounting system. This paper presents the development of the IFU from the design and diamond-machining techniques to the optical and cryogenic testing of the assembled flight model unit.
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David J. Purll, Daniel R. Lobb, Andrew R. Barnes, R. Gordon Talbot, Stephen Rolt, David J. Robertson, Martin F. Closs, Maurice te Plate, "Flight model performance of the integral field unit for the James Webb Space Telescope's near-infrared spectrograph", Proc. SPIE 7739, Modern Technologies in Space- and Ground-based Telescopes and Instrumentation, 773917 (19 July 2010); doi: 10.1117/12.857737; https://doi.org/10.1117/12.857737
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