Predict and simulate final optical performances of TMAs: application to the NIRSpec instrument

François Riguet

doi:10.1117/12.981203

18 December 2012 Predict and simulate final optical performances of TMAs: application to the NIRSpec instrument

François Riguet

Proceedings Volume 8550, Optical Systems Design 2012; 85501A (2012) https://doi.org/10.1117/12.981203
Event: SPIE Optical Systems Design, 2012, Barcelona, Spain

Abstract

The near-infrared spectrograph (NIRSpec) is a complex instrument that will be launched on board the James Webb Space Telescope (JWST). It is composed of three three-mirror anastigmats (TMAs) made of silicon carbide (SiC). Sagem REOSC has been in charge of the mirror polishing, coating, alignment and testing, as well as cryogenic testing. The performance level and the alignment constraints, along with the polishing and alignment processes, have led to the set up of a model to accurately predict the final performances of each TMA, and minimize the risk of vignetting. The model has then been fitted to the measured parameters obtained after alignment (wavefront error, magnification or focal length...) to get an accurate modelization of the actual performances, and allow their evaluation on the full field of view. The model has been finally delivered with each TMA, as a basis for the instrument performance simulator. We will show a good correlation between the predicted performance (before alignment, obtained from individual mirror data) and the final performance (after alignment), as well as a very good fit between the as-built models and the actual TMAs.

Citation Download Citation

François Riguet "Predict and simulate final optical performances of TMAs: application to the NIRSpec instrument", Proc. SPIE 8550, Optical Systems Design 2012, 85501A (18 December 2012); https://doi.org/10.1117/12.981203

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