In-flight performance and calibration of the grating wheel assembly sensors (NIRSpec/JWST)

Catarina Alves de Oliveira; Nora Lützgendorf; Peter Zeidler; Giovanna Giardino; Pierre Ferruit; Nimisha Kumari; Timothy Rawle; Stephan M. Birkmann; Torsten Böker; Charles Proffitt; Marco Sirianni; Maurice Te Plate

doi:10.1117/12.2629911

27 August 2022 In-flight performance and calibration of the grating wheel assembly sensors (NIRSpec/JWST)

Catarina Alves de Oliveira, Nora Lützgendorf, Peter Zeidler, Giovanna Giardino, Pierre Ferruit, Nimisha Kumari, Timothy Rawle, Stephan M. Birkmann, Torsten Böker, Charles Proffitt, Marco Sirianni, Maurice Te Plate

Author Affiliations +

Proceedings Volume 12180, Space Telescopes and Instrumentation 2022: Optical, Infrared, and Millimeter Wave; 121803S (2022) https://doi.org/10.1117/12.2629911
Event: SPIE Astronomical Telescopes + Instrumentation, 2022, Montréal, Québec, Canada

Conference Poster

Abstract

The Near-Infrared Spectrograph (NIRSpec) on board of the James Webb Space Telescope will be the first multiobject spectrograph in space offering ∼250,000 configurable micro-shutters, apart from being equipped with an integral field unit and fixed slits. At its heart, the NIRSpec grating wheel assembly is a cryogenic mechanism equipped with six dispersion gratings, a prism, and a mirror. The finite angular positioning repeatability of the wheel causes small but measurable displacements of the light beam on the focal plane, precluding a static solution to predict the light-path. To address that, two magneto-resistive position sensors are used to measure the tip and tilt displacement of the selected GWA element each time the wheel is rotated. The calibration of these sensors is a crucial component of the model-based approach used for NIRSpec for calibration, spectral extraction, and target placement in the micro-shutters. In this paper, we present the results of the evolution of the GWA sensors performance and calibration from ground to space environments.

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Catarina Alves de Oliveira, Nora Lützgendorf, Peter Zeidler, Giovanna Giardino, Pierre Ferruit, Nimisha Kumari, Timothy Rawle, Stephan M. Birkmann, Torsten Böker, Charles Proffitt, Marco Sirianni, and Maurice Te Plate "In-flight performance and calibration of the grating wheel assembly sensors (NIRSpec/JWST)", Proc. SPIE 12180, Space Telescopes and Instrumentation 2022: Optical, Infrared, and Millimeter Wave, 121803S (27 August 2022); https://doi.org/10.1117/12.2629911

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