The Near-Infrared Spectrograph (NIRSpec) on board of the James Webb Space Telescope will be the first multi-object 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.
@article{arxiv.2208.05354,
title = {In-flight performance and calibration of the Grating Wheel Assembly sensors (NIRSpec/JWST)},
author = {Catarina Alves de Oliveira and Nora Luetzgendorf and Peter Zeidler and Giovanna Giardino and Pierre Ferruit and Nimisha Kumari and Timothy Rawle and Stephan M. Birkmann and Torsten Boeker and Charles Proffitt and Marco Sirianni and Maurice Te Plate},
journal= {arXiv preprint arXiv:2208.05354},
year = {2022}
}
Comments
To appear in Proceedings of SPIE conference "Space Telescopes and Instrumentation 2022: Optical, Infrared, and Millimeter Wave"