Astrometric and wavelength calibration of the NIRSpec instrument during commissioning using a model-based approach

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

doi:10.1117/12.2630069

27 August 2022 Astrometric and wavelength calibration of the NIRSpec instrument during commissioning using a model-based approach

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

Author Affiliations +

Proceedings Volume 12180, Space Telescopes and Instrumentation 2022: Optical, Infrared, and Millimeter Wave; 121800Y (2022) https://doi.org/10.1117/12.2630069
Event: SPIE Astronomical Telescopes + Instrumentation, 2022, Montréal, Québec, Canada

Abstract

The NIRSpec instrument for the James Webb Space Telescope (JWST) is a highly versatile near-infrared spectrograph that can be operated in various observing modes, slit apertures, and spectral resolutions. Obtaining dedicated calibration data for all possible combinations of aperture and disperser is an intractable task. We have therefore developed a procedure to derive a highly realistic model of the instrument’s optical geometry across the entire field of view, using calibration data acquired through only a subset of NIRSpec apertures, which nevertheless allows the light paths within the spectrograph to be accurately computed for all apertures and all observing modes. This parametric instrument model thus provides the basis for the extraction of wavelengthcalibrated spectra from any NIRSpec exposure, regardless of observing mode or aperture used. Optimizing the NIRSpec instrument model and deriving its final wavelength and astrometric calibration was one of the most crucial elements of the NIRSpec commissioning phase. Here, we describe the process of re-fitting the NIRSpec instrument model with in-orbit commissioning data, and present its final performance in terms of wavelength accuracy and astrometric calibration.

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Nora Lützgendorf, Giovanna Giardino, Catarina Alves de Oliveira, Peter Zeidler, Pierre Ferruit, Peter Jakobsen, Nimisha Kumari, Timothy Rawle, Stephan M. Birkmann, Torsten Böker, Charles Proffitt, Marco Sirianni, Maurice Te Plate, and Sangmo Tony Sohn "Astrometric and wavelength calibration of the NIRSpec instrument during commissioning using a model-based approach", Proc. SPIE 12180, Space Telescopes and Instrumentation 2022: Optical, Infrared, and Millimeter Wave, 121800Y (27 August 2022); https://doi.org/10.1117/12.2630069

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