Optical throughput and sensitivity of JWST NIRSpec

Giovanna Giardino; Rachana Bhatawdekar; Stephan M. Birkmann; Pierre Ferruit; Timothy Rawle; Catarina Alves de Oliveira; Torsten Böker; Peter Jakobsen; Nimisha Kumari; Marcos López-Caniego; Nora Lützgendorf; Elena Manjavacas; Charles Proffitt; Marco Sirianni; Maurice Te Plate; Peter Zeidler

doi:10.1117/12.2628980

27 August 2022 Optical throughput and sensitivity of JWST NIRSpec

Giovanna Giardino, Rachana Bhatawdekar, Stephan M. Birkmann, Pierre Ferruit, Timothy Rawle, Catarina Alves de Oliveira, Torsten Böker, Peter Jakobsen, Nimisha Kumari, Marcos López-Caniego, Nora Lützgendorf, Elena Manjavacas, Charles Proffitt, Marco Sirianni, Maurice Te Plate, Peter Zeidler

Author Affiliations +

Proceedings Volume 12180, Space Telescopes and Instrumentation 2022: Optical, Infrared, and Millimeter Wave; 121800X (2022) https://doi.org/10.1117/12.2628980
Event: SPIE Astronomical Telescopes + Instrumentation, 2022, Montréal, Québec, Canada

Abstract

To achieve its ambitious scientific goals, the Near-Infrared Spectrograph, NIRSpec, on board the Webb Space Telescope, needs to meet very demanding throughput requirements, here quantified in terms of photon-conversion efficiency (PCE). During the calibration activities performed for the instrument commissioning, we have obtained the first in-flight measurements of its PCE and also updated the modeling of the light losses occurring in the NIRSpec slit devices. The measured PCE of NIRSpec fixed-slit and multi-object spectroscopy modes overall meets or exceeds the pre-launch model predictions. The results are more contrasted for the integral-field spectroscopy mode, where the differences with the model can reach −20%, above 4 μm, and exceed +30%, below 2 μm. Additionally, thanks to the high quality of the JWST point-spread function, our slit-losses, at the shorter wavelength, are significantly decreased with respect to the pre-flight modeling. These results, combined with the confirmed low noise performance of the detectors, make of NIRSpec an exceptionally sensitive spectrograph.

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Giovanna Giardino, Rachana Bhatawdekar, Stephan M. Birkmann, Pierre Ferruit, Timothy Rawle, Catarina Alves de Oliveira, Torsten Böker, Peter Jakobsen, Nimisha Kumari, Marcos López-Caniego, Nora Lützgendorf, Elena Manjavacas, Charles Proffitt, Marco Sirianni, Maurice Te Plate, and Peter Zeidler "Optical throughput and sensitivity of JWST NIRSpec", Proc. SPIE 12180, Space Telescopes and Instrumentation 2022: Optical, Infrared, and Millimeter Wave, 121800X (27 August 2022); https://doi.org/10.1117/12.2628980

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