Paper

Optical throughput and sensitivity of JWST NIRSpec

Alves de Oliveira, C, Zeidler, P, Proffitt, C, Giardino, G, Lopez-Caniego, M, Luetzgendorf, N, Jakobsen, P, M Te Plate, Sirianni, M, Manjavacas, E, Rawle, T, Boeker, T, Birkmann, S M, Bhatawdekar, R, Ferruit, P, Kumari, N

2022

Overview

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 micron, and exceed +30%, below 2 micron. 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.

• Publisher: Cornell University Library, arXiv.org
• Subject: Infrared spectra / James Webb Space Telescope / Low noise / Modelling / Near infrared radiation / Point spread functions / Space telescopes / Spectrum analysis