http://arxiv.org/abs/2208.04876
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.
G. Giardino, R. Bhatawdekar, S. Birkmann, et. al.
Wed, 10 Aug 22
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Comments: 7 pages, 6 figures – to appear in Proceedings of SPIE conference “Space Telescopes and Instrumentation 2022: Optical, Infrared, and Millimeter Wave”
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