The FIREBall-2 UV sample grating efficiency at 200-208nm

S. Quiret; B. Milliard; R. Grange; G. R. Lemaitre; A. Caillat; M. Belhadi; A. Cotel

doi:10.1117/12.2056972

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25 July 2014 The FIREBall-2 UV sample grating efficiency at 200-208nm

S. Quiret, B. Milliard, R. Grange, G. R. Lemaitre, A. Caillat, M. Belhadi, A. Cotel

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Proceedings Volume 9144, Space Telescopes and Instrumentation 2014: Ultraviolet to Gamma Ray; 914432 (2014) https://doi.org/10.1117/12.2056972
Event: SPIE Astronomical Telescopes + Instrumentation, 2014, Montréal, Quebec, Canada

Abstract

The FIREBall-2 (Faint Intergalactic Redshifted Emission Balloon-2) is a balloon-borne ultraviolet spectro-imaging mission optimized for the study of faint diffuse emission around galaxies. A key optical component of the new spectrograph design is the high throughput cost-effective holographic 2400 ℓ =mm, 110x130mm aspherized reflective grating used in the range 200 - 208nm, near 28°deviation angle. In order to anticipate the efficiency in flight conditions, we have developed a PCGrate model for the FIREBall grating calibrated on linearly polarized measurements at 12° deviation angle in the range 240-350nm of a 50x50mm replica of the same master selected for the flight grating. This model predicts an efficiency within [64:7; 64:9]±0:7% (S polarization) and [38:3; 45]±2:2% (P-polarization) for the baseline aluminum coated grating with an Al₂O₃ natural oxidation layer and within [63:5; 65] ±1% (S-polarization) and [51:3; 54:8] ±2:8% (P-polarization) for an aluminum plus a 70nm MgF₂ coating, in the range 200 - 208nm and for a 28°deviation angle. The model also shows there is room for significant improvements at shorter wavelengths, of interest for future deep UV spectroscopic missions.

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S. Quiret, B. Milliard, R. Grange, G. R. Lemaitre, A. Caillat, M. Belhadi, and A. Cotel "The FIREBall-2 UV sample grating efficiency at 200-208nm", Proc. SPIE 9144, Space Telescopes and Instrumentation 2014: Ultraviolet to Gamma Ray, 914432 (25 July 2014); https://doi.org/10.1117/12.2056972

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