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arXiv · 2608.13257

Optical concept model of the future cosmology project BISOU

Morgane Loquet Le Gall·Bruno Maffei·Pierre Guiot·Creidhe O'Sullivan·Neil Trappe
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Abstract

We present an optical analysis of BISOU (Balloon Interferometer for Spectral Observations of the primordial Universe), an astronomical balloon-borne pathfinder spectrometer developed as part of a preparatory study for a future space mission aiming at measuring spectral distortions of the cosmic microwave background (CMB). The BISOU optical system is based on a differential polarizing Fourier Transform Spectrometer (FTS) that receives inputs from both a sky-facing telescope and an internal calibration source. The FTS focal planes are equipped with bolometric detectors coupled to multimode feed horns, with distinct focal planes dedicated to the low (90 - 300GHz) and high (0.3 - 1.5THz) frequency bands. The optical analysis first relies on ray-tracing simulations to establish the overall configuration of the system, before proceeding to more advanced Gaussian beam and physical optics analyses.

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Morgane Loquet Le Gall, Bruno Maffei, Pierre Guiot, Creidhe O'Sullivan, Neil Trappe. 2026-08-13. Optical concept model of the future cosmology project BISOU. https://doi.org/10.1117/12.3098705%2010.1117%2F12.3098705

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