Proceedings Article | 12 July 2019
Proc. SPIE. 11180, International Conference on Space Optics — ICSO 2018
KEYWORDS: Diffraction, Point spread functions, Telescopes, Mirrors, Polarization, Sensors, Spectrometers, Distortion, Transmittance, Performance modeling
Tropomi, successfully launched in October 2017, and Sentinel-5, with launch due in 2021, are two pushbroom spectrometers measuring Earth’s radiance from a Low Earth Orbit (LEO) at a high spectral resolution. Both instruments have strongly overlapping spectral channels (UV-VIS, NIR, SWIR-3). While the Tropomi spectrometers are designed with standard slits, all Sentinel-5 channels make use of complex slit assemblies called “slit homogenizers” that aim at mitigating the slit heterogeneous illumination that results from the along track spatial non-uniformity of the observed scenes, and is known to distort the instrument spectral response function (ISRF). The similarity between the two missions will allow, in a few years from now, to evaluate the performance gain resulting from these devices. If their expected success is confirmed, slit homogenizers may become standard components of future space missions. This paper aims at providing a comprehensive, yet as simple and accessible as possible, overview of the slit homogenizer performance. The Sentinel-5 slit homogenizers, based on two parallel mirrors will be discussed, and a new and promising family of slit homogenizer designs will be presented for the first time. The new designs offer several advantages in terms of performance and manufacturability.
