Mr. Patrice Delpet Profile

Patrice Delpet

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Proceedings Article | 12 July 2023 Open Access

CHIME's Hyperspectral Imager (HSI): status of instrument design and performance at PDR

P. Buschkamp, J. Hofmann, D. Rio-Fernandes, P. Haberler, M. Gerstmeier, C. Bartscher, S. Bianchi, P. Delpet, H. Weber, H. Strese, J. Nieke

Proceedings Volume 12777, 1277737 (2023) https://doi.org/10.1117/12.2690341

KEYWORDS: Equipment, Spectroscopy, Calibration, Sun, Design and modelling, Tunable filters, Optical filters, Glasses, Spectral calibration, Signal to noise ratio

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CHIME, the Copernicus Hyperspectral Imaging Mission for the Environment, is one of six new missions that the EU and ESA are developing to expand the current suite of Copernicus Sentinels. The CHIME mission will provide systematic hyperspectral images to map changes in land cover and help sustainable agricultural practices. The contract for the development of two CHIME Satellites has been awarded in November 2020 to Thales Alenia Space France as Industrial Prime together with OHB Germany as Instrument Prime responsible for the novel Hyperspectral Imager (HSI). Compared to the two hyperspectral precursor missions, EnMAP (DLR) and PRISMA (ASI), CHIME will provide an enhancement allowing continuous and fully operational hyperspectral mapping of the Earth’s surface. The Hyperspectral Imager (HSI) on both satellites is a high-performance pushbroom imaging spectrometer type of instrument. Each instrument records ~130km of swath at 30m x 30m ground sampling. The spectral sampling interval is 10nm, covering a continuous spectral range from 400 nm to 2500 nm. A high performance Three Mirror Anastigmat (TMA) type telescope with wide-band coated optics collects the light reflected from ground and images it to three highly linear radiometric responsive and almost distortion-free spectrometers attaining very good spectral stability. All optical units are mounted to a torus-like carbon fiber (CFRP) optical bench structure providing the necessary line of sight stability. The electro-optical back end is based on passively cooled Teledyne CHROMA-D digital readout detectors creating robust margin in the predicted Signal-to-Noise performance. In flight, the HSI can be calibrated via on-board devices and using reference targets outside the spacecraft. We present the design of the instrument payload at the stage of the Preliminary Design Review (PDR) mid 2022. We show the predicted instrument performance and discuss several design aspect highlights, like the carbon-fiber torus optical bench and the novel spectral calibration unit based on a combination of diffused sun illumination and absorption glass filters.

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