A double-dispersive setup for spatio-spectral scanning in hyperspectral Earth observation

In satellite-based hyperspectral Earth observation, spatial scanning of a spectrally dispersed one-dimensional field of view is a common approach. Here, the spatial and spectral resolutions of the image acquisition are directly coupled via a slit aperture and cannot be adjusted independently. Spatio-spectral scanning systems, on the other hand, acquire two-dimensional, spectrally coded images with decoupled spatial and spectral resolutions. As an alternative to the use of variable filters in such systems, we investigated an approach based on two dispersion stages and a variable slit. We give a short theoretical overview and present a first experimental validation with a physically doubled Czerny-Turner laboratory setup. We also consider a virtually doubled setup based on a mirrored slit as a compact alternative. Lastly, we discuss benefits, challenges, and possible applications, focusing on SmallSat-based observation.