Double-Dispersive Spatio-Spectral Scanning for Hyperspectral Earth Observation

Most instruments for hyperspectral Earth observation rely on dispersive image acquisition via spatial scanning. In such systems, the Earth's surface is scanned line by line while the satellite carrying the instrument moves over it. The spatial and spectral resolutions of the image acquisition are directly coupled via a slit aperture and are thus difficult to adjust independently. Spatio-spectral scanning systems, on the other hand, can acquire 2D, spectrally coded images with decoupled spatial and spectral resolutions. Despite this advantage, they have so far been given little attention in the literature. Simple architectures using variable filters were proposed, but come with significant caveats. As an alternative, we investigated the use of two dispersion stages for spatio-spectral scanning. We provide a theoretical treatment and show by basic experiments that a double-dispersive system provides robust and flexible image acquisition. Based on our results, we suggest a system concept for the implementation of a demonstrator on a small satellite.