Optical design and optimization of a hyperspectral-stereo camera for CubeSat

The Hyperspectral Stereo-Camera for CubeSat (HSCC) is a novel instrument for remote sensing able to simultaneously extract 4D information, three spatial and one spectral, using the two channels of a pushbroom stereo camera coupled to a suitable spectral filter. HSCC is designed to be a very compact instrument, compatible with CubeSat applications, to be suitable for planetary exploration as well for terrestrial environmental monitoring. In this paper we describe the optical design of HSCC, show its nominal optical performance, and give indications about the performed optimizations. The system consists of a very compact innovative layout (1-Unit CubeSat) aimed at optimizing overall dimensions and masses, in which the two stereo channels, looking forward and backward along track with respect to nadir, share both a three-mirror anastigmat telescope and a bidimensional detector. The spectral analysis of the observed target is realized by the combination of the pushbroom scan and a linear variable filter put in front of the sensor: in fact, each linear field of view projected on the sensor moves along the filter dispersion direction following the satellite orbit and is spectrally selected by the local filter bandpass. The spectral selection coupled to the three-dimensional scene obtained by the stereoscopic view provides a global 4D result, allowing to get simultaneously from a single instrument a complete set of information of the observed surface usually attainable by at least two different instruments, so avoiding the typically very cumbersome cross-calibration and co-registration issues.