Compact hyperspectral instruments

Abstract

This presented study is initiated in the frame of CNES advanced studies. It aims at providing a better understanding of driving parameters for this type of instruments, and exploring suitable, very compact hyperspectral instruments based on grating spectrometers.First a scalar model for multiblazed gratings is developed, and confronted with more detailed diffraction models.The spectral band is in the range of 400-2500 nm, with a spectral resolution of about 10 nm width. The Ground Sampling Distance (GSD) shall be between 10 and 15m, the Field of View (FOV) shall be larger than 8km, the orbit Height is 550km.Three types of instruments are proposed, a common spectrometer with a unique detector, a common spectrometer working in diffraction order 1 for the SWIR, and 2 for the VIS spectral band, and 2 spectrometers within field separa tion.For each instrument the grating blazed profile is optimized, the key instruments parameters computed, and an optical configuration is proposed.The study shows compactness optimization with these three instrument concepts, thanks to an entrance pupil diameter reduction along with better grating diffraction efficiency