Performance of the Imaging Spectral Signature Instrument (ISSI) breadboard

摘要

With hyperspectral pushbroom imaging spectrometers it is possible to identify ground pixels by their spectral signature. The Imaging Spectral Signature Instrument (ISSI) concept performs optical on-board processing of the hyperspectral data to identify pixels with a pre-defined and programmable spectral signature. An aircraft compatible breadboard of ISSI has been developed and manufactured. It consists of an objective, which images an object line on the input slit of a first imaging spectrograph, which disperses each pixel of the object line into its spectral content on a liquid-crystal spatial light modulator. This component is programmed with a spatial transmission behaviour, which is constant along the spatial pixels and equal to the spectral filter vector of the searched specific signature along the spectral pixels. A second inverted spectrograph re-images the transmitted flux into a line of pixels on a CCD detector. ISSI operates at wavelengths between 470 nm and 900 nm. The spectral filter vector can be selected for 800 spatial pixels with a spectral resolution of better than 4 nm and almost 8 bit modulation capability. ISSI effectively performs the spectral angle mapping (SAM) operation used in hyperspectral data processing. The signatures are acquired with ISSI in a spectrometer operating mode. The breadboard has undergone a test program consisting of calibration and verification of the spectral, spatial and radiometric performance and object identification capability.