Compact airborne spectrographic imager (CASI)

Abstract

A novel instrument, the Compact Airborne Spectrographic Imager (CASI), which is capable of operating in light aircraft and acquiring visible and near infrared imagery in digital form, is described. The instrument consists of the sensor head, instrument control unit, and power supply module, together with a monitor and keyboard. An f/4 reflection-grating spectrograph is coupled to a CCD (charge coupled device) area sensor, providing a resolution of 578 spatial pixels; the spectrum from 450 nm-950 nm for each spatial pixel is dispersed across 288 spectral pixels. To achieve manageable data rates, two operating modes are defined: multispectral imaging mode, which provides maximum spatial resolution for a limited number of spectral bands, and multispectrometer mode, in which full spectra are collected for a limited number of points in the scene. Flight data may be played back on the instrument itself, or on a PC for calibration and transcription to files for image processing.