The CASI is a newly developed second generation imaging spectrometer. The CASI operates in the 400-900nm spectral range, providing a spectral resolution of 1.8 urn and an image of 578 pixels. The CASI is a flexible and portable remote sensor that can be used in both the laboratory and in the field. This paper discribes briefly the elementary construction and the operating mode of the CASI. Its special features are also included.