A Novel Hyperspectral Imaging System For Small Satellites

This paper describes a novel approach to hyperspectral imaging that is currently being implemented successfully on a small satellite.The instrument being flown is the Compact High Resolution Imaging Spectrometer (CHRIS) developed at Sira Electro-Optics Ltd. The instrument is flying on PROBA, a small agile satellite, which was launched in October 2001. The PROBA platform is flying in a sun-synchronous polar orbit with an inclination of 97.89degrees. The altitude of the platform varies over a range approximately from 553 to 688 km. The platform period is 96.8min. The apogee of the orbit rotates around the Earth with an approximate 110 day periodicity. The main purpose of the instrument is to provide images of land areas.The platform provides pointing in both across-track and along-track directions, for target acquisition and multi-angle observations, particularly for measurement of the Bi-directional Reflectance Distribution Function (BRDF) properties of selected targets.One of the main novel features of this instrument is the provision of ground motion compensation during imaging in order to increase the integration time of the instrument, increasing the number of spectral bands that can be read and enhancing radiometric resolution. This also results in a smaller instrument, which is more compatible with small satellite dimensions.The instrument covers a spectral range from 400nm to 1050nm, at less than or equal to11nm resolution. The spatial sampling interval at perigee is approximately 17m. In this mode it is possible to read out 19 spectral bands. The locations and widths of the spectral bands are programmable. Selectable on-chip integration can increase the number of bands to 63 for a spatial sampling interval of 34m. The swath width imaged is 13km at perigee.The programme is operating successful and demonstrates the success of the mission and the utility of the platform and instrument.