REGIONAL MAPPING OF PLANETARY SURFACES WITH IMAGING SPECTROSCOPY

We present a method to determine spectral differences and compositiona l variability of planetary surfaces when remotely sensed by means of i maging spectroscopy instrumentation. The quantity frequently measured in remote sensing of planetary bodies in the 0.3-2.5 mu m spectral ran ge is the reflectance spectrum and it is used to study the mineralogic composition of the surface being sensed. Very often, however, this qu antity is difficult to measure owing to lack of knowledge either of at mospheric extinction or of analogous ar spectra. The method we describ e allows all the in a surface having spectral similarity, to be identi fied and does not require the reflectance spectrum measured, taking fu ll advantage of imaging spectroscopy and classification methods. In pr actice, all the sco spectra of the image are divided by the spectrum o f a pixel (or an average spectrum) tak-en in the image itself. Ire Swa y, both the instrument and the atmospheric transfer functions are elim inated and it is possible to compare the spectra with one another. The se new relative spectra are then classified using a clustering algorit him in order to recognize spectral similarities. The final result is a map showing all the regions in the image having similar spectra which can be linked to the mineralogical composition of the surface under T he method has been applied to Earth-based observations of the Moon but can be equally used with; other high spatial imaging spectroscopy dat a provided by future interplanetary missions. (C) 1997 Published by El sevier Science Ltd. All rights reserved.