Aviris Evaluation For Classification Of Rock Outcrops

Abstract

Ivan PippiIstituto di Ricerca sulle Onde Elettromagnetiche del Consiglio Nazionale delle RicercheVia Panciatichi, 64 - 50127 Firenze - ItaliaABSTRACTA new airborne imaging spectrometer has been developed by the Jet Propulsion Laboratory to exploit many earth resources. The apparatus utilizes 210 adjacent spectral bands ranging from 0.40 to 2.45 um.During the first measurement campaign in the summer 1987, the spectrometer was flown over a site containing both hydrothermally altered and unaltered rocks well exposed at the surface.The related radiometrically corrected image set has been available to the investigators. Using the software developed at our Institute, a set of images of the site in any of the 210 spectral bands or the spectral signature of any single pixel can be displayed.In addition particular attention is paid to evaluate the data accuracy and the atmospheric effects utilizing the LQWTRAN 6 computer code. First results of rock outcrops classification are presented and discussed.1. INTRODUCTIONThe AVIRIS (Airborne Visible Infrared Imaging Spectrometer) l is a prototype for the HIRIS (High-Resolution Imaging Spectrometer)2 planned for launch in the mid 1990s on the polar platform.In the first season of operation during the summer 1987, the AVIRIS was flown on board of the NASA U-2 aircraft acquiring data over more than 30 different sites located in the United States. A site was located in the Cuprite mining district in western Nevada, in order to evaluate the ability of this instrument to classify the rock outcrops.Spectral features for minerals are associated with electronic transitions in transition elements, mainly iron, in the visible - near infrared region and vibrational modes in the region beyond 1.5 jam. Vibrational features, generally overtone bending-stretching vibrations, are exhibited by minerals bearing Al-OH, Mg-OH, COa, and SO4 constituents.2. INSTRUMENT DESCRIPTIONThe sensor was designed to acquire images with a swath of about 10 km from the NASA U-2 or ER-2 aircrafts, flying at an altitude of 20 km with a ground-track velocity of 740 km/hr. Since the pilot has a full-time job only flying the aircraft, the instrumentation is completely under computer control except for the power and record functions.