OARS ? A new system for mapping surface mineralogy simultaneously with airborne geophysics

Abstract

The Operational Airborne Research Spectrometer (OARS) is a novel hyperspectral profiling reflectance spectrometer developed by the Commonwealth Scientific and Industrial Research Organisation (CSIRO) and Fugro Airborne Surveys (FAS) to examine alternative means to collect and deliver exploration data, based on the principles of reflectance spectroscopy. OARS is a component of CSIRO's "Airborne Mineralogy" concept. OARS can be integrated with other airborne geophysical instruments that principally collect magnetic, gamma-ray spectrometry and digital elevation data, and can be flown simultaneously on exactly the same flight lines. OARS will measure ground reflectance spectra from contiguous 8-m pixels from an altitude of 80 m. After data processing, interpolated images of relative mineral abundance can be reconstructed using differential GPS (DGPS) positioning data to produce a variety of mineralogical maps. The OARS system consists of a downward and an upward-looking spectrometer. Each spectrometer covers 190 spectral channels in the visible to short-wave infrared range, with an average spectral resolution of 12 nm. This wavelength range allows OARS to map most species of phyllosilicates, clays, sulphates, carbonates and iron oxides, that occur in alteration zones, regolith and host rocks. Green and dry vegetation can also be identified. A CCD camera (Charge Coupled Device ? Silicon Array) allows monitoring of the flight path while flight attitude sensors and DGPS are used for geo-location. The instrument was first tested in late 1998. Subsequent test surveys in early 1999, over a more challenging geological area in NW Australia, verified its ability to deliver new mineralogical data and its capability as part of an integrated system incorporating magnetic and gamma-ray spectrometry surveying. The resulting case study shows that this line profiling spectrometer can deliver useful interpolated mineral maps with potential synergistic benefits from co-registered magnetic and gamma ray images.