THE U.S. GEOLOGICAL SURVEY SPECTRAL LIBRARY VERSION 7

The USGS has assembled a library of spectra measured with laboratory, field, and airborne imaging spectrometers. The spectrometers used, cover wavelengths from the ultraviolet to the far infrared (0.2 to 200 microns), and include several ASD (PANalytical) field spectrometers, a Nicolet Fourier Transform Infrared (FTIR) spectrometer, and a modified Beckman 5270 spectrophotometer. Laboratory samples of specific minerals, plants, chemical compounds, and man-made materials were measured. In many cases, samples were purified, so that unique spectral features of these materials could be related to their chemical structure. These spectro-chemical links are important for interpreting remote sensing data collected in the field or from an aircraft or spacecraft. This library also contains physically constructed, as well as mathematically computed, mineral mixtures. Measurements of rocks and soils, and natural mixtures of minerals, have been made with laboratory and field spectrometers. Extensive metadata files are available for each spectrum, providing information on the origin, composition, mineral impurities, and spectral purity of the samples based on XRD, SEM, and/or petrographic measurements. Note that a high-resolution Next Generation ASD FS4 instrument was used to re-measure 60 mineral samples, which were used in past studies to map imaging spectrometer data. These new measurements have high signal-to-noise ratio and a spectral resolution of 6 nm in the SWIR, which is fine enough for direct comparison with the latest generation of imaging spectrometers (e.g., AVIRIS NG). Version 7 will contain spectra of nearly 1300 minerals (including grain size series of selected minerals measured with an ASD spectrometer), 200 soil and mineral mixtures, 12 mineral coatings, 24 liquids, over 300 organic compounds, nearly 300 artificial materials, and nearly 300 plants. This represents an increase of 1100 spectra over our previous version 6, released in 2007. In total, the new version of the library will contain nearly 2300 spectra.