
The State of the Art in Imaging Spectroscopy Materials Mapping

Detection and mapping of minerals, vegetation species, chemicals,
liquids, and solids is being done through the field of imaging
spectroscopy. Imaging spectrometers are deployed on aircraft, spacecraft
(throughout the Solar System) in the field, and in laboratories. Imaging
spectrometers collect a spectrum at each image pixel with enough spectral
resolution to to resolve absorption and emission features in compounds,
whether crystalline or amorphous solids, liquids and gases. What
can be detected remotely is mainly a function of spectral range and
resolution. Analysis of imaging spectrometer data sets is quite complex
and the most advanced system system in existence is the Tetracorder
system first described in detail in Clark et al. 2003.

Tetracorder is in use analyzing data from all over the Solar System,
including mapping ice and other compounds on icy satellite surfaces in
the Saturn and Jupiter systems, minerals on Mars, and was critical in
making the discovery of widespread water on the Moon possible. Tetracorder
is used for mapping ecosystems, and in rapid response to environmental
disasters. It was used in assessing the environmental damage from the
World Trade Center disaster and the the 2010 Deepwater Horizon oil spill
in the Gulf of Mexico.

Tetracorder uses multiple algorithms, including spectral fitting
procedures to identify materials, and derives feature strengths (relative
abundance) of those materials. It has demonstrated discrimination of grain
sizes for some materials using the shape of the absorption features. The
grain sizes and feature strengths can then be fed into radiative transfer
models to derive component abundances.

Tetracorder 5.x uses the U.S. Geological Survey digital spectral
library splib06a (Clark et al., 2007) plus additional spectra.
The native and convolved spectral libraries are maintained on guthub
(__________________).

Tetracorder 5.x+ adapts to both environmental conditions as well
as instrument capability. Previous versions had to be adapted by an
expert spectroscopist for each sensor and environment the data came
from. Tetracorder produces maps of hundreds of materials, including
chemical substitutions in some minerals. Imaging chemistry
remotely, whether across a canyon, from a high point overlooking
an environmental disaster, or a studying remote planets. This is now
possible. Further, Tetracorder results are made into custom color-coded
maps automatically.



Clark et a., 2003 is availabel as a pdf in:a AAA.REFERENCE.documents.dir

Papers that use tetracorder can reference the following papers. 

Clark, R.N., Swayze, G.A., Livo, K.E., Kokaly, R.F., Sutley, S.J., Dalton,
J.B., McDougal, R.R., and Gent, C.A., 2003, Imaging spectroscopy:
Earth and planetary remote sensing with the USGS Tetracorder and
expert systems, Journal of Geophysical Research, Vol. 108(E12), 5131,
doi:10.1029/2002JE001847, p. 5-1 to 5-44.

Clark, R.N., Swayze, G.A., Wise, R., Livo, E., Hoefen, T., Kokaly,
R., Sutley, S.J., 2007, USGS digital spectral library splib06a:
U.S. Geological Survey, Data Series 231.




This paper evaluates the performance of the tetracorder core algorithm and
is a knowledge base for strategy on which spectral features to use in
the tetracorder expert system.

Swayze, G.A., Clark, R.N., Goetz, F.H., Chrien, T.G., and Gorelick, N.S.,
2003, Effects of spectrometer band pass, sampling, and signal-to-noise
ratio on spectral identification using the Tetracorder algorithm:
Journal of Geophysical Research (Planets), vol. 108(E9), 5105, doi:
10.1029/2002JE001975, 30 p.
