USGS Spectroscopy Lab

USGS Denver Spectroscopy Lab Facilities

from http://speclab.cr.usgs.gov

(Use of trade names are for descriptive purposes only and does not constitute endoresment by the USGS or spectroscopy lab personnel.)

Laboratory Spectrometers (UV to NIR)

(retired) Beckman 5270 spectrophotometer, custom modified in-house to control all functions. The system is described in Clark, R. N., King, T. V. V., Klejwa, M., Swayze, G. A., Vergo, N., 1990, High spectral resolution reflectance spectroscopy of minerals: Journal of Geophysical Research, 95, 12653-12680.

Wavelength Range: 0.2 to 3.0 microns,
   (computer selectable spectral resolution):
        0.2  to 0.85 microns region: 0.008 to 0.00005 microns
        0.85 to 4.00 microns region: 0.032 to 0.0003  microns

Some measurements contained in our spectral libraries were obtained with this system.

We currently use high resolution versions of of ASD spectrometers and our field spectrometers in the lab for 0.35 to 2.5 micron work.

Laboratory Spectrometers (NIR, MIR to FIR)

Nicolet model Magna 760 FTIR spectrophotometer (new 1998). With our current equipment, we have the capability to measure from about 6666 to 67 inverse cm (1.5 to 150 microns). Wavelength accuracy is ~0.1 inverse cm. Resolution is selectable from 0.125 to 32 inverse cm. This system has greater signal to noise than our older model 740 system. We also have more detectors, including liquid nitrogen cooled InSb, allowing even greater signal to noise.

We typically measure reflectance spectra with 4 inverse cm resolution (sampling at 2 inverse cm).

Sample Collections

The complete collection of samples of Graham Hunt and Jack Salisbury (spectra published in Modern Geology series of papers). Approximately 2100 samples of 400 minerals.

Well-characterized samples from the Source Clay Minerals Repository, University of Missouri (26 samples).

Complete set of Wards Scientific rocks (1000 samples), including many near-gem quality specimens.

Our own collection of samples, the GDS series includes over 600 samples. The collection includes minerals, mineral mixtures, environmental and man-made materials.

Selected samples from the National Museum of Natural History and the British Museum.

Computer Facilities

We use a central server concept with linux desktops to serve X-windows on each user's desk. We maintain over 100 terabtes of disk storage, often analyzing many gigabytes of imaging spectrometer data at a time. The central server concept maintains large disk drive raid arrays to store data.

We are currently using an HP Itanium server with 8 GBytes RAM and quad core linux servers with 32+ GBytes of RAM.

Field Spectrometers

We are currently using three ASD FR (0.4 - 2.5 micron) field spectrometers to measure samples and provide for in situ calibration of surface reflectance for terrestrial imaging spectroscopy studies. They also serve as laboratory spectrometers when rapid spectra are needed. In calibrating standards in the field, we usually obtain hundreds of spectra at a site and average them to provide an average spectrum similar to what the remote sensing instruments measure. We find that no field instrument can have the quality of a stable laboratory instrument because of temperature drifts and rapidly changing atmospheric absorptions. Thus we also obtain field samples which we measure on our laboratory instruments to confirm spectral details and to provide information for removing artifacts from the field data. This two step approach is our best assurance of precise spectra.

Environment Chambers

Our environment chambers allows cooling of samples to liquid cryogenic temperatures (typically liquid Nitrogen- LN₂= 77 K) under vacuum conditions or pressure. Vacuum feed throughs allow frost growth and sample creation/manipulation. Temperature and pressure sensors monitor the sample and its environment. The chambers are used to simulate environments in the outer solar system. Spectrometers measure the sample from 0.4 to 2.5 microns currently, with mating to our Nicolet to allow measurement to 5.1 microns through a saphire window. Room pressure measurements are also made in a 1-bar dry nitrogen atmosphere allowing spectral measurements from the ultraviolet to 15.5 microns at 76 Kelvin and higher.

U.S. Geological Survey, a bureau of the U.S. Department of the Interior
This page URL= http://speclab.cr.usgs.gov/facilities.html
This site is maintained by: Dr. Roger N. Clark rclark@usgs.gov
Last modified March 30, 2010.