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)

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

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

This system is more than 20 years old and is being phased out and replaced with a new, custom-built spectrometer.

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).

Laboratory Spectrometers (Mossbauer)

Austin Science drive and electronics with a CO2Kr detector tube and 20 millicurie Co57 source. 1024 channel analyzer.

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 business server concept with X-terminals on each user's desk. The laboratory spectrometers feed data in real time to the central machine. Users can monitor spectrometer functions and data from their offices or even from remote locations. Imaging spectroscopy data are huge. We maintain many tens of gigabytes of data, often analyzing many gigabytes at a time. The central server concept maintains large disk drives, read/write optical, and CD-ROM disk drives to store data. The analysis flow of huge data volumes is kept off the network. Users displaying images on their screens is a very small volume compared to the I/O requirements of imaging spectroscopy data analysis.

We are currently using an HP Itanium 2 server with 4 GBytes RAM, 9 read/write magneto-optical disks (six 5.2 Gbyte drives, three 9.1 Gbyte), CD-ROM/DVD drive, DAT DDS3, 2.2 TBytes hard disk space. The machine has delivers more than 970 MFLOPS per cpu (we have 2 cpus) with our spectral analysis software. This speed allows us to analyze for about 300 materials in a 614x1024-pixel imaging spectroscopy (NASA AVIRIS) data set in about 10 minutes.

Field Spectrometers

We are currently using two 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 Chamber

Our environment chamber allows cooling of samples to liquid cryogenic temperatures (typically liquid Nitrogen- LN₂= 77 K) under vacuum conditions. Vacuum feed throughs allow frost growth and sample creation/manipulation. Temperature and pressure sensors monitor the sample and its environment. The chamber is 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 soon to allow measurement to the far-IR.

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 January 23, 2003.