Raman efficiencies of natural rocks and minerals: performance of a remote Raman system for planetary exploration at a distance of 10 meters.
Raman spectroscopy is a powerful technique for materials analysis, and we are developing and analyzing a remote Raman system for use on a planetary lander or rover. We have acquired data at a distance of 10m from a variety of geologic materials using different instrument designs. We have employed a pulsed laser with both an ungated detector and a gated detector. A gated detector can reduce long-lived fluorescence while still collecting all Raman signal. In order to design a flight instrument, we need to quantify how natural surfaces will respond to laser stimulus. We define remote Raman efficiency of natural surfaces as the ratio of radiant exitance leaving a natural surface to the irradiance of the incident laser. The radiant exitance of a natural surface is the product of the sample radiance, the projected solid angle, and the full-width-half-maximum of the Raman signal. We have determined the remote Raman efficiency for a variety of rocks and minerals. The best efficiencies are achieved for large, clear, single crystals that produce the most radiant exitance, while darker fine-grained mineral mixtures produce lower efficiencies. By implementing a pulsed laser, gated detector system we have improved the signal detection and have generally decreased the integration time necessary to detect Raman signal from natural surfaces.
Stopar
Julie D
JD
Hawaii Institute of Geophysics and Planetology, University of Hawaii, 1680 East-West Road, Post 504, Honolulu, HI 96822, USA. jstopar@higp.hawaii.edu
Lucey
Paul G
PG
Sharma
Shiv K
SK
Misra
Anupam K
AK
Taylor
G Jeffrey
GJ
Hubble
Hugh W
HW
D003627:Data Interpretation, Statistical; D005118:Extraterrestrial Environment; D018535:Mars; D012371:Robotics; D017640:Silicates / Q000737:chemistry; D013059:Spectrum Analysis, Raman / Q000295:instrumentation
D017640:Silicates