ABSTRACT
The remote detection of chemicals using remote Raman spectroscopy and laser-induced breakdown spectroscopy (LIBS) is highly desirable for homeland security and NASA planetary exploration programs. We recently demonstrated Raman spectra with high signal-to-noise ratio of various materials from a 430 m distance during daylight with detection times of 1-10 s, utilizing a 203 mm diameter telescopic remote Raman system and 100 mJ/pulse laser energy at 532 nm for excitation. In this research effort, we describe a simple two-components approach that helps to obtain remote Raman and LIBS spectra of targets at distance of 246 m with 3 mJ/pulse in daytime. The two components of the method are: (1) a small spectroscopy system utilizing 76 mm diameter collection optics; and (2) a small remote lens near the target. Remote Raman spectra of various chemicals are presented here with detection time of 1 s. Remote LIBS spectra of minerals using single laser pulse of 3 mJ/pulse energy from a distance of 246 m are also presented. This research work demonstrates a simple approach that significantly improves remote Raman and LIBS capabilities for long range chemical detection with compact low laser power Raman and LIBS systems.
ABSTRACT
Raman spectroscopy is a characterization technique that is able to analyze and detect water or water-bearing minerals, minerals, and organic materials that are of special interest for planetary science. Using a portable pulsed remote Raman system with a commercial 8 in. (203.2 mm) telescope, a frequency doubled Nd-YAG-pulsed laser, and a spectrometer equipped with an intensified CCD camera, we acquired good quality Raman spectra of various materials from a 430 m standoff distance during daylight with detection times of 1-10 s, in a realistic context in which both the exciting source and the detector are part of the same measurement system. Remote Raman spectra at this distance provided unambiguous detection of compounds such as water and water ice, dry ice, sulfur, sulfates, various minerals and organics, and atmospheric gases. This research work demonstrates significant improvement in the remote Raman technique as well as its suitability for solar system exploration.
