Remote Laser Induced Breakdown Spectroscopy (LIBS) + Laser Induced Thermal (Infrared) Emission (LITE) Detection System for In-Situ Surface Contaminant Mapping and Identification

With the goal of enabling rapid and comprehensive standoff sensing of chemical compounds, we proposed to develop a compact, integrated, optical sensing LIBS + LITE instrument with high spectroscopic information content for in situ reconnaissance and characterization of surface contamination mapping and identification. This proposed LIBS + LITE instrument is an integrated system with a LIBS + LITE detector unit carried by an unmanned aerial system (UAS) whose the flight path will be synchronized with the vehicle-based excitation laser beam to probe the operational surface. LIBS + LITE is a novel concept that incorporates a suite of two advanced optical spectroscopy technologies: UV-visible-NIR (UVN) Laser Induced Breakdown Spectroscopy (LIBS) and an additional groundbreaking capability of a mid-IR laser-induce Thermal Emission (LITE) spectroscopy. LITE is the first and only mid-IR emission spectroscopy without the need of any sample preparation that can be used as a rapid, in situ, and standoff chemical characterization probe in the field applications. Combined with multi-elemental analysis of UVN LIBS emission, this novel system has the potential to offer a rapid, comprehensive, and robust chemical characterization of surface targets of from standoff distance. Phase I studies clearly show LIBS+ LITE as a viable rapid in-situ analytical tool for offering sub-millisecond analysis and high specificity and sensitivity of Army reconnaissance mission related chemical compounds. The intense and distinctive LIBS + LITE spectral features of the surface hazardous contaminants, such as chemical warfare agent (CWA) simulants DMMP and Malathion, can be readily and unambiguously distinguished from the various background signals. The phase I studies estimated the possible detection limit of this proposed optical technology to be in the range of 0.6-6 g/m2 and 100-1000 ppm. Based on our previous experience in designing and operating the bench top LIBS + LITE prototype and the phase I studies, we are able to design an integrated LIBS + LITE instrument with simple and robust scheme and a small size, weight, and power consumption (SWaP) to meet the stringent requirement of an operational UAS. The spectroscopy subsystems utilize reflective optics to couple light from the interrogation sample ensuring co-registered views of the identical sample region. Implemented as modules, LIBS and LITE detection units share common excitation elements that enable packaging into a relatively small form factor (18 X 10 X 10 cm3) with estimated 3.7 pounds weight. In Phase II, to construct the prototype instrument, we will test the actual performance of each individual subsystem base on the finding and designs in Phase I studies, including excitation laser, collection optics, spectrometers, detectors, system integration and control software with data process algorithm. The whole system will be tailored to Army’s reconnaissance missions that require ruggedness and small SWaP.