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The authors report on an approach for simultaneous monitoring of multigas pollutants based on fluorescence emission of trace gases, induced by the filamentation of intense femtosecond laser pulses in air. The high intensity inside a filament can dissociate the gas molecules into small fragments which emit characteristic fluorescence. This method is illustrated for simultaneously sensing atmospheric trace gases, methane and acetylene. The spectra of an “unknown” mixture were analyzed by using a genetic algorithm, showing good concentration agreement with the experimental results within an error of 25%.

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In order to reduce the serious problem associated with the mining of important supply/communication roads by hostile parties during peacekeeping operations, the Canadian Department of National Defence has recently begun the development of a multi-sensor teleoperated mine detection vehicle, the Improved Landmine Detection Capability (ILDC) . One sensor identified as a serious candidate for that project is a passive IR camera. In the past, many organizations have assessed the efficiency of this technique of detection and reported widely fluctuating results. It is believed that the main reason for these fluctuations is associated with the ad hoc interpretations used by different researchers. In this paper, a more systematic analysis is presented which takes into account variables such as time of the day, time of the year, weather conditions, type of road and many others. A working model is proposed in order to facilitate the prediction of the JR signature of the buried land-mines and is compared with data acquired from multiple trials. These trials were done with live mines (without fuzes) and surrogates buried in different types of road (packed gravel and sand) and during different times of the day and different times of the year.Jn the last 15 years, with the increase of peacekeeping activities in countries decimated by civil wars and other social disorders, the interest for mine detection and clearance has become increasingly important. To support the international effort to solve this critical problem, the Canadian Department of National Defence (DND) has put together a team of experts to design and build a multi-sensor remotely operated mine detection vehicle operating primarily on roads, the Improved Landmine Detection Capability (ILDC). One critical sensor of this vehicle is a passive JR camera. From recent work published by many organizations (RECON/OPTICAL Inc.,"2 Wackenhut Advanced Technology Corp.,3 \VES,4 ERIM,5 LLNL6'7), it is well accepted that JR technology has good capabilities to detect metal-free buried mines. However, one drawback of this technique is its performance dependency on environmental conditions (time of day, time of year, weather conditions, type of road,...). In this document, the author proposes a methodology well adapted to monitor and anticipate the fluctuations in the efficiency of JR technology in detecting buried mines.We will first describe two models (one being a simplified version of the other) which interpret quantitatively the thermal mechanisms involved in the formation of the JR signature of buried mines. Subsequently, the validity of the quantitative parameters identified by these models is tested experimentally during trials designed especially to reproduce real operating scenarios. Throughout the trials, special attention has been given to the evaluation of the limitations associated with the use of these quantitative parameters. Then, the experimental results are O-8794-2146-4/96/$6.OO SPIEVo!. 2765/489 Downloaded From: http://proceedings.spiedigitallibrary.org/ on 06/...