Frequency Modulation Spectroscopy Modeling for Remote Chemical Detection

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Frequency modulation (FM) spectroscopy techniques show promise for active infrared remote chemical sensing. FM spectroscopy techniques have reduced sensitivity to optical and electronic noise, and are relatively immune to the effects of various electronic and mechanical drifts. FM systems are responsive to sharp spectral features and can therefore reduce the effects of spectral clutter due to interfering chemicals in the plume or in the atmosphere. The relatively high modulation frequencies used for FM also reduces the effects of albedo (reflectance) and plume variations. Conventional differential absorption lidar (DIAL) systems are performance limited by the noise induced by speckle. Analysis presented ... continued below

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Sheen, David M. September 30, 2000.

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Frequency modulation (FM) spectroscopy techniques show promise for active infrared remote chemical sensing. FM spectroscopy techniques have reduced sensitivity to optical and electronic noise, and are relatively immune to the effects of various electronic and mechanical drifts. FM systems are responsive to sharp spectral features and can therefore reduce the effects of spectral clutter due to interfering chemicals in the plume or in the atmosphere. The relatively high modulation frequencies used for FM also reduces the effects of albedo (reflectance) and plume variations. Conventional differential absorption lidar (DIAL) systems are performance limited by the noise induced by speckle. Analysis presented in this report shows that FM based sensors may reduce the effects of speckle by one to two orders of magnitude. This can result in reduced dwell times and faster area searches, as well as reducing various forms of spatial clutter. FM systems will require a laser system that is continuously tunable at relatively high frequencies (0.1 to 20 MHz). One promising candidate is the quantum-cascade (QC) laser [1, 2]. The QC laser is potentially capable of power levels on the order of 1 Watt and frequency tuning on the order of 3 - 6 GHz, which is the performance level required for FM spectroscopy based remote sensing. In this report we describe a high-level numerical model for an FM spectroscopy based remote sensing system, and application to two unmanned airborne vehicle (UAV) scenarios. A Predator scenario operating at a slant range of 6.5 km with a 10 cm diameter telescope, and a Global Hawk scenario operating at a range of 30 km with a 20 cm diameter telescope, has been assumed to allow estimation of the performance of potential FM systems.

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  • Report No.: PNNL-13324
  • Grant Number: AC05-76RL01830
  • DOI: 10.2172/1023146 | External Link
  • Office of Scientific & Technical Information Report Number: 1023146
  • Archival Resource Key: ark:/67531/metadc843268

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Office of Scientific & Technical Information Technical Reports

Reports, articles and other documents harvested from the Office of Scientific and Technical Information.

Office of Scientific and Technical Information (OSTI) is the Department of Energy (DOE) office that collects, preserves, and disseminates DOE-sponsored research and development (R&D) results that are the outcomes of R&D projects or other funded activities at DOE labs and facilities nationwide and grantees at universities and other institutions.

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  • September 30, 2000

Added to The UNT Digital Library

  • May 19, 2016, 3:16 p.m.

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  • Nov. 28, 2016, 6:05 p.m.

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Sheen, David M. Frequency Modulation Spectroscopy Modeling for Remote Chemical Detection, report, September 30, 2000; Richland, Washington. (digital.library.unt.edu/ark:/67531/metadc843268/: accessed December 18, 2017), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.