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Water-Vapor Raman Lidar System Reaches Higher AltitudeA Raman lidar system for measuring the vertical distribution of water vapor in the atmosphere is located at the Table Mountain Facility (TMF) in California. Raman lidar systems for obtaining vertical water-vapor profiles in the troposphere have been in use for some time. The TMF system incorporates a number of improvements over prior such systems that enable extension of the altitude range of measurements through the tropopause into the lower stratosphere. One major obstacle to extension of the altitude range is the fact that the mixing ratio of water vapor in the tropopause and the lower stratosphere is so low that Raman lidar measurements in this region are limited by noise. Therefore, the design of the TMF system incorporates several features intended to maximize the signal-to-noise ratio. These features include (1) the use of 355-nm-wavelength laser pulses having an energy (0.9 J per pulse) that is high relative to the laser-pulse energy levels of prior such systems, (2) a telescope having a large aperture (91 cm in diameter) and a narrow field of view (angular width .0.6 mrad), and (3) narrow-bandpass (wavelength bandwidth 0.6 nm) filters for the water-vapor Raman spectral channels. In addition to the large-aperture telescope, three telescopes having apertures 7.5 cm in diameter are used to collect returns from low altitudes.
Document ID
20100009671
Document Type
Other - NASA Tech Brief
Authors
Leblanc, Thierry (Jet Propulsion Lab., California Inst. of Tech. Pasadena, CA, United States)
McDermid, I. Stewart (Jet Propulsion Lab., California Inst. of Tech. Pasadena, CA, United States)
Date Acquired
August 25, 2013
Publication Date
March 1, 2010
Publication Information
Publication: NASA Tech Briefs, March 2010
Subject Category
Man/System Technology and Life Support
Report/Patent Number
NPO-45007
Distribution Limits
Public
Copyright
Public Use Permitted.

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