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  skos:definition """The Aerosol Research Branch (ARB) Light Detection and Ranging (LIDAR) project has been taking ground based LIDAR measurements from Langley Research Center in Hampton, Virginia since May 1974.  These LIDAR measurements provide high resolution vertical profiles of the upper tropospheric and stratospheric aerosols. The LIDAR system has evolved over the years and provides a valuable long-term history of the middle-latitude stratospheric aerosol.

Project Description:
The measurements for ARB were made using a LIDAR system.  This system uses a ruby laser that emits one joule per pulse with a repeat rate of 0.15 hertz (Hz) at a wavelength of 0.6943 micrometers.  This system also uses a 48 inch cassegrainian configured telescope mounted on a movable platform.  The transmitter laser beam has a divergence of about 1.0 mrad, and the maximum receiver field of view is 4.0 mrad. The LIDAR has a signal bandwidth of 1 MHz, and this is equal to a 150 meter vertical resolution.  Three photomultiplier tubes are used to enhance the dynamic range.  These tubes are electronically switched on at specific times after the laser has been fired.  The photomultiplier tube output signals are processed by 12-bit Computer Automated Measurement and Control (CAMAC) based digitizers and acquired by a personal computer.

Data Used and Produced:
The Aerosol Research Branch (ARB) 48-inch LIDAR (ARB_48_IN_LIDAR) data set contains data collected from a 48-inch LIDAR system located at NASA Langley Research Center.  Each granule consists of one year of data.  Data are available from 1982 through the present.  Data are continuously being collected.  The days of data are different in each granule.  Each measurement consists of four parameters: stratospheric integrated backscatter from tropopause to 30 km, altitude levels, scattering ratio at each altitude level, and aerosol backscattering coefficient at each altitude level.  An image has been produced to represent the data collected for each granule.

Project Archive Contact:  Langley DAAC User Services Office
                                Mail Stop 157D
                                NASA Langley Research Center
                                Hampton, VA 23681-0001
                                USA
                                Phone: (757) 864-8656
                                Email: support-asdc@earthdata.nasa.gov
                                WWW:  http://eosweb.larc.nasa.gov/

      Project Manager Contact:  M. Patrick McCormick
                                Physics Department
                                Hampton University
                                Hampton, VA  23668
                                USA
                                Phone: (757) 728-6867
                                Email: pat.mccormick@hamptonu.edu
                                Mary T. Osborn
                                SAIC
                                Atmospheric Science Division - Aerosol
      Research Branch
                                Mail Stop 475
                                NASA Langley Research Center
                                Hampton, VA  23681-0001
                                USA

      References:
      Fuller, W. H., Osborn, M. T., and Hunt, W. H. 48-Inch Lidar Aerosol
      Measurements Taken at the Langley Research Center - May 1974 to December 1987. 
      NASA RP-1209, 1988.

      Osborn, M. T., R. J. DeCoursey, C. R., Trepte, D. M. Winker, and
      D. C. Woods, Evolution of the Pinatubo Volcanic Cloud Over Hampton, Virginia,
      Geophys. Res. Lett., Vol. 22, No. 9, May 1, 1995, pp 1101-1104.

      Russell, Philip B., Swissler, Thomas J., and McCormick, M. Patrick,
      Methodology for Error Analysis and Simulation of Lidar Aerosol
      Measurements. Appl. Opt., vol. 18, no. 22, Nov. 15, 1979, pp. 3783-3797.

      Woods, D. C., M. T. Osborn, D., M. Winker, R. J. DeCoursey, and
      O. Youngbluth, 48-inch Lidar Aerosol Measurements Taken at the Langley Research
      Center - July 1991 to December 1992. NASA RP-1334, 1994."""@en ;
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