© 2005 OSA/OSHS 2005
P15
REAL: High-power, eye-safe, scanning lidar for aerosol cloud detection and tracking Shane D. Mayor and Scott M. Spuler National Center for Atmospheric Research, P.O. Box 3000, Boulder, Colorado 80307-3000
[email protected] and
[email protected]
Abstract: The Raman-shifted Eye-safe Aerosol Lidar (REAL) is well-suited for detection and tracking of otherwise invisible aerosol clouds in urban areas. © 2005 Optical Society of America OCIS codes: (140.3550) Lasers, Raman; (280.3640) Lidar
1.
Introduction
Just as weather radars map the location of precipitation, lidars (laser radars) can locate and track plumes of aerosol particulate matter that would otherwise be invisible to the human eye. During the last few years, we have developed a new lidar that enables unprecedented high-resolution imagery of aerosol plumes and atmospheric structure. This breakthrough in active remote sensing comes from the ability to reliably generate high-energy laser pulses at 1.5 microns wavelength with sufficiently low divergence that commercial-off-the-shelf photodetectors can be used in the receiver. The 1.5-1.8 micron wavelength region is highly desirable to operate in because it offers the highest eye-safety of anywhere in the optical spectrum. By operating within this band, a laser can transmit higher pulse energy than other wavelengths and remain eye-safe. This band also features other advantages for an aerosol lidar such as invisibility, transparency, low sky-background, and low molecular scattering. 2.
Depolarization
In addition to the ability to detect and track relatively low-concentration aerosol plumes, we have also developed backscatter depolarization sensitivity for REAL. This capability allows us to infer aerosol particle shape. Spherical particles return the laser light in the same polarization plane as the transmitted beam. Non-spherical particles return varying amounts of laser light in other polarization planes. The depolarization technique has been practiced for many years. By implementing it on REAL, we can now extend the capability to investigations of think aerosol clouds near the surface of the earth. 3.
Instrument Availability
The prototype REAL (called “v1”) with depolarization capability is owned and operated by the National Center for Atmospheric Research’s Earth Observing Laboratory which is funded by the National Science Foundation. Requests for use of the instrument may be submitted to the director of the laboratory. A second version of REAL (called “v2”) is designed for continuous and unattended use and has been created by ITT Industries via a technology transfer agreement with NCAR. 4.
References
[1] Mayor, S. D., S. M. Spuler, and B. M. Morley, 2005: Scanning eye-safe depolarization lidar at 1.54 microns and potential usefulness in bioaerosol plume detection. SPIE Lidar Remote Sensing for Environmental Monitoring IV, Paper 5887-23, San Diego, CA. [2] Spuler, S. M. and S. D. Mayor, 2005: Scanning Eye-safe Elastic Backscatter Lidar at 1.54 microns, J. Atmos. Ocean. Technol., 22, 696-703. [3] Mayor, S. D. and S. M. Spuler, 2004: Raman-shifted Eye-safe Aerosol Lidar, Appl. Optics, 43, 39153924.
