Wednesday, August 27, 2014                

Contact Us

For more information about these technologies and services, please contact:

Dr. Gary Gimmestad, Ph.D., Team Lead

LIDAR and Active EO Systems
Phone: 404-407-6029
Fax: 404-407-9029

Electro-Optical Systems Laboratory
Georgia Tech Research Institute
925 Dalney St.

Atlanta, GA 30332-0834

Lidar Projects

20 Years of Lidar at GTRI


In 1987, GTRI researchers developed their first lidar - an unattended lidar system for cloud climatology studies.  We developed  the first 1.54 micron eye safe lidar for clouds and aerosols in 1989. This tradition of innovation continues to day, with research like the RPOT and ALE lidar projects.


CCFU: First Unattended Eye-safe Lidar


The Cloud Climatology Field Unit (CCFU) was the first unattended eye-safe lidar. The system was designed to acquire vertical lidar soundings at regular intervals for months at a time with little operator intervention and minimal maintenance requirements. The lidar was capable of detecting heavy cloud decks such as stratocumulous at medium altitudes, but it was not capable of detecting high, thin cirrus. The system operated for several weeks in April 1987. During this time, it was evaluated for reliability, lidar sensitivity, and maintenance requirements. The software performed flawlessly, and the system was truly autonomous.


MegaLidar: World's Largest Lidar


The GTRI lidar group developed the largest lidar facility in the world at the time (1988). MegaLidar used a lidar system based on the 100-inch optical collimator at Wright Patterson Air Force Base in Dayton, OH, which  was developed for middle atmosphere studies. In a series of measurements in December 1988, the system was demonstrated by recording Rayleigh backscatter returns from mesospheric air molecules at altitudes from 40 to 90 km. These returns were then used to develop atmospheric density profiles in the middle atmosphere, with a time resolution on the order of minutes and a spatial resolution of about 1 km. The Megalidar facility was operated by researchers from the Air Force Geophysics Laboratory at Hanscom Air Force Base for several years following the demonstration described here.

1.5 Micron Lidar for Clouds and Aerosols


GTRI developed a 1.54 micron eye-safe lidar for clouds and aerosols in 1989. The lidar was later modified and operated in support of an intensive set of air chemistry measurements in Atlanta, GA, which were part of the Southern Oxidants Research Program (SORP) during the summer of 1992. The original version of the lidar produced the first reported measurements of atmospheric backscatter up to 11 km at 1.54 microns.



ECIPS: International Network of Lidars and Radiometers


The Experimental Cloud Lidar Pilot Study (ECLIPS) was initiated to obtain statistics on cloud-base height, extinction, optical depth, cloud brokenness, and surface fluxes. Two observational phases took place, in October-December 1989 and April-July 1991, with intensive 30-day periods within the two time intervals. Data have been archived at NASA Langley Research Center and are available to the international scientific community.


During the course of this research, GTRI developed the first thermal infrared all-sky camera. One useful feature of cloud images obtained by the all-sky camera is that they provide a measure of both cloud brokenness and amount, and cloud optical depth variations, the latter from the variable cloud brightness.


Starfire Optical Range Lidar for Subvisual Cirrus Detection


The lidar's purpose was to monitor patchy subvisual cirrus clouds and changes in boundary layer aerosols to find the cause of variations in the extinction of light as it passed through the atmosphere (at right, photo courtesy of US Air Force).


The primary use of the lidar was to monitor patchy subvisual cirrus clouds but was developed to monitor all atmospheric particulates, including boundary layer aerosols. This condition necessitated two receiver channels - a long-range telescope with a six-inch diameter and a short-range telescope with a two-inch diameter. The SOR lidar system was in routine use for several years, until the CVL guide star was de-commissioned.



Smoke Lidar


In 1994, GTRI developed and tested a compact, light-weight lidar system that was installed and operated on a 275-foot tower. The lidar was designed to have sufficient temporal and spatial resolution to map out the internal structures of smoke clouds as they drifted over a target on the ground, as well as a data recording system with enough speed and capacity to acquire the resulting data. The lidar was used to characterize two different kinds of smoke.


 The lidar system performed as expected during the smoke tests. No significant problems were encountered. The resulting data were used to guide the development of a fractal model for smoke clouds.

NEXLASER: Unattended Ozone Lidar


The overall purpose of the NEXLASER project is to provide air quality modelers and air chemists with the key information that they need in order to understand ground-level ozone concentrations in urban environments. The detailed information provided by NEXLASER will enable better air quality forecasts as well as better strategies for improving air quality. The goal of the NEXLASER project is to develop and commercialize unattended lidar systems for continuously monitoring vertical profiles of ozone and aerosols in polluted urban environments.



EARL: Lidar Education Initiative


This project began in Sept 2001, when Agnes Scott College and the Georgia Institute of Technology were awarded a grant from the National Science Foundation to jointly develop an eye safe atmospheric lidar. Agnes Scott College constructed a new, dedicated laboratory for the lidar instrument using design specifications provided by Georgia Tech.


The main objective of the joint project is to provide a unique hands-on research experience for undergraduates, including undergraduate women. Students from both institutions construct the lidar under the supervision of Agnes Scott and Georgia Tech faculty members, and they operate it routinely over a period of several years.


Many scientific questions can be addressed with lidar, but boundary layer studies are especially relevant in Atlanta as they relate to air quality. For example, light lidar backscatter by boundary layer aerosols is correlated with visibility, which is an important measure of air quality. The aerosols can also be used as tracers, to measure the thickness of the mixing layer, which is a key parameter in air quality models.


The proposed lidar instrument and undergraduate research program are intended to serve as national models for other educational institutions. (For further information about having your educational institution become a part of the lidar research program, please email Gary Gimmestad.)

RPOT: Range Profiles of Turbulence


The RPOT lidar provides aerosol and turbulence profiles along the optical path to a ground target. RPOT uses the turbulence profile to calculate the expected beam spreading, beam wander, and formation of hot spots. The lidar uses the aerosol profile for extinction calculations. The slant path occurs at the same elevation angle as the kill laser beam. A compact version of the turbulence lidar installed on a tracking mount has been deployed at HELSTF. Learn more here.



ALE: Astronomical Lidar for Extinction


GTRI and the University of New Mexico developed a rugged lidar to be used for measuring atmospheric extinction in support of the CCD/Transit Instrument. The Astronomical Lidar for Extinction (ALE) is eye-safe, capable of pointing in any direction, and built for unattended operation in an observatory environment. ALE provides real-time continuous monitoring, and real-time measurements of the amount of atmospheric extinction as well as the cause, ie low-lying aerosols, dust or smoke in the free troposphere, or high cirrus. In addition, ALE detects the altitude of aerosols, from which their type can be inferred, giving us an idea of their wavelength dependence. Learn more here.





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