These are two lidar trailers behind Building 21 at Goddard Space Flight Center. You can see the bright green laser light coming out of the roof of one of the trailers. Measurements are made at night; otherwise, sunlight would overwhelm the small signal of laser light scattered back to the instrumentation in the trailers.
Lidar is an acronym standing for Light Detection and Ranging. It is the direct, optical analog to Radar, which uses radio waves. In a typical Lidar experiment, laser light is transmitted into the atmosphere. The beam can interact with the atmosphere in a number of different ways;
Laser light that has been scattered in any of these ways can then be detected using a telescope and light sensitive detectors. Add some electronics to acquire and store the signals from the detectors, and you have a typical Lidar instrument. Distance of the scattering molecules or particles from the transmission site can be deduced if a pulsed laser is used; one simply measures the time from the laser pulse to the time that the Lidar signal is received. Instruments using these various scattering mechanisms have been designed and built within Code 916.
Back to the Ground-based and Airborne Instruments page
Last Updated: 1997-01-14
Web Curator: lrlait (Hughes STX) (email@example.com)
Responsible NASA organization/official: Dr. P. K. Bhartia, Atmospheric Chemistry and Dynamics Branch/Head