It's not the Bat Signal -- it's a laser to explore the middle atmosphere
By Emily Jensen
The green laser fires into space over Logan to measure the middle atmosphere. / Photo by the Lidar Observatory
On a clear night, people walking around the campus of Utah State University may notice the green beam shooting straight up from the Science and Engineering Research Building and wonder why USU uses an advertising searchlight.
In truth, they have just been introduced to the Atmospheric Lidar Observatory (ALO), a project begun in 1993 and funded by the National Science Foundation. The lidar (light detection and ranging) is a radar device designed to explore the middle atmosphere, or mesosphere, to gain the data needed to measure absolute temperature. The science, a mixture of physics and chemistry that studies the mesosphere, is called aeronomy.
The lidar mostly consists of a powerful Nd:YAG laser, a 44-centimeter telescope and a sensitive detector for the laser light that returns from the sky.
Dr. Vincent Wickwar, a professor of aeronomy at USU, involved with project, explains, "The laser sends out a powerful pulse of light, a little of which is scattered off dust particles and gas molecules at every altitude. We then use a telescope to collect together the photons that are scattered back towards us. From the measurements at each altitude, we can calculate a profile of the number of molecules."
USU scientists then can graph this profile and determine the slope, which gives them the absolute temperature.
Dr. Wickwar said the project is funded by the National Science Foundation until the middle of 2001. And if the project continues, with the addition of more atmospheric detectors, researchers will be able to measure winds and measure both night and day.
"We will continue as long as we are funded to operate the lidar and conduct scientific investigations with it. We would like to contribute to the study of global warning. To do that, we have to operate for as many years as possible," he said.
Students may go and see the origin of the ALO by contacting the Wickwar, via email at firstname.lastname@example.org. He will put the student in contact with one of the graduate students who nightly run the lidar. For more information or research, one can also visit the ALO site at control.cass.usu.edu/lidar/index.htm.
When Dr. Wickwar was asked what makes the ALO so cool, he responded
with some atmospheric humor, "Are you referring to the observatory or
to the temperatures in the mesosphere near 90-km altitude?"