Green beam to receive upgrade
Utah State University’s 18-watt laser – the Green Beam – will upgrade this summer to allow for more accuracy and increased capability.
The Green Beam, which extends from the roof of the Science Engineering Research Building, has been used since 1993 to measure the temperature of Earth’s middle atmosphere. For example, its data supports the concept that the atmosphere is warmer in the winter than in the summer.
Josh Herron, a graduate student studying physics, helps run the laser. He said monitoring temperature changes over time, aids the study of global warming.
The $160,000 laser, funded by the National Science Foundation and the U.S. Air Force, uses a system of mirrors and a telescope to transmit light and direct the path of the beam. The beam pulses as it stretches into the atmosphere.
“The human eye blends [the pulsing] together to create one long beam,” Herron said.
The new system will add a four-watt red beam, which will alternate pulses with the green one. The red beam will probably not be visible, though, he said.
The new beam will measure wind speeds and temperatures using potassium ions remaining in the atmosphere from meteors. While the current system can extend 45 to 90 kilometers into Earth’s atmosphere, the new system will reach up to 120 kilometers, Herron said.
Along with the new beam will come a new telescope for capturing light. It will be made of four 50-inch mirrors and will have 30 times the collecting power of the current 17-inch telescope for taking measurements, he said.
“What would usually take all night will take 24 minutes,” Herron said.
Vincent Wickwar, the physics professor who supervises the Green Beam, said the lidar (like radar, only with light instead of radio waves) system can see fine details in time evolution and altitude that a satellite cannot. Combination of data from the Green Beam with that from satellites will lead to a better understanding of the atmosphere, he said.
Herron said the new system will be computer-controlled. Right now, six undergraduate students take turns operating the beam through the night. They can turn it off if anything goes wrong, although that is unlikely, he said.
The eight-millimeter beam could permanently blind someone if it came in contact with his or her eyes. But, it would only burn the surface of a hand that touches it, he said. The beam sparkles when viewed close-up because of its interaction with dust particles.
“It is an important experiment with respect to Cache Valley because it is so visible,” he said.
“At least a couple hundred” people tour the Green Beam each year, he said. It helps spark interest in young children to learn more about science.
The beam can only be run on clear nights. That translates to about 80 nights or 1,000 hours of the year, Wickwar said.
USU has one of about 12 lidar facilities in the world. After the new system is implemented, USU will have one of three facilities (aside from those owned by the military) in the world that test temperature and metal ions simultaneously, he said.
The University of Western Ontario in Canada has such a facility as does Alomar in Northern Norway. Each facility makes its own contribution. Alomar tests the atmosphere at a latitude different from the one at which USU and Ontario test. However, the Ontario facility is different from USU’s in that it tests sodium levels in the atmosphere instead of potassium, Wickwar said.
Herron said, “All the stuff we do gets put into a big pool of common knowledge.”
The Green Beam gives graduate and undergraduate students alike the opportunity to take part in filling that pool of knowledge. The new system set to operate this summer will make their research even more influential. Wickwar said he hopes for the best.