Mounted inside a satellite high above the Earth, a powerful fiber-optic laser system, no larger than a laptop computer, fires an ultraviolet beam toward the planet. The beam strikes gas molecules such as ozone, sulfur and carbon dioxide, then bounces back to the satellite, carrying critical information about the health of the atmosphere.
Within five to seven years, this cutting-edge tool, envisioned by engineers at Johns Hopkins and NASA's Goddard Space Flight Center, could be in orbit, gathering important data for scientists who monitor air pollution and atmospheric changes that may be associated with global warming.
NASA recently awarded an $815,500 three-year grant to a Johns Hopkins-Goddard team that plans to design and build a prototype of this device. Jin Kang, an assistant professor in the Hopkins Department of Electrical and Computer Engineering, will create the ultraviolet light source based on fiber-optic laser technology. Engineers at Goddard will fabricate a sturdy housing that will protect the system from the rigors of space travel.
"This kind of laser is ideal for space applications, where it has to be able to survive the rocket vibrations and remain operating in space for a long time," Kang says. "In a fiber-optic laser, the light keeps going around a loop of fibers and gets amplified as it does. It's very simple, and you don't have to align mirrors the way you do with a conventional laser. A fiber-optic laser is very light and highly efficient."
Kang's colleagues at Goddard say these characteristics are important. "We're going to integrate Kang's basic laser into our equipment, making the parts rugged enough to survive space travel and miniaturizing some parts to reduce the size and weight," says Harry Shaw, associate branch head for component technology and radiation effects at Goddard. "We're going to develop a device that is compact, reliable and weighs much less than conventional lasers. That's very attractive to spacecraft designers because it's expensive to put things in space."
The Hopkins-Goddard proposal was one of about a dozen selected from hundreds of proposals NASA received this year in response to a request prepared by the agency's Earth Science Technology Office. Researchers in this office want to foster development of lasers that can be used for atmospheric sensing applications.
This laser device promises to become the critical component of a LIDAR system, a variation of radar that uses light instead of radio waves. In this system, light beams are aimed at the atmosphere. When the beams strike gas molecules, they bounce back, carrying a wavelength absorption "fingerprint" containing information about the identity of gases in the atmosphere and their density. The system could be used, for example, to measure changes in the protective ozone layer that surrounds the Earth.
The engineers from Johns Hopkins and Goddard hope to finish building their fiber-optic laser device within three years. Afterward, the same team hopes to incorporate the laser into a larger research instrument that could be launched into space a few years later.