Lidar to Track Earth Atmosphere

Michael D. Wheeler

Within the next five to seven years, NASA scientists and engineers from Johns Hopkins University plan to launch a next-generation fiber optic laser system to monitor the Earth's atmosphere.

Scientists rely predominantly on weather balloons and radar to gather information about pollution and ozone levels. Researchers have found these methods effective only in providing general information, however.

In the proposed space-based lidar system, a satellite will target the atmosphere with lasers and collect the reflected light. By analyzing the light for wavelength absorption signals specific to various gases, scientists will be able to determine their prevalence in the atmosphere.

The primary components of the system are Q-switched fiber lasers and nonlinear elements, including LiNbO₃, said Jin Kang, an assistant professor of electrical and computer engineering. The 1-W laser will have a wavelength of 310 to 325 nm.

Waveguides will carry the light through the system, eliminating bulk optics and alignments, Kang said. This will make the system lightweight, efficient and reliable -- ideal for operation in orbit, where it must not only survive the stress of launch, but also function with little assistance for the life of the project.

The researchers must demonstrate a working prototype in three years. Engineers at NASA's Goddard Space Center in Greenbelt, Md., are designing the protective housing for the laser. The two groups will coordinate their efforts to produce a complete instrument for launch after the prototype is working.