Abstract

During the past three years. Rayleigh-scatter lidar observations have been carried out at Utah State University with a small receiving telescope and a powerful Nd:YAG laser (Wickwar et al, 1995). The combination provided a power-aperture product of 3.4 W.m^–2 at 532 nm for vertical determinations of the temperature structure between 40 and 90 km. A greatly improved lidar facility is currently under development at this mid-latitude site (41.7 N, 111.8 W, 1.5 km) in the middle of the Rocky Mountains. The major elements consist of a fully steerable, large-aperture telescope (based on four specially designed, 1.27-m minors), two solid stale lasers — a powerful, seeded, Nd:YAG laser operating at 532 nm, as before, and an extremely stable, seeded, alexandrite ring laser tunable between 700 and 810 nm—and modem spectral analysis and signal detection systems. Combining the new pointing capability with a power-aperture product greater than 85 W.m^–2, the Nd:YAG laser will be used to determine density, temperature, and wind velocity between 10 and 90 km. A combination of power observations from Rayleigh scatter and spectral observations from both Rayleigh and Mie scatter will be used. Our collaboration with Light Age, Inc., has led to the development of a very stable, spectrally narrow, alexandrite ring laser. By using various combinations of direct emission, Raman shifting, and frequency doubling, resonance-scatter observations can be made from most of the elements, e.g., Na, K, Ca⁺, Al, Mg, Fe, etc. deposited in the atmosphere between 80 and 110 km by meteoric decay. Furthermore, by precisely stepping the emission from the laser system over the backscatter cross section of one of these elements, the resultant spectral observations can be used to determine the temperature and wind velocity in this altitude region. This upgraded CASS lidar facility will thus provide extensive, high time-resolution observations throughout the middle atmosphere from 10 to 110 km, from the troposphere into the lower thermosphere.

© 1996 IEEE