Jonathan S. Friedman

Cornell University, NAIC Arecibo Observatory, HC-03 Box 53995, Arecibo, PR 00612

High spectral resolution lidars are used for the measurement of winds in the low-to-middle atmosphere. At the Arecibo Observatory, we make Doppler measurements of middle-atmospheric winds using Rayleigh lidar and mesopause temperatures using resonance lidar. Both of these techniques require extremely high spectral resolution, on the order of 1 part in 10^7. In order to achieve and maintain this resolution, we employ molecular and atomic vapor filters.The Rayleigh lidar requires the use of two molecular iodine filters. One is used to frequency lock the injection-seed laser that acts as a master oscillator to force the pulsed laser doubled Nd:YAG transmitter into a single-longitudinal mode. The other is used on the receiver in a differential detection scheme to resolve the Doppler shift.Resonance lidar is a spectral measurement. For this reason an atomic vapor filter is only required for the transmitter. As with the Rayleigh lidar, the filter is used to lock the seed laser, in this case an external cavity diode laser. The power transmitter, in this case a pulsed alexandrite laser, can then do high-spectral resolution measurements of potassium in the mesopause region (80-105 km). The spectral width gives the temperature, which can be measured from about 85-99 km.