Raman Airborne Spectroscopic Lidar

The Raman Airborne Spectroscopic Lidar (RASL) consists of a 15W ultraviolet laser, a 24-inch (61-centimeter) diameter Dahl-Kirkham telescope, a custom receiver package, and a structure to mount these components inside an aircraft. Both the DC-8 at NASA Dryden and the P-3 at NASA/Wallops are aircrafts that could carry RASL. The system is unique because it requires the largest window ever put into either of these aircraft. A fused-silica window, diameter of 27 inches (68.6 centimeters) and 2.375 inches (6 centimeters) thick is needed to withstand the pressure and temperature differentials at a 50,000-foot (15.2-kilometer) altitude.

In June through August of 2007, RASL flew numerous times on board a King Air B-200 aircraft out of Bridgewater, VA, in support of the 2007 Water Vapor Validation Experiments (WAVES) campaign. The WAVES campaign was a series of field experiments to validate satellite measurements. RASL data, along with data from ground-based and balloon-borne instruments, were used to assess the CALIPSO and TES instruments and for studies of mesoscale water vapor variability. During the test flights, RASL produced the first-ever simultaneous measurements of tropospheric water vapor mixing ratio and aerosol extinction from an airborne platform.

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Airborne Raman Ozone, Temperature, and Aerosol Lidar

This is a stratospheric lidar which is configured to fly on the NASA DC-8. It is a zenith viewing instrument, which makes vertical profile measurements of ozone, aerosols and temperature. Stratospheric ozone can be measured at solar zenith angles greater than ~30 degrees, while temperature and aerosols require SZA > 90 degrees. The SNR is maximized under dark coonditions. The measurement of Near-field water vapor measurements is being investigated and could be readily implemented. The instrument utilizes a XeCl excimer laser and a Nd-YAG laser to make DIAL, Raman DIAL, and backscatter measurements. A zenith viewing 16" telescope receives the lidar returns.

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