High Altitude Test Flights of the TWiLiTE Direct Detection Doppler Lidar

In this paper we will present results from a series of test flights of the TWiLiTE (Tropospheric Wind Lidar Technology Experiment) direct detection Doppler wind lidar instrument on the NASA ER-2 research aircraft. The initial engineering flight test program was performed at the Dryden Flight Research Center in Palmdale, California in February, 2011. After extensive modifications additional flights are planned in October, 2012. TWiLiTE measures vertical wind profiles by transmitting an ultraviolet (355 nm) laser pulse into the atmosphere, collecting the laser light scattered back to the lidar reciever by air molecules and measuring the Doppler shifted frequency of the laser return using a double-edge Fabry Perot etalon receiver. The TWiLiTE instrument was developed with support from the NASA Earth Science Technology Office (ESTO) Instrument Incubator Program (IIP). We will briefly describe the instrument with an emphasis on new technologies such as the rotating holographic optical element scanning telescope, the single frequency uv laser and the molecular double-edge Doppler receiver. Example results from the ER-2 test flights will be discussed, including full resolution (1 second temporal resolution; 30 m range resolution) backscatter signal profiles and line-of–sight wind profiles (10 second integration; 250 m range resolution) measured from the ER-2 flight altitude of 20 km. Finally we will discuss future plans to reconfigure TWiLiTE to fly on the NASA Global Hawk as part of the Hurricane and Severe Storm Sentinel (HS3) NASA Earth Venture (EV-1) Mission.