Title of Presentation: Compact and Rugged Transceiver for Coherent Doppler Wind Lidar Applications in Space

Primary (Corresponding) Author: Michael J. Kavaya

Organization of Primary Author: NASA Langley Research Center

Co-Authors: Grady J. Koch, Jirong Yu, Farzin Amzajerdian, Upendra N. Singh, Bo. C. Trieu, Ed. A. Modlin, Mulugeta Petros, Yingxin Bai, Karl Reithmaier, Paul J. Petzar

Abstract: High-accuracy, vertical profiles of the horizontal vector wind in earth’s atmosphere, with the global coverage of an orbiting sensor, are the most highly desired measurement of NASA’s Science Mission Directorate Weather Focus Area and of the unmet measurements of the tri-agency (DOD, NOAA, NASA) National Polar-orbiting Operational Environmental Satellite Systems (NPOESS) Integrated Program Office (IPO). They are also wanted by NOAA, DOD, EPA, DHS, and many other countries. The wind measurement was one of the fifteen NASA earth science missions recently recommended by the NRC Earth Science Decadal Survey (DS), getting top ranking from the NRC DS Weather Science and Applications Panel, and high ranking from the Water Resources and Global Hydrologic Cycle Panel. The DS stated that wind measurements will help the following urgent societal benefit areas: Extreme Event Warnings, Human Health, Improved Weather Prediction, and Air Quality. Other publications indicate that the wind measurements will help Climate Prediction since the same physical models are used both for weather forecasting and climate prediction. After many years of Doppler lidar theoretical development, computer simulation, experimental technology validation, and space mission instrument and design; coupled with Observing System Simulation Experiments (OSSEs) to determine wind measurement requirements; it is the consensus of NASA and NOAA that the most cost effective, lowest risk measurement method with the earliest achievable mission date is the hybrid Doppler lidar method which utilizes both coherent- and direct-detection Doppler lidars to obtain the desired profiles. Since the coherent Doppler lidar works best at the lower altitudes where there are the highest aerosol levels, and the direct Doppler lidar works best at the higher altitudes where the atmospheric extinction is lowest, the combination of both is very complementary. The preferred laser wavelength for the coherent portion of the hybrid Doppler lidar is approximately 2 microns. NASA Langley Research Center (LaRC) has advanced the 2-micron pulsed solid-state laser greatly over the past 15 years and is now the world leader in high energy, 2-micron lasers. LaRC has now demonstrated 1.2 J of pulse energy whereas the requirement for a 400-km hybrid Doppler lidar mission is only 0.25 J. The IIP project reported here is an effort to increase the ruggedness and to compactly package the LaRC state-of-the-art laser technology. Each step of this effort is being performed with future aircraft validation flights and eventual space qualification in mind.