NASA’s Langley Research Center has developed an algorithm, Airborne Wind Profiling Algorithm for Doppler Wind Lidar (APOLO), that offers highly accurate, real-time measurement of wind parameters (i.e., direction and speed) by airborne wind lidar sensors. APOLO enables the extraction of accurate wind speed and direction from noisy flight environments, and provides correction for instrument installation biases. The algorithm has been incorporated into a supporting software package that displays accurate airborne Doppler wind lidar data, and offers several data post-processing and display functionalities. The offset compensation and parameter extraction technology could be used in a variety of applications where the motion and orientation of a lidar sensor may result in data inaccuracy. NASA is seeking licensees that may benefit from integration of the compensation algorithm and data post-processing software into existing or developing systems.
APOLO and its supporting data processing package were developed for NASA’s Doppler Aerosol Wind (DAWN) lidar to compile three-dimensional wind profiles for improved hurricane forecasting models. The data acquisition and processing software displays wind profile parameters that include Doppler shift, power distribution, wind direction, and wind velocity. Doppler shift created by aircraft motion is measured by the internal navigation and GPS system, and is fed to a signal processing system that utilizes APOLO for real-time removal of aircraft effects from wind measurements. APOLO also corrects instrument offsets that arise from GPS/INS unit misalignment, lidar telescope misalignment, and scanner installation bias. Offset compensation routines, based on the minimum mean square error principle, estimate offset angles using ground-return lidar data to compensate for their adverse effect to wind parameter estimation. APOLO utilizes two perpendicular lines-of-sight Doppler shift observations, compensation for aircraft motion along each line of site, then a vector sum to determine wind parameters.
The technology has been utilized in a flight environment, and wind vectors have been measured from altitudes as high as 10 km. Plots of wind speed data produced by the lidar data analysis package are provided in the figure. Similar plots of wind direction as a function of altitude are also generated from the lidar measurements.
This technology has applications in the following areas: clear air turbulence and aircraft wake detection systems for aircraft safety, 3D wind mapping for offshore turbine placement optimization and economic analysis, upward-looking buoy-mounted lidar for offshore turbine placement optimization and economic analysis, study of weather and wind patterns in meteorology, aircraft-mounted imaging and mapping lidar for aerial geographic surveys, and shipborne mapping and navigation lidar for oceanographic surveys.