Assessment of Pulsed Lidar Measurements of Aircraft Wakes Using a Lidar Simulator: Vortex Position Estimates for IGE, Linking, and Oblique Viewing, and Dependence of Vortex Lifetime on SNR

Abstract

4NorthWest Research Associates, Inc., Redmond, WA, 98052 A lidar simulator tool was developed to simulate realistic raw lidar signal data generated from a wake vortex velocity field as measured by the existing Lockheed Martin Coherent Technologies (LMCT) WindTracer � pulsed lidar, currently used in the field to measure aircraft wake vortices. The raw lidar data is processed and the resulting product files are input into the existing LMCT Wake Vortex Processing Algorithm to estimate position and circulation strength versus wake age. The estimates from the Wake Vortex Processing Algorithm are then compared to truth data used to generate the raw lidar signal data. Accuracy of the Wake Vortex Processing Algorithm estimates of lateral and vertical position is evaluated by exercising the lidar simulator using input wake vortex fields based on analytical vortex models and 3-D Large Eddy Simulation computations for two aircraft types under IGE, OGE linking, and oblique viewing conditions. This study shows that the mean biases of the vortex position estimates for IGE and OGE linking vortices are small and similar to those for non-linking vortices in the OGE region reported in an earlier study 1 . The use of the lidar at oblique angles relative to the trailing line vortices does not introduce significant differences in the position biases. An analysis of the vortex lifetime estimates with SNR variations suggests avoiding lidar measurements for SNRs below 0 dB.