Wind Mapping with Doppler Lidar Using a New Approach for Increased Measurement Range*

Within recent years, the emerging advanced air mobility (AAM) industry has been growing rapidly with an increase in the number of uncrewed aircraft system (UAS) operations and new urban air mobility concepts on the horizon. To integrate AAM into the National Airspace System, new micro-weather measurements and forecasts will be required as current weather observations and forecasts are generally too sparse to capture weather conditions impactful to AAM. Given the low wind tolerances and limited battery reserves of many small UAS in confluence with the complex environments these aircraft fly within (e.g., urban areas, at low-altitudes, around complex terrain, etc.), high-resolution accurate wind information in particular is of paramount importance to facilitate safe and efficient UAS flights. Anemometers near the surface are of limited utility to AAM particularly around take-off and landing locations, but are inadequate alone in complex environments as they are often not representative of a wide area and provide little information about winds above the ground at flight level.

Doppler lidar is a prime wind sensor candidate to fill in this measurement gap, as it is able to survey the winds over a wide area detecting variations in the wind flow volumetrically with an appropriate scanning strategy. Using dual-Doppler approaches from multiple systems, both the wind speed and direction can be directly measured. However, a main limitation of Doppler lidar is its limited range, which is typically around five kilometers or less for many commercially available systems, highly dependent on aerosol loading and other conditions. To mitigate this range limitation, MIT Lincoln Laboratory has developed a new approach to conduct dual-Doppler analysis using Doppler spectra instead of radial velocity measurements from multiple lidars to take wind measurements at a lower signal-to-noise ratio, effectively increasing the lidar range. This new methodology will be presented, along with verification statistics with sonic anemometer measurements and an example of how the technique can be used to map the winds over an area in comparison to the traditional dual-Doppler method.

* DISTRIBUTION STATEMENT A. Approved for public release. Distribution is unlimited.

This material is based upon work supported by the Department of the Air Force under Air Force Contract No. FA8702-15-D-0001. Any opinions, findings, conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the Department of the Air Force.