Long-Range Compact Economical Lidar for Wind Profiling

Beyond Photonics is developing a high-performance wind measurement lidar system, which we have named the Wind Beyond lidar, that will enable reliable wind measurements to 20+ km near-horizontal ranges in the atmospheric boundary layer. Use of in-band-pumped Er:YAG laser crystals for the Wind Beyond transmitter allows for much higher pulse energies than are possible with low-cost all-fiber transmitter architectures. The proposed Wind Beyond lidar will operate at 7.5 mJ pulse energy and 1 kHz PRF, resulting in a transmitter figure of merit that is about 10x larger than typical commercially available lidar systems based on Er:fiber transmitters. The significantly lower transmitter PRF than used in most commercial Er:fiber-based lidar systems (typically 10+ kHz) eliminates range ambiguity problems and lowers signal acquisition and processing requirements. The proposed lidar operates at a very-high-transmission wavelength near 1645 nm which also supports the ability to measure winds at long distances. Even with its significantly higher pulse energy, the proposed lidar is a Class 1M eye-safe system. Although the focus of the near-term development is for wind measurement applications, operation near 1645 nm also allows for potential application to atmospheric methane and water vapor concentration measurements in the future. The Wind Beyond lidar transmitter enables: Measurement to near-horizontal-path ranges that are 2-3 times larger (exact factor depending on atmospheric visibility) than possible with the lower performance lidars at equivalent update rates i.e., coverage of much larger measurement volume at a given update rate. Measurements to the same range as the lower performance lidars but with approximately 100x the measurement update rate i.e., coverage of a fixed measurement volume 100x faster. A combination of very small discrete optical components and precision fabrication methods provides an innovation which allows for economical manufacturing. Beyond Photonics recognizes and has years of experience in addressing the hazards of wind events with respect to aviation. Wind events are still responsible for aviation casualties. The capability we present in this program addressed requested requirements with a AAM wind profiling lidar capable of accurately measuring these events well beyond 10 km while providing significant improvements in performance, size, weight, reliability, and cost for eye-safe lidar applications. We have completed proof of concept analysis of a lidar, including transceiver hardware breadboard, of a system capable of achieving 20 to 30 km wind measurements, and resolutions better than 1 m/s of speed, 5 ° of direction, and less than 5 m in vertical altitude increment. Innovations provided are: technical advancement of next-generation lidars, system-level improvements, optimization of high-performance transmitters, and incorporation of novel and modern manufacturing processes supporting performance improvements, cost, and environmental robustness and are critical to the success of coherent wind lidar systems. Phase II primary technical objective is to improve the performance, cost, size, mass, and efficiency of 1.6-micron wavelength based lidar systems by: Utilizing a compact master oscillator and power amplifier configuration so that the required pulse waveforms can be created in a very compact oscillator and then amplified by an efficient compact high-gain amplifier module to the required power / energy levels. Developing a highly compact and robust transceiver module which is small and lightweight, and so rugged that it can withstand outdoor environments and maintain internal alignment permanently without manual or automated adjustment mechanisms. Developing a transceiver fabrication approach that is compatible with automated assembly, aimed at reducing fabrication costs. The key deliverable planned for this program is a high performance compact prototype transceiver unit.
Benefits: NASA applications of the compact Doppler lidar include supporting Advanced Air Mobility (AAM) integration by providing 3D winds over large areas for aviation safety and management. Modified versions of the product will also allow for methane and water vapor measurements which will find application in NASA greenhouse gas concentration and flux measurement systems. The lidar technology can be used from airborne and eventually space-based platforms supporting NASA space-based 3D winds program. The long measurement range wind lidar will have significant application in wind energy and aviation safety. Airborne versions will allow for leak detection along methane gas pipelines. Compact transmitters optimized for heterodyne detection lidar will find use in DoD laser remote sensing applications that involve identifying and tracking hard targets.