Laser Doppler anemometer instrument for optical noseboom applications

Abstract

We present our ongoing and planned work on a compact, modular laser Doppler anemometer (LDA) serving as an optical air data sensor to measure true airspeed, angle of attack and angle of sideslip. The LDA method utilizes Doppler-shifted backscattering from aerosols within the surrounding air masses, enabling contactless measurements and flush integration with the aircraft fuselage. The instrument builds upon experience gained from a previous flight campaign on the DLR Falcon 20 research aircraft. The new design is intended for flight testing in 2026 and 2027, complemented by parallel in-situ characterization of aerosol size distribution relevant to the sensor's performance. We report on the current status of the new instrument, including laboratory performance and initial characterization results. The system comprises two primary components: first, an Air Transport Rack (ATR)-based laser unit housing the laser source, thermal management, data acquisition, processing systems and data storage; second, an optical head mounted externally on the aircraft fuselage, which projects laser light outward and captures backscattered radiation. These components are interconnected via optical fibers and electrical connections. We emphasize key differences between the current design and the prior proof-of-concept, illustrating an architectural approach suited for future implementation of this sensor as an optical air data system. Finally, an overview of planned flight campaigns and potential future adaptations of the system as an optical noseboom for various aircraft platforms is provided.