Autonomous multi-species environmental gas sensing using drone-based Fourier-transform infrared spectroscopy

Unmanned aerial vehicles (UAVs) – or drones – present compelling new opportunities for airborne gas sensing, in applications such as environmental monitoring, hazardous scene assessment and facilities’ inspection. Instrumenting a UAV for this purpose encounters trade-offs between sensor size, weight, power and performance, driving the adoption of lightweight electrochemical and photo-ionisation detectors, but at the expense of speed, selectivity, sensitivity, accuracy, resolution and traceability. Here, we report the design and integration of a broadband Fourier-transform infrared spectrometer with an autonomous UAV, providing ro-vibrational spectroscopy throughout the molecular fingerprint region from 3 – 11 µm (3333 – 909 cm-1) and enabling rapid, quantitative aerial surveys of multiple species simultaneously with an estimated noise-limited performance of 18 ppm (propane). Bayesian interpolation of the acquired gas concentrations is shown to provide both localization of a point source with approximately one metre accuracy, and distribution mapping of a gas cloud, with accompanying uncertainty quantification.