Ultra-Lightweight Mid-IR Methane Sensor for UAV-based Measurements

Abstract. We developed an ultra-lightweight mid-infrared laser spectroscopic sensor for precise, rapid mobile measurements of atmospheric methane concentrations aboard small uncrewed aerial vehicles. The design is simple and compact, featuring a Herriott-type multi-pass cell in an open-path configuration. A single board computer with two on-chip microprocessor units allows rapid data acquisition and onboard wavelength modulation spectroscopy, making the sensor a stand-alone turnkey instrument. Including the dedicated battery, the sensor weighs 1.2 kg and consumes up to 11 W of electrical power under standard laboratory conditions making it one of the most lightweight sensors reported. The measurement resolution is 3.7 ppb at a 1 s averaging time. We deployed the sensor in controlled-release experiments and detected methane flux rates as low as 0.2 kg h^-1. Consequently, it can be deployed to measure fugitive emissions from anthropogenic and natural sources that would be undetectable for other methods.