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Open AccessArticle

Cavity Ring-Down Methane Sensor for Small Unmanned Aerial Systems

1
Department of Mechanical Engineering, Colorado State University, Fort Collins, CO 80525, USA
2
TCB Engineers, Surprise, AZ 85374, USA
*
Author to whom correspondence should be addressed.
Sensors 2020, 20(2), 454; https://doi.org/10.3390/s20020454
Received: 23 December 2019 / Revised: 8 January 2020 / Accepted: 9 January 2020 / Published: 14 January 2020
(This article belongs to the Special Issue Sensors for Unmanned Aircraft Systems and Related Technologies)
We present the development, integration, and testing of an open-path cavity ring-down spectroscopy (CRDS) methane sensor for deployment on small unmanned aerial systems (sUAS). The open-path configuration used here (without pump or flow-cell) enables a low mass (4 kg) and low power (12 W) instrument that can be readily integrated to sUAS, defined here as having all-up mass of <25 kg. The instrument uses a compact telecom style laser at 1651 nm (near-infrared) and a linear 2-mirror high-finesse cavity. We show test results of flying the sensor on a DJI Matrice 600 hexacopter sUAS. The high sensitivity of the CRDS method allows sensitive methane detection with a precision of ~10–30 ppb demonstrated for actual flight conditions. A controlled release setup, where known mass flows are delivered, was used to simulate point-source methane emissions. Examples of methane plume detection from flight tests suggest that isolated plumes from sources with a mass flow as low as ~0.005 g/s can be detected. The sUAS sensor should have utility for emissions monitoring and quantification from natural gas infrastructure. To the best of our knowledge, it is also the first CRDS sensor directly deployed onboard an sUAS. View Full-Text
Keywords: methane; natural gas; oil and gas; landfill; cavity ring-down spectroscopy; spectroscopy; laser absorption; small unmanned aerial system; unmanned aerial vehicle; drone methane; natural gas; oil and gas; landfill; cavity ring-down spectroscopy; spectroscopy; laser absorption; small unmanned aerial system; unmanned aerial vehicle; drone
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Martinez, B.; Miller, T.W.; Yalin, A.P. Cavity Ring-Down Methane Sensor for Small Unmanned Aerial Systems. Sensors 2020, 20, 454.

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