Cavity Ring-Down Methane Sensor for Small Unmanned Aerial Systems.

Area of Science:

• Environmental Science
• Analytical Chemistry
• Aerospace Engineering

Background:

• Methane emissions monitoring is crucial for natural gas infrastructure.
• Existing methods for methane detection may lack portability or sensitivity for sUAS deployment.
• Open-path sensing offers advantages in size and power consumption for aerial applications.

Purpose of the Study:

• To develop and test an open-path cavity ring-down spectroscopy (CRDS) methane sensor for integration with small unmanned aerial systems (sUAS).
• To evaluate the sensor's performance, including sensitivity and precision, under actual flight conditions.
• To demonstrate the utility of the sUAS-mounted sensor for detecting and quantifying methane emissions.

Main Methods:

• Development of a low-mass (4 kg), low-power (12 W) open-path CRDS instrument utilizing a 1651 nm laser and a high-finesse cavity.
• Integration and flight testing of the CRDS sensor on a DJI Matrice 600 hexacopter sUAS.
• Calibration and validation using a controlled release setup to simulate point-source methane emissions.

Main Results:

• The CRDS sensor demonstrated high sensitivity, achieving methane detection precision of approximately 10-30 ppb under flight conditions.
• Successful detection of methane plumes from simulated point sources with mass flow rates as low as ~0.005 g/s.
• The instrument's low mass and power requirements facilitate seamless integration with sUAS (<25 kg all-up mass).

Conclusions:

• The developed open-path CRDS sensor is the first of its kind deployed directly onboard an sUAS.
• The sUAS-based methane detection system offers a valuable tool for emissions monitoring and quantification in the natural gas sector.
• This technology enables more efficient and targeted assessment of methane leaks from infrastructure.