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High Accuracy Trace Gas Measurements from a Lightweight UAV

Article/Figure Provided By: Colm Sweeney and Pieter Tans

Recently, numerous studies have contested the global impact of fugitive emissions from oil and gas operations on the methane budget.  Consequently, precise quantification of gas leaks is needed to better constrain the total methane burden from this source.  In the past, high precision insitu analyzers mounted in a research aircraft have been used to circle the suspected leak and quantify the plume.  While this is a robust method, it is costly, and missions cannot be deployed quickly.  Quick deployment is needed because leaks can be transient, variable, and a huge safety hazard.  A lightweight UAV is uniquely suited to both fly through a plume generated by a leak, and deploy quickly at little cost. However, the UAV platform is too small to carry the 70-pound analysis system used on a plane.

NOAA GMD has developed a unique sampling system, called the Active AirCore, in which a pump compresses air into a 100-meter long, small diameter tube at a constant flow rate. This long tube acts as an “atmospheric tape recorder” by storing the sample stream in the long tube. When the sample is analyzed, the data is a “play back” of the air the UAV flew through while in flight.  The sampler can be removed from the UAV, and immediately analyzed using an ultra-high precision trace gas analyzer like those used on aircraft.  This new sampling system provides the same level of accuracy as an analyzer mounted on a larger aircraft, but is light enough to be flown on a UAV.  Because the measurements are done in a van at the flight location, data analysis and quantification of the leak is near-real time.  This near-real-time analysis allows highly flammable natural gas leaks to be quickly identified and quantified providing information that will help evaluate the safety and potential economic losses at an individual oil and gas production site.

Fig 1. Active AirCore payload on simulated gas leak detection flight, December 2018.