Methane gas leak quantification employing infrared sensing at suspected leak sites

We present a conceptual design for an in-situ methane gas sensor that could be deployed rapidly to suspected sites of spurious methane emission. Based on the remote detection of suspected methane leaks now possible with a class of satellites currently in orbit or soon to be launched, in-situ sensors would be deployed to the location of the detection, and accurate measurements of methane leak rates would be reported. Our design is very high level at this time, but incorporates a spectral capability that allows switching on and off the wavelengths of peak methane emission to facilitate detection. Unlike the case for the satellite-based sensing of the gas, our design will lead to the quantification of smallest levels of methane leaks. Two approaches will be considered: ground sensors detecting methane in emission against a cooler sky background, and aerial sensors detecting the gas in absorption against the ground scene as a background source. Sensitivity plays a key role, with the infrared detector working in the 2.4-micron region and operating with near-theoretical sensitivity, with the limiting noise sources set by the background levels for the ground sensor. Consideration of levels of detector dark current, based on the background signal level, and required detector operation temperatures will be derived. The paper reports on the conceptual design, with details on the electronics approach needed to realize the needed levels of sensitivity. Performance quantification will be accomplished through simulation using accurate noise models.