A vehicle-mounted dual-comb spectroscopy system developed by researchers in China is capable of measuring methane in real time while traveling on urban roads and expressways.
The instrument maintained stable performance at speeds of up to 100 km/h, detected controlled natural gas releases, and mapped the distribution of a methane plume. The researchers at East China Normal University present it as the first vehicle-mounted mid-infrared dual-comb spectroscopy platform demonstrated under mobile field conditions.
Dual-comb spectroscopy uses two optical frequency combs with slightly different repetition rates to capture broadband, high-resolution molecular spectra rapidly. Operating in the mid-infrared region provides access to strong, distinctive absorption features from many molecules, making the technique well suited to trace-gas analysis. However, the precise optical alignment required can leave laboratory systems vulnerable to vibration and environmental noise.
“Dual-comb spectroscopy uniquely enables simultaneous, high-precision measurement of multiple gases, but is sensitive to environmental noise, which can degrade its performance. Our work addresses and overcomes this key challenge,” said research team leader Wenxue Li in a press release.
During a one-hour, 47 km test in Shanghai, the instrument collected methane and water vapor measurements every second. In separate campus measurements, it achieved precisions of 66 ppb for methane and 114 ppm for water vapor with 10 seconds of averaging.
The team also drove past two controlled natural gas releases positioned beside a road. The system distinguished and located both plumes, recording methane increases of several ppm above background.
“Our system requires no pre-deployed hardware at the field site, maintains near-laboratory-grade detection accuracy while in motion, supports vehicle speeds up to 100 km/h and can geolocate gas plume hotspots,” said co-author Daping Luo.
The researchers now plan to broaden the instrument’s spectral coverage to measure more gases simultaneously, improve long-term baseline stability, and automate the analysis of large mobile datasets. Further miniaturization could also allow the system to be carried by drones for measurements beyond the road network.
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