NASA plots methane-detecting laser in SPAAACE

Measuring the other greenhouse gas

NASA is working on a laser-based instrument it hopes will be able to take flight to measure atmospheric concentrations of important greenhouse gas methane.

The work is being led by Goddard Space Flight Center scientist Haris Riris, who collaborated with Jim Abshire of Goddard in developing the CO2 Sounder Lidar (light detection and ranging) that gathers round-the-clock carbon-dioxide measurements.

Goddard's media release says the Methane Sounder will follow the same principles, and the agency hopes that like the CO2 sounder it will eventually be deployed on a satellite.

NASA is funding the development ahead of planned flight tests aboard a DC-8 later this year, and if all goes well the agency hopes an instrument could be included aboard a mission like the Active Sensing of CO2 Emissions over Nights, Days and Seasons (ASCENDS).

The release notes that while CO2 is the world's major greenhouse gas, methane is more potent, and scientists expect that methane releases from permafrost will create a feedback mechanism, accelerating warming further.

Riris' project aims to create 24-hour global coverage of methane measurement, something current generations of satellites lack.

Riris is quoted in the release as saying: “This effort would be a continuation and an augmentation to the Franco-German MERLIN (Methane Remote Sensing Lidar Mission) that is currently being formulated.

“The expectation is that our Methane Sounder would have better sensitivity and precision than MERLIN because of the more sensitive detector and the multi-wavelength approach being employed.”

Current detectors are passive devices, whereas the Methane Sounder will carry its own light source, a tunable laser looking at the 1.65 micron band; absorption of that light will provide the measurement of atmospheric methane concentration.

That wavelength is one of the challenges of building a methane-detecting Lidar: to get a 1.65 micron laser beam, Riris needs to combine two wavelengths in a crystal. ®

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