Update on the Development of Optical Remote Sensing Tools for Quantification of Greenhouse Gases from Distributed Area Sources

Abstract:

Our goal is to develop and validate advanced optical measurement technologies to enable accurate quantification of greenhouse gas (GHG) sources and sinks with a well-characterized uncertainty. Our focus is the measurement of distributed-area sources with spatial scales ranging from of 1 km² to 10 km². A few examples of distributed sources include landfills, mines, gas and oil production sites, carbon sequestration sites, enhanced oil-recovery sites, etc. The goal is to measure both concentration and wind speed of the emitted gas to determine the emission flux.

To achieve our measurement goals we are developing several complementary differential absorption LIDAR (DIAL) systems. The systems are designed for the detection of methane and carbon dioxide, but they vary in the type of laser source, the range resolution, the wavelength tuning method, detector type, and expected use.

A limiting component of DIAL systems in the short wave infrared is detector technology. There are four detectors currently being tested, three single-photon detectors, and one linear-mode, which include an 8 % quantum-efficiency photomultiplier tube, 300 pixel array of Geiger-mode APDs with an effective area of 200 μm, a 100 MHz linear mode APD with a diameter of 500 μm, and a single-pixel Geiger-mode APD gated at 1.25 GHz whose active-area diameter is < 50 μm.

We have also acquired a commercially produced mobile aerosol LIDAR system that has the following measurement capabilities: aerosol to molecular scattering ratio, molecular temperature, density, and line-of-sight wind velocity. The aerosol LIDAR system operates at three wavelengths 1064 nm, 532 nm, and 355 nm. Extinction, backscatter, and depolarization measurements are performed at 532 nm and 1064 nm. The wind velocity and temperature measurements are performed at 355 nm and use direct detection methods. The system is housed in a trailer with scanning capabilities. The presentation will provide an overview of the NIST LIDAR systems, recent results, a discussion of detector technology, and plans for deployment of the DIAL systems.