Single photon Lidar gas imagers for practical and widespread continuous methane monitoring (original) (raw)
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The challenges of measuring methane from space with a LIDAR
CEAS Space Journal
The global and regional quantification of methane fluxes and identification of its sources and sinks has been highlighted as one of the goals of the NASA 2017 Earth Science Decadal Survey. Detecting methane from space and airborne platforms with an active (laser) remote sensing instrument presents several unique technology and measurement challenges. The instrument must have a single frequency, narrow-linewidth light source, and photon-sensitive detector at the right spectral region to make continuous measurements from orbit, day and night, all seasons and at all latitudes. It must have a high signal to noise ratio and must be relatively immune to biases from aerosol/cloud scattering, spectroscopic and meteorological data uncertainties, and instrument systematic errors. At Goddard Space Flight Center (GSFC), in collaboration with industry, we have developed an airborne instrument to measure methane. Our instrument is a nadir-viewing lidar that uses Integrated Path Differential Absorption (IPDA), to measure methane near 1.65 µm. We sample the absorption line using multiple wavelengths from a narrow linewidth laser source and a sensitive photodetector. This measurement approach provides maximum information content about the CH4 column, and minimizes biases in the XCH4 retrieval. In this paper, we will review our progress to date and discuss the technology challenges, options and tradeoffs to measure methane from space and airborne platforms.
Lidar-based gas analyzer for remote sensing of atmospheric methane
arXiv (Cornell University), 2024
Enhancement of methane emission measurement techniques is necessary to address the need for greenhouse gas emissions monitoring. Here we introduce a gas analyzer designed for remote sensing of atmospheric methane aboard unmanned aerial vehicles. This device employs the wavelength modulation spectroscopy approach and quadrature detection of laser radiation scattered from the underlying surface. Our results demonstrate that the observed correlation between various signal attributes and the distance to the surface, where laser radiation scatters, aligns with analytical expectations. Calibrations proved that the instrument provides reliable methane measurements up to 120 meters while being lightweight and power efficient. Notably, this device outperforms its competitors at altitudes exceeding 50 meters, which is safer for piloting.
Journal of Applied Remote Sensing
We report on an airborne demonstration of atmospheric methane (CH 4) measurements with an integrated path differential absorption lidar using an optical parametric amplifier and optical parametric oscillator laser transmitter and sensitive avalanche photodiode detector. The lidar measures the atmospheric CH 4 absorption at multiple, discrete wavelengths near 1650.96 nm. The instrument was deployed in the fall of 2015, aboard NASA's DC-8 airborne laboratory along with an in situ spectrometer and measured CH 4 over a wide range of surfaces and atmospheric conditions from altitudes of 2 to 13 km. We will show the results from our flights, compare the performance of the two laser transmitters, and identify areas of improvement for the lidar. © The Authors. Published by SPIE under a Creative Commons Attribution 3.0 Unported License. Distribution or reproduction of this work in whole or in part requires full attribution of the original publication, including its DOI.
Differential Absorption Lidar at 1.67 µm for Remote Sensing of Methane Leakage
Japanese Journal of Applied Physics, 1999
A differential absorption lidar (DIAL) for field monitoring of methane (CH4) leakage at a wavelength of 1.67 µm was developed. Compared with traditional DIAL systems for environmental monitoring, this system has a higher distance resolution (∼15 m) for determining the leak position and a shorter detection range up to 500 m. First, considering appropriate design parameters, a theoretical simulation was performed to evaluate the sensitivity and the detectable range of the system. Based on the analytical simulation, a prototype DIAL system was constructed and the detection of CH4 which had leaked into the atmosphere was demonstrated. The CH4 leakage of 6000 ppm·m at a distance of 130 m was successfully detected. The detection limit was 1000 ppm·m. With the improvements in the light source and the detector system, the detectable boundary can be increased in the range from 90 to 540 m for a concentration of 1500 ppm·m.