The challenges of measuring methane from space with a lidar

Abstract

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.

Quantifying methane emissions from the global scale down to point sources using satellite observations of atmospheric methane

“…It can observe over water and at night, but its sensitivity and coverage are lower than for the solar backscatter instruments. Lidar capability to observe methane from space is currently limited by laser technology (Riris et al, 2019).…”

Orbiting and In-Situ Lidars for Earth and Planetary Applications

“…The multi-wavelength measurement approach minimizes biases in the CH4 retrievals. [40] Understanding the reactive photochemistry of Formaldehyde (HCHO) allows us to learn about the lifetime of greenhouse gases like methane, the production of ozone, and the growth of secondary organic aerosols which is critical to NASA's Earth Science goals. As part of the Instrument Incubator Program (IIP) funded by the Earth Science Technology Office (ESTO), we are developing a laser system that will make this measurement by employing a new method to detect formaldehyde remotely with integrated path differential absorption (IPDA) lidar [41,42].…”

Next-Generation Digital Ecosystem for Climate Data Mining and Knowledge Discovery: A Review of Digital Data Collection Technologies

“…Available ground-based measurements of these pollutants are sparse and limited in their global representation (Frankenberg et al, 2005 ). Existing CH 4 monitoring networks are considered inadequate to explain observed trends and variation in atmospheric CH 4 (Riris et al, 2019 ). Advances in EO technology have the potential to enhance measurement accuracy for these gases in particular, which primarily result from natural (e.g., wetlands, ruminant animals, rice cultivation) and anthropogenic sources (e.g., fossil fuels; Frankenberg et al, 2005 ).…”

“…Advances in EO technology have the potential to enhance measurement accuracy for these gases in particular, which primarily result from natural (e.g., wetlands, ruminant animals, rice cultivation) and anthropogenic sources (e.g., fossil fuels; Frankenberg et al, 2005 ). While a handful of satellites have existed since the mid-1990s for remotely measuring CH 4 from space, they have primarily been used for detecting hotspots or evaluating emission trends rather than for use in developing emissions inventories, which requires a greater sensitivity to constrain to a more local level, although EO-derived CH 4 measurements have so far been evaluated to be fairly accurate and show promise for climate policy applications (Jacob et al, 2016 ; Riris et al, 2019 ). Governments are planning to deepen EO capabilities for GHG monitoring, including NASA, which is designing the Geostationary Carbon Observatory (GeoCARB) system that will provide as many as 10 million daily observations to measure methane plumes near the earth's surface (Fialka, 2018 ).…”