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.

The case for a multi-channel polarization sensitive LIDAR for investigation of insolation-driven ices and atmospheres

“…In order to take advantage of the tremendous research and development that has gone into lasers and fiber optic components that operate in the near-IR by the telecommunications industry in recent years, the instrument will operate at wavelengths between 1.52 and 1.59 μm. These wavelengths are ideally suited to discriminate CO 2 and H 2 O ices and vapor using the differential absorption lidar (DIAL) technique originally developed for terrestrial remote sensing [26,27].…”

“…i.) conduct a sensitive global (daytime and nighttime) search for outbursts of Martian methane down to 2ppb with relative errors of 0.5% [26,27].…”

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).…”

Pump tunable mirrorless OPO: an innovative concept for future space IPDA emitters

“…However, despite the improvement in gas concentration measurement capability and accuracy expected from a spaceborne IPDA Lidar 7,8 , core missions based on this method such as the German-French MERLIN (Methane Remote Sensing Lidar Mission) 9 , are scarce. This is partly due to the technical challenges to be overcome for a free-space high power parametric source to meet the optical, thermo-mechanical, and lifetime requirements imposed by the measurement principle and the operational environment for the instrument [10][11][12][13] More specifically, critical characteristics such as beam propagation quality, pointing stability, and emitted wavelength tunability and accuracy, are directly related to the optical geometry and the alignment tolerances of the different components, which generally leads to rather complex designs, assembly, and control protocols, especially when multiple resonators are involved 11,[14][15][16][17] . In the present study, we introduce an original "mirrorless" (i.e.…”