Title: A Methane Lidar for Greenhouse Gas Measurements
Presenting Author: Haris Riris
Organization: NASA GSFC
Co-Author(s): Kenji Numata, Stewart Wu, Brayler Gonzalez, Mike Rodriguez, Fahey Molly, Anthony Yu, Mark Stephen, Stephen Kawa, Jianping Mao, William Hasselbrack, Martha Dawsey, Stan Scott

Abstract:
Atmospheric methane (CH4) is the second most important anthropogenic greenhouse gas with a much higher radiative forcing of carbon dioxide (CO2). CH4 also contributes to pollution in the lower atmosphere through chemical reactions leading to ozone production. At Goddard Space Flight Center (GSFC) we have been developing the technology needed to remotely measure CH4 from orbit, using lasers. Our concept for a CH4 lidar is a nadir viewing instrument that uses the strong laser echoes from the Earth's surface to measure CH4. The instrument has a tunable, narrow-frequency light source and photon-sensitive detector to make continuous measurements from orbit, in sunlight and darkness, at all latitudes and can be relatively immune to errors introduced by scattering from clouds and aerosols. Our measurement technique uses Integrated Path Differential Absorption (IPDA), which measures the absorption of laser pulses by a trace gas when tuned to a wavelength coincident with an absorption line. We will present results from an airborne demonstration using a lidar at 1.65 um using two different laser architectures based on optical parametric generation.