Emily Wilson
NASA Goddard Space Flight Center, USA
Title: A portable laser heterodyne radiometer for measurements of CH4 and CO2 in the atmospheric column
Biography
Biography: Emily Wilson
Abstract
Laser heterodyne radiometry is a technique based on radio receiver technology that has been in use since the 1970s for measuring trace gases in the atmosphere such as ozone, water vapor, methane, ammonia, and chlorine monoxide. Earlier iterations of this technique featured large, high-powered lasers that limited widespread use and the potential for commericalization. With the relatively recent availability of distributive feedback (DFB) lasers, it has become possible to make this technique low-cost, low-power, and portable. The miniaturized laser heterodyne radiometer (mini-LHR) is a passive variation of this technology developed at NASA Goddard Space Flight Center that measures methane (CH4) and carbon dioxide (CO2) in the atmospheric column by mixing sunlight and DFB laser light in the infrared. The entire instrument fits on a backpack and operates on a fold-out 35 watt solar panel. Over the course of its development, the mini-LHR has been field tested in a range of locations and conditions including urban locations in Washington, DC and Los Angeles, a high-altitude site at Mauna Loa observatory in Hawaii, a rural location in upper Wisconsin, and a dairy farm in California. Recently, the mini-LHR was used to monitor CH4 and CO2 over varying thawing permafrost terrains. In the image, the mini-LHR (right) is shown in a collapse scar bog next to an eddy flux tower (left) at a field site near Fairbanks, Alaska. The mini-LHR operates in tandem with AERONET - a global network of more than 500 sensors that measure aerosol optical depth. The benefit of this partnership is that the mini-LHR could be readily deployed into this global network and provide validation for satellite missions as well as a long-term stand alone data product.
1.Wilson E L et al. (2017) A 4 U laser heterodyne radiometer for methane (CH4) and carbon dioxide (CO2) measurements from an occultation-viewing CubeSat, Measurement Science and Technology 28: 035902.
2.Melroy H R et al. (2015) Autonomous field measurements of CO2 in the atmospheric column with the miniaturized laser heterodyne radiometer (Mini‑LHR). Applied Physics B 120: 609-615.
3.Wilson E L et al. (2014) Miniaturized laser heterodyne radiometer for measurements of CO2 in the atmospheric column. Applied Physics B: Lasers & Optics 114, 385-393, doi:10.1007/s00340-013-5531-1.
4.Clarke G B, Wilson E L, Miller J H, Melroy H R (2014) Uncertainty analysis for the miniaturized laser heterodyne radiometer (mini-LHR). Measurement Science and Technology 25: 055204-055209.
5.Sinclair J A, Irwin P G J, Calcutt S B Calcutt, Wilson E L (2015) On the detectability of trace chemical species in the martian atmosphere using gas correlation filter radiometry.