An Open-Path Tunable Diode Laser Sensor for Simultaneous Measurement of Methane and Carbon Dioxide

D. Michelle Bailey, George Washington University, dmbailey@gwmail.gwu.edu (Presenter)
Erin M. Adkins, George Washington University, webster@gwmail.gwu.edu
Emily L Wilson, NASA GSFC, emily.l.wilson@nasa.gov
J. Houston Miller, George Washington Univ, houston@gwu.edu

Melting arctic permafrost is a large carbon source which releases greenhouse gases (GHG) into the atmosphere. In a collaboration between NASA Goddard Space Flight Center, the University of Alaska-Fairbanks, and the George Washington University a study of the feedbacks to climate change caused by melting permafrost has been initiated. An array of ground experiments at three unique permafrost sites will record permafrost depth, structure, meteorological data, and emissions of key greenhouse gases during a springtime permafrost melt. Ground data will be linked to climate models and landscape structure from satellite imagery to gauge the magnitude of the feedbacks.

GWU will perform high-sensitivity ground-level measurements of carbon dioxide and methane. Currently, we are developing a low-power and portable open-path instrument which builds on our laboratory’s previous experience with deployment of multi-laser, multi-species sensors. Recent work has concentrated on the design and construction of the launch and collection unit which houses collinear visible and NIR laser beam delivery optics and a 2-in diameter, parabolic collection telescope packaged in a less than 0.7-ft³ enclosure. Spectral simulations suggest that at ambient levels of CO₂ and CH₄ (400 and 2 ppmV, respectively) we will observe ≈ 1% absorption over a 200 meter path. Prior work in our laboratory suggests that a signal-to-noise ratio (SNR) in excess of 100 will be achievable at these absorption levels using sweep averaging techniques.

Here we report on the progress of the sensor’s construction with a focus on the design of the field prototype.

Presentation Type:  Poster

Session:  General Contributions   (Tue 4:35 PM)

Associated Project(s): 

• Wilson, Emily: Characterizing Thawing Permafrost Carbon Emissions: An Integrated Pilot Study in Support of Satellite Evaluation/Design and Earth System Modeling Capabilities ...details
• Related Activity: Related Activity or Previously Funded CC&E Activity not listed ...details

Poster Location ID: 98