Low Power Greenhouse Gas Sensors for Unmanned Aerial Vehicles
Miller, David J.
Zondlo, Mark A.
Harrison, William A.
Lary, David J.
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We demonstrate compact, low power, lightweight laser-based sensors for measuring trace gas species in the atmosphere designed specifically for electronic unmanned aerial vehicle (UAV) platforms. The sensors utilize non-intrusive optical sensing techniques to measure atmospheric greenhouse gas concentrations with unprecedented vertical and horizontal resolution (similar to 1 m) within the planetary boundary layer. The sensors are developed to measure greenhouse gas species including carbon dioxide, water vapor and methane in the atmosphere. Key innovations are the coupling of very low power vertical cavity surface emitting lasers (VCSELs) to low power drive electronics and sensitive multi-harmonic wavelength modulation spectroscopic techniques. The overall mass of each sensor is between 1-2 kg including batteries and each one consumes less than 2 W of electrical power. In the initial field testing, the sensors flew successfully onboard a T-Rex Align 700E robotic helicopter and showed a precision of 1% or less for all three trace gas species. The sensors are battery operated and capable of fully automated operation for long periods of time in diverse sensing environments. Laser-based trace gas sensors for UAVs allow for high spatial mapping of local greenhouse gas concentrations in the atmospheric boundary layer where land/atmosphere fluxes occur. The high-precision sensors, coupled to the ease-of-deployment and cost effectiveness of UAVs, provide unprecedented measurement capabilities that are not possible with existing satellite-based and suborbital aircraft platforms.
"This work was sponsored in part by the National Science Foundation’s MIRTHE Engineering Research Center (NSF EEC-0540832), NSF SECO ERC/IIP through a subcontract with Bridger Photonics, Inc. (NSF IIP-1038825), and the Office of the Dean of Research at Princeton University. DJM acknowledges support of a NSF Graduate Research Fellowship and L.T. acknowledges support through a generous contribution by Lynn and Thomas Ou. We thank the University of Texas at Dallas for the funds to purchase and operate the remote control helicopters. We thank E. Bou-Zeid, M.L. Baeck, and J.A. Smith for help in arranging the CO2 intercomparison. We thank three anonymous reviewers for their efforts to strengthen and clarify the manuscript."