Open AccessA portable miniaturized laser heterodyne radiometer (mini-LHR) for remote measurements of column CH4 and CO2
Author(s) -
E. L. Wilson,
A. DiGregorio,
Gerónimo Villanueva,
C. Grunberg,
Z. Souders,
Karla Miletti,
Arsenio Menendez,
Marc Grunberg,
Melissa Floyd,
J. E. Bleacher,
Eugénie Euskirchen,
C. Edgar,
Bryan J. Caldwell,
B. Shiro,
Kim Binsted
Publication year - 2019
Publication title -
applied physics. b, lasers and optics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.591
H-Index - 131
eISSN - 1432-0649
pISSN - 0946-2171
DOI - 10.1007/s00340-019-7315-8
Subject(s) - radiometer , laser , remote sensing , optics , heterodyne (poetry) , materials science , absorption (acoustics) , lidar , altimeter , environmental science , microwave , heterodyne detection , physics , computer science , telecommunications , geology , acoustics
We present the design of a portable version of our miniaturized laser heterodyne radiometer (mini-LHR) that simultaneously measures methane (CH 4 ) and carbon dioxide (CO 2 ) in the atmospheric column. The mini-LHR fits on a backpack frame, operates autonomously, and requires no infrastructure because it is powered by batteries charged by a folding 30 W solar panel. Similar to our earlier instruments, the mini-LHR is a passive laser heterodyne radiometer that operates by collecting sunlight that has undergone absorption by CH 4 and CO 2 . Within the mini-LHR, sunlight is mixed with light from a distributive feedback (DFB) laser centered at approximately 1.64 μm where both gases have absorption features. The laser scans across these absorption features roughly every minute and the resulting beat signal is collected in the radio frequency (RF). Scans are averaged into half hour and hour data products and analyzed using the Planetary Spectrum Generator (PSG) retrieval to extract column mole fractions. Instrument performance is demonstrated through two deployments at significantly different sites in interior Alaska and Hawaii. The resolving power ( λ /∆ λ ) is greater than 500,000 at 1.64 μm with precisions of better than 20 ppb and 1 ppm for CH 4 and CO 2 , respectively. Because mini-LHR instruments are portable and can be co-located, they can be used to characterize bias between larger, stationary, column observing instruments. In addition, mini-LHRs can be deployed quickly to respond to transient events such as methane leaks or can be used for field studies targeting geographical regions.