Miniaturized laser heterodyne radiometer for measurements of CO_2 in the atmospheric column

摘要

We nave developed a low-cost, miniaturized laser heterodyne radiometer for highly sensitive measurements of carbon dioxide (CO_2) in the atmospheric column. In this passive design, sunlight that has undergone absorption by CO_2 in the atmosphere is collected and mixed with continuous wave laser light that is step-scanned across the absorption feature centered at 1,573.6 nm. The resulting radio frequency beat signal is collected as a function of laser wavelength, from which the total column mole fraction can be de-convolved. We are expanding this technique to include methane (CH_4) and carbon monoxide (CO), and with minor modifications, this technique can be expanded to include species such as water vapor (H_2O) and nitrous oxide (N_2O).