A low-cost miniaturized laser heterodyne radiometer (mini-LHR) for near-IR measurements of CO2 and CH4 in the atmospheric column

The miniaturized laser heterodyne radiometer (mini-LHR) is a ground-based passive variation of a laser heterodyne radiometer that uses sunlight to measure absorption of CO₂ and CH₄ in the infrared. Sunlight is collected using collimation optics mounted to an AERONET sun tracker, modulated with a fiber switch and mixed with infrared laser light in a fast photoreciever. The amplitude of the resultant RF (radio frequency) beat signal correlates with the concentration of the gas in the atmospheric column.