Near infrared heterodyne radiometer for continuous measurements of atmospheric CO2 column concentration

We report a laser heterodyne radiometer (LHR) using a distributed feedback (DFB) diode laser operating in the near infrared region as the local oscillator to continuously measure atmospheric carbon dioxide (CO2) column concentration, which has a spectral resolution of 0.09 cm(-1). The measurements for three consecutive days show that the averaged CO(2 )column concentration are 411.5 ppm, 410.4 ppm and 409.5 ppm, respectively. The averaged measurement precision is 1.6% by analyzing the standard deviation of CO2 column concentration. The relative error of 0.3% is estimated by comparing to CO2 average column concentration derived from GOSAT data on October 31, 2018 during the same measurement period. Moreover, the CO2 results are in good agreement with those measured by the ground-based Fourier transform spectrometer (FTS) simultaneously. The results prove the capacity and the reliability of the developed near infrared LHR to monitor the time series of regional CO2.