High-resolution field deployable instrument line shape calibrated-laser heterodyne radiometer for accurate atmospheric methane (CH4) detection

• Development of a high-resolution LHR based on near-infrared laser heterodyne spectroscopy. • Implementation of on-site calibration of ILS for LHR. • The ILS-calibrated LHR is field deployable and more accurate. • The ILS-calibrated LHR performance was verified by remote sensing of atmospheric methane (CH 4 ). The performance of a near-infrared (NIR) high-resolution field deployable instrument line shape (ILS) calibrated-laser heterodyne radiometer (LHR) for accurate measurement of atmospheric CH 4 column abundance is demonstrated. The ILS-calibrated LHR employs a distributed feedback (DFB) laser centered at 1653 nm to extract the CH 4 absorption spectrum information in the atmospheric column from solar radiation. Based on the measured spectra and regularization deconvolution algorithm, the ILS of the LHR is accurately determined. Validation of the retrieved ILS is performed using low-pressure CH 4 gas cell, and the accuracy is improved by 97 % compared to conventional ILS. Compared to traditional LHRs, the ILS-calibrated LHR leads to a 30 % reduction in residuals near the wings of the absorption lines and a 200 % reduction at the peak positions, resulting in a 10 % enhancement in the accuracy of the column abundance determination. The reported field deployable ILS-calibrated LHR provides valuable insights for the accurate measurement of greenhouse gases in Earth’s atmosphere.