How aiming at blind telluric line correction can make spectrographs monitoring tools for greenhouse gases

Correction of telluric absorption lines is important during the data reduction of spectroscopic observations of astronomical targets. The popular tool molecfit creates synthetic telluric transmission spectra based on the LBLRTM radiative transfer code, the HITRAN database, available atmospheric profiles (temperature, humidity, pressure variation with altitude), and instrumental line spread functions. Significantly improved accuracy is reached by using atmospheric profiles obtained at the same time and location as the science observations. Provided some conditions are met, the addition of a radiometer providing temperature and humidity profiles every few minutes as well as regular twilight spectra of telluric stars processed by molecfit to measure the atmospheric abundance of a few molecules allow blind telluric line correction, i.e., one can provide the transmission spectrum of the atmosphere for each observation. As a by-product, spectrographs in Chilean observatories can become one of the rare monitoring tools of the abundance of greenhouse gases in South America.