Molecfit: a general tool for telluric absorption correction

Molecfit is a general tool to correct for telluric absorption lines based on synthetic modelling of the Earth's atmospheric transmission. It combines a publicly available radiative transfer code, a molecular line database, atmospheric profiles, and various kernels to model the instrument line spread function. As a result, the standard deviation of the residuals after correction of unsaturated telluric lines is frequently better than 2% of the continuum. In this presentation, I will briefly describe the tool and the current developments: (a) integration within the ESO pipelines, (b) various improvements, (c) deployment of radiometers at Paranal for precise measurements of the atmospheric temperature and humidity profiles. In particular, in some specific conditions, molecfit is able to blindly correct telluric lines to a high accuracy.