ARTS (Atmospheric Radiative Transfer Simulator) is a widely used[2] atmospheric radiative transfer simulator for infrared, microwave, and sub-millimeter wavelengths.

[4] It is designed from basic physical principles and has been used in a wide range of situations.

[7] Absorption is calculated line-by-line, with continua[8] or using a lookup table.

[9] The user programs ARTS by the means of a simple scripting language.

ARTS has been used at the University of Maryland to assess radiosonde humidity measurements,[10] by the University of Bern for water vapour retrievals,[11] by the Norwegian University of Science and Technology for Carbon monoxide retrievals above Antarctica,[12] and by the Japanese space agency JAXA to aid the development of retrievals from JEM/SMILES,[13] among others.