  We present EOS, a procedure for determining the Outgoing Longwave Radiation
(OLR) and top-of-atmosphere (TOA) albedo for a wide range of conditions
expected to be present in the atmospheres of rocky planets with temperate
conditions. EOS is based on HELIOS and HELIOS-K, which are novel and publicly
available atmospheric radiative transfer (RT) codes optimized for fast
calculations with GPU processors. These codes were originally developed for the
study of giant planets. In this paper we present an adaptation for applications
to terrestrial-type, habitable planets, adding specific physical recipes for
the gas opacity and vertical structure of the atmosphere. To test the
reliability of the procedure we assessed the impact of changing line opacity
profile, continuum opacity model, atmospheric lapse rate and tropopause
position prescriptions on the OLR and the TOA albedo. The results obtained with
EOS are in line with those of other RT codes running on traditional CPU
processors, while being at least one order of magnitude faster. The adoption of
OLR and TOA albedo data generated with EOS in a zonal and seasonal climate
model correctly reproduce the fluxes of the present-day Earth measured by the
CERES spacecraft. The results of this study disclose the possibility to
incorporate fast RT calculations in climate models aimed at characterizing the
atmospheres of habitable exoplanets.
