ATSTEP (Germany, Forschungszentrum Karlsruhe) is a Gaussian puff model for diagnosis and prognosis of the atmospheric dispersion, deposition, gamma radiation and doses of released radioactivity in case of accidents in nuclear power plants or during transport, and from dirty bombs. It is designed for running in the RODOS (Real-time On-line DecisiOn Support) system for nuclear emergency management. RODOS is operational at the German Federal Office for Radiation Protection (BfS), and test operational in many European countries. Information on RODOS you find at [[1]]. Information on ATSTEP you find here.