RASTA, Radiometer for Automatic Stations

In order to improve the understanding of the atmosphere in general and of the radiation ßeld in particular, routine direct radiation measurements represent a powerful tool to monitor changes of the atmospheric transparency, ibr example due to an increase of the aerosol load. All-weather automatic measuring devices are needed for that purpose. The RASTA Systems, consisting of a sun-trackef, an absolute radiometer and up to three sunphotometers, have been deveioped in the recent years within ajoint venture between a research institute, two private companies and a governmental institution. A complete description of the Systems and preliminary results are presented, especially conceming the effects of the aerosol cloud injected in the stratosphere by the Pinatubo volcanic eruption in 1991.