Effelsberg Radio Telescope
View Point, Picnic Area
Europe Germany
The Effelsberg 100-metre Radio Telescope is a radio telescope in the Ahr Hills (part of the Eifel) in Bad Münstereifel, Germany. Inaugurated in 1972, for 29 years the Effelsberg Radio Telescope was the largest fully steerable radio telescope on Earth, surpassing the Lovell Telescope in the UK. In 2000, it was surpassed by the Green Bank Observatory's Robert C. Byrd Green Bank Telescope in Green Bank, US, which has a slightly larger elliptical 100-by-110-metre (330 by 360 ft) aperture.
The Effelsberg radio telescope is operated by the Max Planck Institute for Radio Astronomy in Bonn, the radio astronomy institute of the Max-Planck-Gesellschaft. It was constructed from 1968 to 1971 and inaugurated on 1 August 1972. A major technical difficulty in building a radio telescope of 100 m diameter was how to deal with the deformation of the mirror due to gravity when it is rotated to point in a different direction. The mirror must have a precise parabolic shape to focus the radio waves, but a conventionally-designed dish of this size would sag slightly when rotated so the mirror loses its parabolic shape. The Effelsberg telescope uses a novel computer-designed mirror support structure which deforms in such a way that the deformed mirror will always take a parabolic shape. The focus will move during such deformation, and the feed antenna suspended in front of the mirror is moved slightly by the computer control system as the telescope is rotated to keep it at the focus. Tests after completion of the telescope showed that the intended accuracy of the mirror surface of 1 mm had not only been met, but exceeded significantly.