Affiliation:  Max-Planck-Institut für Radioastronomie, Bonn, Germany

Title:  The Effelsberg 100-m radio telescope: 40 years of radio astronomy

Time: 3:30pm, (Friday) November 4, 2011

Location:　Middle Conference Room, 3rd floor

Abstract:

The decision to construct a 100-m fully steerable radio telescope in Germany, capable of operations even at 1-cm wavelength was taken in 1964. Three steel companies were asked to design at first an 80-m dish with high precision surface. It was obvious at that stage that a heavy, solid construction could not meet the set specifications. Instead the idea was followed that the steel construction could be flexible but during tipping in elevation a parabolic surface would be maintained by steel elasticity. The Krupp steel company submitted a design that allowed for absolute deflections of 80-mm in the support structure but a parabolic surface would be maintained with ~ 1-mm r.m.s.. Only the focal point, where the receivers were placed, would have to be steered to meet the changing parabola surfaces. Computations suggested that these specifications would be met even for a 100-m dish, which was in fact constructed.

Many details went into the design and the construction of the 100-m radio telescope. The foundations were started in 1968. The supporting steel structure was made in the Krupp company works and delivered by road in 1969. The dish construction was made on site by the MAN company that also assembled the telescope. The drives were a joint project of the AEG Telefunken (electric drives) and Ferranti (computer steering). The programmes for the astronomical movements were an in-house project of the Max-Planck-Institute. Also the cables and receivers were an in-house MPI design. The telescope was completed in 1971 and had an official opening on 12th May 1971. Regular astronomical observations started in June 1972 after numerous optimization procedures were completed.

The 40 years of operations needed continuous maintenance but also allowed for improvements. The telescope must be painted in a 10-year rhythm to prevent corrosion. The drives need regular maintenance. Some of the panels had to be replaced: the inner 60-m surface due to failure of honeycomb glued panels and the outer 80 to 100-m rings due to corrosion of the steel mesh. The primary and secondary focus cabins were redesigned to optimise the use with many receivers. The track failed several times, usually at welds due to fatigue failure. One complete replacement of the rail track was made. Also the 6.5-m Gregorian sub-reflector was replaced twice, the most recent replacement was with a unit that has actuator-controlled surface. This improvement allows the telescope to be used even at 3-mm wavelength. The 100-m radio telescope is in a very good condition, capable of best research in radio astronomy over a very wide frequency band.