The world's second largest radio telescope utilizes five cable carriers to reliably supply two receiver cabins with electrical power, cooling water and control information, as well as transfer test data. The telescope's frequencies range between 800 MHz and 86 gHz and is used by scientists all over the world to discover pulsars and quasars, neutron stars, black holes and supernova explosions. The priority for those charged with making the telescope run smoothly is safe media and data supply.
The Effelsberg radio telescope is located in Effelsberg, Germany. The Max-Planck-Institute for Radio Astronomy (MPIfR) in Bonn, Germany operates this “huge dish” which allows astronomers to look into the most distant corners in space to discover pulsars and quasars (active galaxies), neutron stars, black holes and supernovae explosions. The telescope is used by scientists all over the world including Canada, China, Russia, Japan, South America, South Africa and numerous countries in Europe.
The radio telescope's primary mirror has a diameter of 100m and is accompanied by a 6.5m secondary mirror. The telescope has a total weight of approximately 3,200 tons and rotates on a 64m circular (azimuth) track diameter. Signals received are guided into two receiver cabins, one 30m above the mirror directly in its primary focal point and the other in the focus of the secondary mirror located in the center of the primary mirror.
When tilting the mirror, the control system moves 1,800 tons with the precision of a millionth of a full circle (360 degrees) and achieves accuracy below 1 arc sec. The primary mirror can be tilted between seven and 94 degrees, with a default setting at 90 degrees. Engineers installed cable carrier systems at the connecting surface of the telescope's concrete foundation and its parabolic reflector to supply the receiver cabins with electrical power, control data, cooling water and to send back measurement data. The original design used an open style, super-duty stainless-steel carrier system manufactured by KabelSchlepp America Inc.
The telescope is currently being reworked and expanded. Operators are installing a new receiver system in the primary mirror, requiring considerably more data cables. Plus, the telescope is being fitted with a new secondary mirror with each segment being rotated separately to balance out remaining gravity-related errors of the primary mirror and further increase the resolution of the telescope.
To achieve these goals, new power and control cables need to be installed and design engineers are adding two new cable carriers to the telescope system. The specific carrier type, KabelSchlepp's SX 1250, offers a system length of more than 6.6m, an overall width of 780 mm and a bending radius of 500 mm.
“We are calculating a life expectancy of 25 to 30 years. The old KabelSchlepp cable carrier fulfilled this requirement and we expect the same service life from the new chain, as well,” says Klaus Bruns, the radio telescope's operating mechanical engineer. Engineers selected a stainless-steel design, versus plastic, to guarantee mechanic robustness, since the primary mirror's extreme position exposes the chain to severe stress.
A main stress on the carrier is temperature fluctuations: winter temperatures as low as -30C and summer temperatures up to 38C. The new carriers are designed to protect the cables and hoses against UV radiation, which led to selection of a totally enclosed stainless-steel system.
Rainer Sachert, an electrical engineer on the project, also sees an advantage in the carrier's load capacity. The carrier is designed for an applied load of 50 kg per meter. But at present the carrier is only partially filled with an actual additional load of approximately 15 kg and, once all cables and hoses are installed, the additional load of the carrier will be nearly 20 kg per meter.
This means a high safety reserve from a premature failure. The partially filled carrier has 10 cables with each 24 LWL cores, 16 special HF cables with extremely constant damping, as well as six special cables for the power supply of the new sub-reflector. Even though the original cable carrier supplied 25 years ago still performs well, the new cable carriers are more durable using an optimized carrier link design and improved stroke system.