SCHOTT solutions no. 1/2010 > Astronomy

Manufacturing this complex geometry called for the highest precision possible. ”Nevertheless, in some areas, we were even able to deliver greater accuracy of shape than we had committed ourselves to supplying,” Dr. Westerhoff notes. ”At certain positions, we were not allowed to deviate from these values by more than 40 micrometers,” he explains. This corresponds to about half the thickness of a hair. In addition, customers are demanding that their prized possession feature a rather sophisticated geometry. In order to provide sharp images of the sun, the mirror must have an aspherical shape. This means the surface needs to have a different curvature radius in the middle than along the outside rims. “We did a much better job on the envelope than the order called for,” Dr. Westerhoff notes. This made it easier for Carl Zeiss in Oberkochen to do the polishing. ”Nevertheless, the greatest challenge was to involve both our personnel and technology in the manufacturing process as effectively as possible,” adds Thomas Werner, the production manager responsible. During the three-month processing phase, more than 450 geometric characteristics with tight tolerances were produced without any defects. GREGOR is equipped with adaptive optics that compensate for the effects of unsteady weather in Europe’s atmosphere on the image of the sun, which would otherwise be unclear. The astronomers are now able to observe even the smallest structures only 50 kilometers in size on the surface of the sun, which is roughly 150 million kilometers away. As soon as the telescope that is being built by the Kiepenheuer Institute of Solar Physics in Freiburg, the Astrophysical Institute of Potsdam, the Institute for Astrophysics in Göttingen and the Max Planck Institute for Solar System Research has been completed, its instruments will enable it to measure many of the features of the central star with unprecedented precision. This is particularly true for its variable magnetic field that is said to be responsible for sunspots, as well as outbreaks of large amounts of solar material. When a shower of particles from these eruptions hits the earth, they not only cause the fascinating polar lights, but can also destroy the electronics in satellites or cause power failures and interrupt telecommunications. To make sure this doesn’t take us by surprise, GREGOR will continue to keep a close eye on what is happening up above us.