"The 100-m telescope is better than ever before"

An interview with Michael Kramer on the scientific value of the 100-metre telescope at Effelsberg.

May 05, 2011

For four decades, a white dish has dominated the landscape around the village of Effelsberg in the Eifel. This is where the 100-metre telescope of the Max Planck Institute for Radio Astronomy was inaugurated on May 12, 1971. For many years it was the world’s largest fully steerable radio antenna and its huge dimensions still impress all who see it. In scientific terms, as well, the precision instrument has accomplished a great deal. We talked with Michael Kramer, one of the four Institute Directors, about the telescope’s past and its future.

How do you make the telescope fit for the future?

As we have done in the past, we would like to increase the sensitivity of the telescope even further. However, it is almost impossible or too expensive to enlarge it. Formerly, researchers regularly tried to improve the amplifiers of our receiver electronics. But even here our engineers are at the limit of what quantum mechanics allows. Two possibilities therefore remain: to enlarge the simultaneously measured frequency range or the size of the sky sector observed. The latest electronics and digital technology mean that both have become possible in recent years, as never before. We are therefore working on receivers and systems with very large bandwidths which enhance the range of vision by a factor of ten or more. This not only means we can survey the sky more rapidly, we can also take the liberty of increasing the “exposure time”.

How do you see the future of observing radio astronomy?

It is clear that at the high radio frequencies the new ALMA telescope in Chile represents the future. At the lower frequencies, which Effelsberg covers, the future is quite clearly in the combination of high survey speed and high sensitivity. As I indicated, this is where the 100-metre telescope plays an important role. In the long term, however, the ambitions are much, much greater! In around 15 years’ time a radio telescope is to be operated in the southern hemisphere which will exceed the receiving area of Effelsberg by a factor of 100! Since we are not able to build one individual telescope that large, it is synthesized from a network of smaller telescopes which are electronically connected. This Square Kilometre Array is not only a hundred times more sensitive, but also has a survey speed which is 10,000 to 100,000 times higher than that of existing telescopes. Astronomers from 20 different countries are already getting excited about what might be possible with such a telescope.

What is motivating radio astronomy at the moment? Which mysteries must be solved?

Owing to the diversity of the research which is possible, various colleagues would again provide different answers here. But I believe they would agree with me when I say that, on the one hand, we want to understand how complex molecules, stars and planets are formed. And on the other, we are also working on much more fundamental questions: how did the structure in the cosmos form, how – and when! – has the universe changed as a result of the formation of the first stars and galaxies? What is dark energy? Is it a new force of nature or the breakdown of Einstein’s general theory of relativity? This last question, in particular, is what spurs me on personally. And we can expect that radio astronomy can and will provide the decisive answers - especially in relation to this issue, as it has done in the past.

Interview: Helmut Hornung