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ESO Signs Major Contract with INNSE for the Technologically Most Advanced Astronomical Telescope in the World

21 Gennaio 1986

An important contract was signed today in Milan, Italy between the European Southern Observatory and INNSE Innocenti Santeustacchio. It concerns the construction of a large astronomical telescope which will become the technologically most advanced in the world when it enters into operation in 1988.

An important contract was signed today in Milan, Italy between the European Southern Observatory and INNSE Innocenti Santeustacchio. It concerns the construction of a large astronomical telescope which will become the technologically most advanced in the world when it enters into operation in 1988.

The contract covers the fabrication of the main mechanical structure of the 25 million DM ESO New Technology Telescope (NTT), the preassembly in Europe and the disassembly and packing in late 1987. The NTT will then be shipped to the ESO La Silla observatory in Chile and the first astronomical observations will start during September/October 1988.

It is the first large telescope project for INNSE, part of ITALIMPIANTI (IRI-Finsider group), which has experience with the manufacture of large items for European science.

The ESO NTT will be the seventh-largest optical telescope in the world and the second-largest on La Silla, next to the ESO 3.6 metre telescope, installed in 1976. Its foremost advantages lie in a number of innovative technical solutions, which will facilitate operation, increase efficiency and reliability and, not the least, reduce the total cost to about one-third of what a classical telescope of this size would have cost.

The NTT is extremely compact (5 x 6 x 12 metre) and weighs only 120 tonnes (40 to the use of a "lightweight" (6 tonnes) main mirror which measures 3.58 m in diameter, but is only 24 centimetres thick. Since the mirror is lighter, the entire telescope structure can also be correspondingly reduced in weight.

However, such a thin mirror will become deformed by its own weight when the telescope moves. To overcome this, a system has been developed at ESO by which an "image analyzer" continuously monitors the shape of a stellar image in the focal plane and the deviation from the ideal shape. Corrective signals are generated for the main (primary) and the secondary mirror supporting structures, so that optical perfection is guaranteed. Part of this system is the active support of the primary mirror which has 75 active axial pads and 3 fixed supports.

This system represents a major breakthrough in telescope technology and will also be used in ESO's Very Large Telescope project (VLT), a 16 metre equivalent aperture instrument, planned for the 1990's. Similarly, it is expected that several other technical features, once tested at the NTT, can also be taken over by the VLT.

The NTT will be housed in a 250 tonnes octogonal building, 16 metres wide and 16 metres high, which will turn with the telescope around a common vertical axis. The design of the building emphasizes the need to exploit optimally the exceptional atmospheric conditions at La Silla, one of the best astronomical sites in the world with more than 300 clear nights per year.

Remote control of the NTT via satellite from the European Headquarters of ESO is planned. In this way, the observers will not have to travel to La Silla in order to use the NTT, resulting in important savings in time and money.

The NTT will be built by European firms according to overall ESO design. The 3.5 metre mirror of ZERODUR glass ceramics was successfully cast by Schott Glaswerke (Mainz, FRG) in July 1984 and will be polished by Zeiss (Oberkochen, FRG). A call for tender for the building is about to be issued by ESO.

Contatti

Richard West
ESO
Tel.: +49 89 3200 6276
E-mail: information@eso.org

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