Pioneering Laser Measurement Technology Helps Track Origins of Universe
Between 2000 and 2005, South Africa and its German, Polish, American, New Zealand and UK partners will build the largest single telescope in the southern hemisphere, with a hexagonal mirror array 11 meters across. The Southern African Large Telescope (SALT) will be able to record distant stars, galaxies and quasars a billion times too faint to be seen with the unaided eye -- as faint as a candle flame on the moon.
Drawing of the Southern African Large Telescope currently under construction at Sutherland.
SALT is a flagship project, intended to demonstrate that the frontiers of science are not entirely reserved for the developed world. It will provide a first-class facility for fundamental research in Africa in a field where South Africa has a long history of excellence. It will strengthen ties with researchers around the world, and provide opportunities for young scientists and engineers in a stimulating high-technology environment. With a giant mirror gathering more than 20 times as much light as the largest existing African telescopes, SALT will have the power to tackle fundamental unsolved questions like:
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What was the Universe like when the first stars were forming, and quasars were common?
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What kinds of worlds orbit other suns?
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How are the stars in nearby galaxies different from stars near the sun?
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What can these stars tell us about the scale and age of the universe?
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How do quasars and gamma ray bursts outshine trillions of stars like thesun?
Cooperation with the South African Astronomical Observatory
SALT will be built near Sutherland on the South African Astronomical Observatory's sitein South Africa's Northern Cape Province. On this desert hilltop, far from city lights and pollution, SAAO has operated telescopes since the early 1970s. SAAO will also operate SALT, under contract with the SALT Board, and the SALT design- and engineering team is based at SAAO in Cape Town.
Measurements on SALT using the Leica Laser Tracker
The LTD500 Leica Laser Tracker system was brought to Sutherland at the joint request of Gerhard Swart of SALT and Pierre van der Merwe of main contractor RRS, to perform delicate precision measurements on the telescope itself.
John Mc Caffery, Product Manager Metrology, Setpoint Geomatics, SA remembers:
“We constructed special mounting brackets for the Tracker head as the measurements had to be carried out with the tracker mounted laterally. The intention was to mount the Leica tracker on the seeker tower looking into the dome of the telescope because of the visibility of many separate jobs, which could be carried out from this position. But due to turbulent air between the tracker and its targets, we had to mount the Leica tracker on the space frame holding the mirrors with the equipment computers ect. 5 meters below, a set-up, which worked extremely well”.
The main job was to measure the SALT tracker movements for being able to calibrat the telescope tracker.
South Africa’s Council for Scientific and Industrial Measurement Research (CSIR), one of the main investors in the SALT project were happy to see that the Leica Laser Tracker could perform the measurements, as a competitive product was unable to do the job due to technical limitations.
John Mc Caffery, Product Manager Metrology, Setpoint Geomatics , SA
