South Africa is about to start building the second-largest telescope in the world , writes David Le Page
June 1 1998. A nervous astronomer sat in Parliament, waiting to hear then minister of arts, science, culture and technology Lionel Mtshali deliver his annual budget speech.
Director of the South African Astronomical Observatory (SAAO), Bob Stobie, knew that Mtshali was to announce the decision to provide 50% of the funding for a bold investment in hard science: the Southern African Large Telescope (Salt). But although the decision had already been ratified by the Cabinet, he feared the R50-million decision would be far from popular with MPs whose constituents have more immediate interests in houses and water supplies.
The announcement drew not mutters or disapproval, but a resounding round of applause from both the government and opposition parties.
Knowing national unanimity would make the task of raising another R50-million from foreign partners far easier, Stobie could breathe easier. It would still be over a year, however, before commitments from foreign partners could justify a decision to begin construction.
To understand the need for Salt in South Africa, one should first look 200E000 light years away, to the Large and Small Magellanic Clouds, two galaxies actually orbiting our own Milky Way galaxy, near the constellations of Dorado and Tucana respectively. Their irregular shapes are perhaps the result of inter-galactic collisions. Named for the first modern European explorer to view the southern skies, they are among a multitude of astronomic entities visible only from this hemisphere.
The southern skies are not unscrutinised, however. High in the Chilean Andes, a powerful 8m reflecting telescope is already under construction. Far larger than South Africa’s largest telescope, which is a mere 1,9m in diameter, the Chilean telescope is to have another considerable advantage: it sits at an altitude of 4 000m.
The 50-year-old South African Radcliffe reflector, near the isolated Northern Cape town of Sutherland, is at an altitude of only 1 800m, beneath far more intervening – and distorting – atmosphere.
Astronomers are as competitive in wrestling with lenses, light and mirrors as those who chase leather bladders across dusty pitches. Consequently, the 1,9m Sutherland telescope has frequently had its instrumentation, which receives and processes captured light, updated. But by the late 1980s it was becoming clear a replacement was required.
Frequently, South Africa’s position on the globe, both in longitude and latitude, makes it the only possibility for viewing critical events. The Sutherland observatory was first in capturing a spectrum from the supernova 1987A. A year before, it was the only telescope positioned to capture images during the encounter of the European Space Agency’s Giotto probe with Comet Halley. Moments of triumph feed ambition, and astronomers are no exception.
So in 1995, having decided a new telescope was necessary, a 4m design was proposed by the astronomical community. Cost-wise, it seemed the only practical option. But the proposal ignored the competitive spirit that awakens behind computer monitors during long, cold Karoo nights.
Stobie decided to gamble. He proposed that the 4m design be abandoned for a huge 10m telescope which would become the largest in the southern hemisphere, and share the honours for second-largest in the world with the Hobby-Eberly Telescope (HET) constructed at the McDonald Observatory in Texas. (The largest is the 10m Keck telescope at Mauna Kea, Hawaii.)
It would follow the HET’s radical new design: a fixed rather than moving primary mirror, which is segmented and spherical rather than solid and parabolic. Light is collected by a moving tracking and optical correction element.
The HET, though exceptionally well- endowed, is substantially cheaper than a conventionally designed reflector, costing 80% less.
The first step for the project was selling it to local astronomers and physicists, particularly the unusual design. This proved easier than anticipated, perhaps because all recognised the need for a comparatively low- cost proposal.
Next in line for persuasion was the Foundation for Research and Development (FRD), now the National Research Foundation, as it is the parent body of the SAAO. Fortunately, not only did the FRD buy into the idea, but chair Khotso Mokhele became one of the project’s most persuasive and passionate advocates.
The FRD in turn took the project to the Department of Arts, Science, Culture and Technology. Then, critically, it needed to be assessed by the Cabinet’s science and technology subcommittee.
In this, visits by Mtshali and then constitutional development and provincial affairs minister Valli Moosa to Sutherland may have proved critical. Moosa, a science graduate, spent two nights at Sutherland with staff during 1997.
Supporting the proposal to the Cabinet were letters of intent from the Hobbe-Eberly board in Texas promising access to all the plans and resources developed in building the first telescope. Carnegie-Mellon University in Pennsylvania and Goettinger University in Germany promised fund-raising assistance.
Salt, argued the proposal, will allow South African astronomers to produce groundbreaking science, dramatically shifting the country’s scientific profile.
As in the pursuit of any cutting-edge technological project, there are likely to be spin-offs which are difficult to predict. Airport X-ray machines were a spin-off from satellite-based X-ray astronomy.
Salt, being a spectrographic telescope which can analyse the chemical composition of the objects it scans, will attract scientists from a broad range of disciplines. It will be a flagship project not just for South Africa, but for the continent. It stands, through a planned science education centre, to inspire generations of youth to follow a scientific career: the Texan HET, despite being isolated, has attracted up to 100 000 visitors a year.
The Cabinet bit, and Mtshali was free to make his announcement in Parliament.
But the quest for the second 50% of funding bore fruit only in April 1999, when Rutgers University in New Jersey and Goettinger University pledged $1,2-million and $1,3-million respectively. Rutgers also pledged $1-million for operational costs.
Having secured certain early commitments, Stobie decided to go out on a limb. Rather than wait for all the necessary financial commitments before appointing a construction team, he used SAAO money to appoint Kobus Meiring project manager and David Buckley project scientist.
The SAAO is to be repaid this money from Salt funds. In the meantime, Meiring, who led the construction of Denel’s Rooivalk helicopter, and Buckley will be free to appoint a team from January. That team will fly to Texas to learn as much as possible from those who constructed the McDonald Observatory instrument. A ground-breaking (or rock-blasting) ceremony at Sutherland may be held as soon as April.
The entire project, though, will take five years to complete.
The construction of the mirror is probably the most fascinating aspect of the HET construction. It will comprise 91 hexagonal segments of glass with a zero expansion- coefficient: they will not change size with temperature. It will take three years to build the mirrors, as the equipment required to grind them into shape is so rare that they will have to be created one at a time.
However, should the basic structure of the telescope be completed before the mirrors are all ready, it can be put into commission with just seven of the mirrors in place.
One of the selling points of the telescope for Cabinet is likely to have been that at least 50% of its components can be constructed in South Africa, and so half the money invested in it will remain in the country.
Among these components is the optical tracking element and beam, which are moved robotically in three dimensions with a precision of a few microns across the broad top end of the telescope. There are two local companies capable of building it.
Among the projects anticipated for the telescope are looking back into the very early universe, to when it was 10% of its current age. It will be trained on galaxies with extremely energetic nuclei; on stars whose wobbly orbits betray the presence of planets; and on variable stars. It will follow the trail blazed by the Hubble Space Telescope, picking out more detail than the orbiting instrument is capable of, particularly in picking up spectra from extremely faint and distant objects.
Salt will be constructed with the possibility of upgrading it in the future to “rubber-mirror” technology, in which the actual shape of the main mirror is constantly adjusted by powerful computers in order to compensate in real-time for the distorting effects of the atmosphere.
Three weeks ago, on November 25, Dr Ben Ngubane, Minister of Arts, Culture, Science and Technology and Mtshali’s successor, gave the Salt board the go-ahead. The deciding event was a pledge from the Polish science minister for $3-million in support. The Polish agreement had depended on the two countries signing a science and technology co-operation agreement.
Salt still requires another $3-million in funding. But the project is now virtually unstoppable. Soon, South African astronomers will reach into the hearts of galaxies and 13-billion years back in time, masters of half the universe.
ENDS