The Southern African Large Telescope camera (Salticam) has taken its first pictures of galaxies and stars, the SA Astronomical Observatory (SAAO) at Sutherland in the Northern Cape said on Tuesday.
”The pictures that you see are not any better than anything else available, but they are proof of the camera. That the damn thing works,” Dr Darragh O’Donoghue, Salticam principal investigator.
The camera will be used as part of the Southern African Large Telescope (Salt) when it is completed and handed over for scientific use at the end of next year.
Engineers and scientists were still ”beavering away” at Salt, with its 11-metre mirror array, so the Salticam was tested using the much smaller Elizabeth Telescope at the SAAO Sutherland, said O’Donoghue.
The Elizabeth telescope only has a single one metre mirror, and about the same light-gathering power as just one of Salt’s 91mirror segments.
The Salticam is South Africa’s major contribution to the instrumentation that will make Salt a useful scientific tool for exploring the universe. When the Salt comes into operation, Salticam will be used to record digital images of distant stars, galaxies and quasars, O’Donoghue said.
Engineers and technicians at the SAAO have spent two years designing and fabricating the hundreds of tiny precision parts, and assembling them into a working camera.
Two weeks ago, SAAO technician Willie Koorts assembled the camera, working in the ultra-clean environment of a Class 100 laminar flow bench — an area the size of a kitchen cupboard, closed off from any pollutants such as dust, hair and saliva. He was gloved, robed and wired into the earth at the electrical mains supply in the wall to keep his body free of static electricity.
Carefully he opened the shipping container holding Salticam’s two charge coupled device (CCD) chips, each worth nearly R1-million and inserted them into the camera. The chips work in the same way as camera film, but are far more effective.
By way of explanation O’Donoghue has written a first person report from an imaginary ”cameranaut” inside Salticam: ”I am standing on the surface of one of the R1-million Salticam CCD chips, which stretches out for almost 60mm before me. Since I’m only one fiftieth of a millimetre tall, the far edge is almost beyond the range of what I can see.
”My protective suit shields me from the vacuum inside the cryostat, and keeps me from freezing in the -73 degrees Celsius temperature where I am now. A fall into the yawning gap between the two CCDs (almost a millimetre wide) would expose me to the -120C temperature deeper inside this cryostat, killing me instantly as my
suit failed.
”Far above my head (5mm or so) is the cryostat window. Through it is pouring light emitted almost 12-million years ago by Centaurus A, a ‘radio galaxy’ which looks like a cosmic hamburger a hundred thousand light years across.
”Formed by the collision of two galaxies, Centaurus A is dominated by a spectacular disk of dust threaded with young stars.
”The light from Centaurus A, gathered by the 1m telescope, plunges down onto the grey-black silicon surface of the CCDs, generating electrical signals recorded as images in the Salticam control computer.” – Sapa
SA Astronomical Observatory’s website