Southern African Large Telescope: Camera for Africa’s Giant Eye Snaps First Pictures
Scientists and engineers working on the Southern African Large Telescope (SALT)
camera (SALTICAM) have achieved ‘engineering first light’, successfully using
this digital CCD camera to snap test pictures of galaxies and stars. SALT with
its 11-metre mirror array willl not be finished until December 2004, so SALTICAM
was tested using the much smaller Elizabeth Telescope at SAAO Sutherland. With a
mirror only 1.0-metre across, the Elizabeth Telescope has about the same
light-gathering power as just one of SALT’s 91 mirror segments.
Embedded Nano-journalism: The Inside Story
(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 60 mm before me. Since I’m only 1/50 of a mm tall, the
far edge is almost beyond the range of what I can see. My protective suit
protects me from the vacuum inside the cryostat, and keeps me from freezing in
the -73 C temperature where I am now. A fall into the yawning gap between the
two CCDs (almost a mm wide!) would expose me to the -120 C temperature deeper
inside this cryostat, killing me instantly as my suit failed.
Far above my head (5 mm 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 1-metre telescope, plunges down onto
the gray-black silicon surface of the CCDs, generating electrical signals
recorded as images in the SALTICAM control computer.
Made in South Africa
SALTICAM is South Africa’s major contribution to the instrumentation that will
make SALT a useful scientific tool for exploring the Universe. When SALT comes
into operation, this is the camera that will record digital images of distant
stars, galaxies and quasars. Engineers and technicians at the South African
Astronomical Observatory (SAAO) have spent two years in the design, fabricating
the hundreds of tiny precision parts, and assembling them into a working camera.
The Terror of Open-Heart Surgery
Two weeks ago, SAAO technician Willie Koorts stood in the ultra-clean
environment of a Class 100 laminar flow bench, gloved, robed and wired into the
earth at the electrical mains supply in the wall. His job: opening the shipping
container holding SALTICAM’s two CCD chips, each worth nearly R1M. Electrical
static could destroy the chips instantly; the slightest fleck of dust would
injure their usefulness. Normal breathing and heartrate returned only after the
CCDs were secured to the cryostat lid, placed to an accuracy of a few microns.
Forward into the Past
The pictures taken in these successful tests were only a beginning. When SALT is
ready for its camera, SALTICAM will record images of distant galaxies, stars and
quasars a billion times too faint to be seen by the naked eye — light that may
have taken more than 10 billion years to reach us; light from near the beginning
of time.
More pictures and human interest:
http://www.saao.ac.za/salticam
