ESA Science & Technology - ESA's new camera will revolutionise the way astronomers observe the Universe

"By 1992/93 we understood theoretically that superconductors would be sensitive in the optical and near infrared region of the spectrum," says Tone Peacock, Head of Science Payloads Technology Division, about the genesis of the new camera. "In the case of a superconducting camera, each individual piece of light (known as a photon) is detected. Not only that, its time of arrival and its colour is measured."

During 1992, working with ESA astronomer Michael Perryman, they predicted this unique capability of superconductors and the impact such a revolutionary light sensor would have on the field of astrophysics.

The ability to 'tag' each photon with its arrival time and colour, coupled with the speed of the superconductor, is what makes S-Cam so attractive. Today, astronomers use Charge Coupled Devices, known as CCD cameras, to make their observations. CCDs are also used in digital cameras and video cameras. Essentially, a CCD catches light in the electronic equivalent of a bucket, known as a pixel. The drawback is that this method can only measure the brightness of a mass of photons. Neither can a CCD measure colour.

With the new device, as each photon arrives, S-Cam records when and where it hits the detector and its colour, then passes the information to a computer where it forms a comprehensive database about the celestial object being studied. With this goldmine of information, astronomers can look for simultaneous variability in the brightness and colour of celestial objects on time scales of well below a millisecond (one-thousandth of a second).

This would allow them to study the large number of rapidly varying celestial objects whose details have so far eluded astronomers. Among them are the cataclysmic variable stars, the optical explosions associated with gamma-ray bursts and the visible light emitted by pulsars, the dead hearts of stars.

Scientists at ESA's research laboratories (ESTEC) in the Netherlands have tested their S-Cam prototype instrument successfully at the William Herschel Telescope (WHT), a large telescope on La Palma, in the Canary Islands. The ESA team lead by the S-Cam instrument manager, Nicola Rando, conducted a series of week-long campaigns at the telescope from late 1999 through 2000 demonstrating all aspects of this powerful instrument.

One result shows a binary star system in which a white dwarf passes behind a red star. As the image dims, so the colour changes from blue to red indicating that the light is being absorbed by material streaming from the red star down onto a spot on the white dwarf. The precise time of this dimming allows the astronomers to determine the size and location of the spot on the white dwarf even though the star is many light-years from Earth. Another observation has easily determined the distance to ten far-off celestial beacons known as quasars.

This is only the beginning. At present, S-Cam works with just 36 pixels but the team are fabricating S-Cams with hundreds and thousands of pixels. Eventually, they will rival the millions of pixels that CCDs now possess. Their use will then extend to all branches of astronomy and beyond. Peacock envisages that they will eventually be taken up by the microchip industry. "I think the use of these chips to probe contaminants in silicon will become a major industrial application," he says.

Beyond that, who knows? One day, S-Cams may even find their way into household camcorders.