As morning mist blankets the Puerto Rico hills, workers prepare to bring the ALFA unit (hanging from a cable at the left) into the Arecibo tele-scope's Gregorian dome, April 21.

The Arecibo Observatory telescope in Arecibo, Puerto Rico, the largest and most sensitive single dish radio telescope in the world, is getting a good deal.

In April the telescope got a new "eye on the sky" that will turn the huge dish, operated by Cornell for the National Science Foundation, into the equivalent of a seven-pixel radio camera.

The complex new addition to the Arecibo telescope was hauled 150 meters (492 feet) above the telescope's 1,000-foot- diameter (305 meters) reflector dish starting in the early morning hours. The device, the size of a washing machine, took 30 minutes to reach a platform inside the suspended Gregorian dome, where ultimately it will be cooled and then connected to a fiber optic transmission system leading to ultra-high-speed digital signal processors. The new instrument is called ALFA (for Arecibo L-Band Feed Array) and is essentially a camera for making radio pictures of the sky. ALFA will conduct large-scale sky surveys with unprecedented sensitivity, enabling astronomers to collect data about seven times faster than at present, giving the telescope an even broader appeal to astronomers.

The ALFA receiver was built by the Australian research group, Commonwealth Scientific & Industrial Research Organisation (CSIRO), under contract to the National Astronomy and Iono- sphere Center (NAIC) at Cornell in Ithaca. Development of ALFA was overseen by the observatory's technical staff. The rest of the ALFA system, including ultra-fast data processing machines, is under development at NAIC.

Radio telescopes traditionally have been limited to seeing just one spot — recorded as a single pixel — on the sky at once. Pictures of the sky have been built up by painstakingly imaging one spot after another. But ALFA lets the telescope see seven spots — seven pixels — on the sky at once, slashing the time needed to make all-sky surveys. Steve Torchinsky, ALFA project manager at Arecibo Observatory, said the new device will make it possible to find many new fast-spinning, highly dense stars called pulsars and will improve the chances of picking up very rare kinds of systems — for instance, a pulsar orbiting a black hole.

—David Brand, Cornell News Service