Science: Update

FIGHTER AIRCRAFT crippled in the air could stand a better chance of making it back to base with the help of a novel form of computer software based in "neural nets" which are designed to mimic the activity of the brain. When the control surfaces of a combat plane are damaged there is little a pilot can do, reports New Scientist.

But Nasa engineers have shown that smart software can keep aircraft flying, even if some of their control surfaces are disabled. The tests took place at the Dryden Flight Research Center at the American National Aeronautics and Space Administration (Nasa) in California using a modified F-15 fighter aircraft, similar to those used in the Balkans. For the first time, neural nets were shown to be capable of keeping the damaged aircraft under control even at supersonic speeds.

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THREE OF the six gyroscopes used by the Hubble Space Telescope to keep its delicate orientation in space have now failed, as confirmed by Nasa this week.

The third gyroscope to fail began to behave erratically in January. Its loss means that the Hubble will have to stop operating if any of its remaining three gyros fail. "Any further gyroscope failure will cause the observatory to go into a protective safe mode that gives ground controllers complete control of the telescope, but prevents its use for taking observations of the sky," Nasa said. A repair mission is scheduled for later this year.

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AMERICAN SCIENTISTS plan to land a sundial on Mars so that people can monitor the Martian day via the Internet. The sundial will reach Mars in January 2002, carried on board Nasa's Mars Surveyor spacecraft, and is expected to be positioned near its equator. Much of the fabrication is being done at Arizona State University. The parts will be returned to the University of Washington in Seattle for final assembly, and the sundial is to be delivered to Nasa's Jet Propulsion Laboratory in Pasadena later this year.

This first extraterrestrial sundial will monitor the movements of a shadow over a Martian year, which is twice as long as Earth's. Mars's seasons are exaggerated - the planet's orbit is far more elliptical than that of Earth - so shadows vary greatly in length.

Steve Connor