Comet threat averted

British space scientists were working this week to prevent the wreck of some of Europe's most important satellites by space debris.

John Zarnecki, of the University of Kent, was one of a team at the European Space Agency's technical centre in the Netherlands that closed the satellites in response to yesterday's threat from the Leonid meteor stream.

Satellites put into "safe mode" include two Earth-observing satellites, ERS-1 and 2, the Sun-observing satellite Soho and the Hubble space telescope, a mainly United States project in which ESA is a participant. Hubble has already been shut because of a broken gyroscope and will be repaired by a space shuttle mission next month.

Professor Zarnecki said: "ESA is also working to discover more about the structure of the Leonid meteor stream, which has never been fully mapped."

Optical and radio observations in Spain and elsewhere were expected, weather permitting, to yield the best-ever data on the Leonids. At their height, millions of pieces of comet debris per hour cross the Earth's orbit. Professor Zarnecki said: "The particles are very small, but they are moving at 70 kilometres a second, which means that an impact can penetrate a satellite easily."

Cutting edge, page 34