BBC News Online: Sci/Tech

Spacecraft fails to keep eye on job

Mission scientists said the close encounter between the Deep Space One spacecraft and asteroid Braille took place at 0446 GMT on Thursday more than 117 million miles from earth at a speed of 35,000 mph (53,000 kmph).

Using its automatic navigation system the probe flew within 15 miles (24 km) of the asteroid. The "face-to-face close-up" was by far the closest encounter a spacecraft has had with an object in the solar system without actually landing.

But data received at Nasa's Jet Propulsion Laboratory in California indicated the craft had lost sight of Braille 20 minutes earlier.

"This is analogous to mispointing a camera and getting a blank field of view," said project scientist Robert Nelson. "It's not very exciting if this hypothesis holds out."

Mission success

However scientists say that even without pictures the mission was still a success, validating 12 new technologies which will be placed aboard future probes sent out into the solar system.

Deep Space One is the first mission of Nasa's New Millennium Program, which tests new technologies for future space and Earth-observing missions.

"No science mission could rely on using the technologies until they've been shown to work in space," said deputy mission manager Marc Rayman. "Deep Space One took the risk so other missions wouldn't have to."

The main focus was on the probe's autonomous navigation (AutoNav) system, which gave it a mind of its own to guide itself to its target with minimal input from ground controllers.

Ion engine

Another instrument on board, designed to analyse charged particles known as ions near the asteroid, seemed to have been operating normally and scientists believe it could still help answer questions about the make-up of the asteroid.

The mission was also intended to test the effectiveness of Deep Space One's ion engine.

Earlier space probes have burned fuel, but the ion engine which drives the craft by sending out a stream of high-speed particles is considered preferable because they deliver 10 times more thrust than a conventional engine for a given quantity of fuel.

The development is expected to lead to smaller and lighter spacecraft which would be less expensive to launch.

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