Deep space probe heads toward comet

An artist's depiction of the Stardust's encounter with comet Wild 2.

By Richard Stenger
CNN Sci-Tech

(CNN) -- A NASA spacecraft has performed a critical course change in deep space, positioning itself for a rendezvous with a comet from which it will gather samples to return to Earth.

The Stardust probe fired its thrusters for nearly two minutes this month, quickening its speed for an approach to comet Wild 2.

After examining communication signals with the craft, mission scientists announced last week that it had completed the task successfully.

"This is the maneuver that sets us up for the bigger maneuver," said Robert Ryan, Stardust manager at NASA's Jet Propulsion Laboratory in Pasadena, California, in a statement. "It's a combination of increasing the speed of the spacecraft and at the same time putting it on the path to reach Wild 2.

"It's like the setup pass in a basketball game. Now we're ready to shoot the basket."

The robot ship should fly near Wild 2 in January 2004, collecting a thimble worth of particles from the dusty halo surrounding the comet's nucleus.

Stardust has overcome numerous difficulties since its 1999 launch, including blurry vision in its navigation camera and a mysterious case of excessive thruster firing. The $200 million mission is the first designed to bring back physical specimens from beyond the moon.

Scientists have said they expect Stardust's catch to shed light on many cosmic mysteries, including whether comets provided the water and organic material necessary to form life. Comets, possibly the oldest bodies in the solar system, could contain a record of the original material that formed the sun and planets 4.5 billion years ago.

The refrigerator-size, solar-powered craft also has been assigned the job of gathering interstellar dust particles streaming into our solar system.

The probe should return to Earth with samples of both in January 2006, landing via parachute in the Utah desert.

Currently, Stardust is more than 245 million miles (395 million kilometers) away from the sun.