Science and Health

Comet-hunting spacecraft shuts down after 12 years

Updated: 2011-03-25 22:24

DENVER - NASA ordered its comet-hunting Stardust probe to burn its remaining fuel on Thursday, setting off a sequence that shut down the spacecraft after a 12-year career.

Stardust had finished its main mission in 2006, sending particles from a comet to Earth. It took on another job last month, photographing a crater on an asteroid.

It accomplished one last experiment on Thursday, firing its thrusters until its last hydrazine fuel was gone. The length of that burn, a little under 2 1/2 minutes, will tell engineers exactly how much fuel was left so they can see how accurate their calculations were.

That in turn will help with the design and operation of future probes.

Spacecraft don't carry fuel gauges because they don't work in zero gravity.

It will take a few days to analyze the fuel data, said Jim Neuman, a mission operations manager for Lockheed Martin, which built and operated the probe at its complex south of Denver.

Engineers gave Stardust the order to begin its final burn at 4:41 pm local time. Once the fuel was gone, the probe lost its ability to keep its antennas pointed toward Earth, and the control room lost radio contact at 5:33 p.m. local time.

"Like saying goodbye to a friend," said Allan Cheuvront, the Stardust program manager for Lockheed Martin, who has worked on the probe since 1996, when it was in the detailed design stage.

He paused, fighting back tears.

"It's been an amazing spacecraft. It's done everything we asked, it's done it perfectly."

Since launching in 1999, Stardust has traveled 3.5 billion miles (5.63 billion kilometers). In 2004, it flew through a cloud of dust and gas enveloping the Wild 2 comet, capturing tiny samples. Those were sent back to Earth for study in 2006, via a parachute-equipped canister.

NASA then recycled Stardust, sending it past the Tempel 1 comet last month to photograph a crater left by a projectile launched by another space probe, Deep Impact.

If Stardust executed all of its final orders as expected, it put itself in "safe mode," turning most of its systems off, about 1 1/2 hours after the last command was sent.

With no fuel, Stardust can't keep its solar panels aimed at the sun, and once its batteries are drained it will shut down for good.

Stardust will be left in an orbit around the sun. Engineers project that in the next 100 years, Stardust won't get any closer than 1.7 million miles (2.74 million kilometers) of Earth's orbit or 13 million miles (20.9 million kilometers) of Mars' orbit.