NASA's comet-hunting spacecraft Stardust shuts down

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 p.m.
MDT. 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.

"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. 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 of Earth's orbit or 13 million miles of Mars' orbit.