NASA Spacecraft Tweaks Path Toward Comet

A NASA spacecraft zooming through the solar system fired up its rocket thrusters this week to fine-tune its approach to a bruised comet.

The Stardust spacecraft fired its thrusters Wednesday to tweak its planned 2011 arrival at the Comet Tempel 1. The probe delayed its arrival by just over eight hours, but that change maximizes the chances that the spacecraft will be able to catch the best views of the comet, mission managers said.

Comet Tempel 1 is a familiar one for NASA. The space agency intentionally slammed its Deep Impact probe into the icy wanderer in 2005 just to see what it was made of. But Stardust has less violent plans ahead.

Stardust is slated to swing by Comet Tempel 1 on Feb. 14, 2011 (Valentine’s Day), just under a year from now, to see how it has changed since the Deep Impact mission. It will be the first time a comet has been revisited by spacecraft from Earth.

Stardust’s mission was originally aimed at collecting samples of a different comet, called Wild 2 (pronounced “Vilt 2”). It successfully made that rendezvous in 2004 and sent its sample canister containing the comet bits back to Earth in 2006.

Since then, Stardust has been hurtling through the solar system. NASA recycled the spacecraft to point it toward Comet Tempel 1 in 2007, which began the new Stardust- NExT (New Exploration of Tempel) mission.

Stardust fired its engines for nearly 23 minutes during Wednesday’s maneuver while flying on the opposite side of the solar side of the solar system from Earth. It launched in 1999 and is currently sailing outside the orbit of Mars.

"We could not have asked for a better result from a burn with even a brand-new spacecraft," said Tim Larson, project manager for Stardust-NExT at NASA's Jet Propulsion Laboratory, Pasadena, Calif. , in a statement. "This bird has already logged one comet flyby, one Earth return of the first samples ever collected from deep space, over 4,000 days of flight and approximately 5.4 billion kilometers (3.4 billion miles) since launch."

Stardust’s brief engine maneuver is a bit of cosmic insurance for NASA scientists. It slowed the probe’s flight speed by about 54 mph (87 kph).

By performing the engine burn, Stardust altered its trajectory toward Comet Tempel 1. The change should maximize the chance that parts of the comet seen during the Deep Impact mission will be bathed in sunlight when Stardust swings by to snap new comet photos with its high-resolution camera.

In addition to the new comet photos, Stardust is expected to record the composition, distribution and flux of dust in the coma – or head – of Comet Tempel 1. Scientists hope the mission will unlock a treasure trove of new insights into how similar comets formed 4.6 billion years ago.

"Stardust-NExT will provide scientists the first opportunity to see the surface changes on a comet between successive visits into the inner solar system," said Joe Veverka, principal investigator of Stardust-NExT from Cornell University in Ithaca, N.Y. "We have theories galore on how each close pass to the sun causes changes to a comet. Stardust-NExT should give some teeth to some of these theories, and take a bite out of others."

• Images - Stardust’s Comet Journey,The Landing
• Video - Watch the Re-entry of Stardust’s Comet Samples
• Deep Impact's Top 10 Comet Crash Images