Spacecraft to make flirty flyby of comet

CORNELL (US) — Astronomers are anxiously awaiting the Valentine’s Day rendezvous between the Stardust spacecraft and the comet Tempel 1.

The two orbiting bodies will meet, about 120 miles apart. As they pass, Stardust will test the density and composition of the dust surrounding the comet and snap 72 high-resolution images.

Researchers expect to receive the data within a few hours of the closest encounter. “The science team is awfully excited,” says Joe Veverka, Cornell University professor of astronomy and principal investigator for Stardust-NExT, the NASA mission orchestrating the rendezvous.

The Valentine’s Day flyby could yield a wealth of new information about Tempel 1’s structure and composition, Veverka says, and how its features change with every passage around the sun.

“We know that comets lose material,” he said in a recent press conference; “But the question is ‘How does the surface change, and where does the surface change?'” Comparing the 2005 images taken by the Deep Impact spacecraft with the new ones—taken one rotation around the sun later—could provide the answer.

Closer look
Stardust could also catch a glimpse of the crater that formed when a probe from Deep Impact crashed into Tempel 1’s surface six years ago.

“That impact threw up so much ejecta that Deep Impact never saw the crater,” Veverka says. “So it could never see how big the crater is and what [it] tells us about the mechanical properties of the surface.”

That information is vital for any future mission that involves landing a spacecraft on the surface of a comet, he adds.

And finally, astronomers hope the rendezvous will provide a closer look at some of the surface features Deep Impact saw when it zoomed by Tempel 1. Layered terrain, for example, could contain information about how comet nuclei were formed; and smooth flows hint at some internal processes that could be working their way up to change the surface.

“Deep Impact saw only about one-third of the surface,” Veverka says. “We would like to see more.”

Veverka and colleagues have been tracking the pair hurtling toward each other at about 590,000 miles a day.

After the flyby, there will be months—perhaps years—of data analysis; and ultimately, plans for the next mission.

“Comets preserve some of the most faithful information about what happened when the solar system formed,” Veverka says. “This is a step toward the ultimate answer.”

Fated affair
This spacecraft and comet couple seemed meant for each other.

Stardust, launched in 1999, and her cometary fiancée, Wild 2, headed blissfully toward a 2004 rendezvous. Meanwhile, the comet Tempel 1, making her own solitary way around the sun in 2005, was heading toward a more explosive relationship with Deep Impact.

In 2006, Stardust tossed her dusty tokens of Wild 2 down to Earth for analysis and was ready for a second mission. Tempel 1, scarred by her violent encounter with Deep Impact, was looking for a kinder, gentler match. How appropriate the two would meet up on February 14.

Stardust-NExT is managed by JPL, a division of the California Institute of Technology in Pasadena, for the NASA Science Mission Directorate. Lockheed Martin Space Systems built the spacecraft and manages day-to-day mission operations.

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