Japanese Spaceship Tries to Bring Cosmis Dust Back to Earth

Correction, June 14: An earlier version of this story mistakenly asserted that the Japanese spaceship called Hayabusa was the first to land on an asteroid. While other spacecrafts have landed on asteroids before, Hayabusa was the first to touch down and then blast off again.

(June 11) -- Astronomers may be about to get their hands on the first dust gleaned from a rock floating in space -- if the beleaguered spaceship that's supposed to be carrying the dust delivers it safely home to Earth.

The Japanese spaceship called Hayabusa has already survived the perils of Pauline during a voyage covering billions of miles. Sunday, the Hayabusa faces its final, most critical test.

As it sails by the moon, Hayabusa is supposed to release a canister roughly the size and shape of a football that will plummet to a touchdown in the Australian outback. Inside the container, scientists hope, is a precious cargo of dust from an asteroid that Hayabusa landed on in 2007.

If Hayabusa does drop some asteroid dust into researchers' hands, it "would be extremely exciting," says Andrew Cheng of the Johns Hopkins Applied Physics Laboratory in Maryland.

Of course, "it will be a terrific disappointment if we don't have a sample," adds Cheng, who already has analyzed some of the data Hayabusa radioed back to Earth.

Scientists and aerospace engineers from around the world will tune in Sunday to Hayabusa's final adventure. After the sample canister is turned loose, it will plummet through the atmosphere, heating up into a 5,300-degree fireball.

Meanwhile, Hayabusa itself will break up into harmless debris.

If all goes according to plan, a parachute will open and cushion the canister's fall to the ground. It's estimated to land at roughly 10 a.m. EDT somewhere in the Woomera Prohibited Area, a remote military testing ground in the deserts of south-central Australia. Searchers will follow radio signals to scoop up the canister. Then it will be shipped to a facility belonging to the Japanese Aerospace Exploration Agency, which operates the spacecraft, for analysis.

Astronomers hope they won't see a repeat of the fate that befell one of the two other unmanned spacecraft to return to Earth from deep space. In 2004, the NASA spacecraft Genesis smashed into pieces in the Utah desert after its parachute failed to open.

A spacecraft's high speed as it streaks toward Earth means that re-entry is "the most critical [phase] in terms of the damage you get if it's just slightly wrong," says planetary scientist Simon Green of The Open University in Britain. "You have to enter the atmosphere at just the right angle or you bounce off or burn the spacecraft up."

Mission control must steer the spacecraft with extreme precision to prepare it to plunge into the Earth's atmosphere, says Shyam Bhaskaran of NASA's Jet Propulsion Laboratory, which is helping the Japanese guide Hayabusa home.

The required accuracy is like having "to throw a ball from here in Los Angeles and hit a spot about 3 feet wide 40 miles away in Santa Monica," he says.

Then there are the questions over whether the canister will in fact be ... empty. Hayabusa twice approached its target asteroid, named Itokawa, in 2007. The ship was not supposed to land, but it did, before Mission Control lost contact with it. No one is sure whether the technology to collect dust from the asteroid's surface actually worked.

At best, say scientists, there will be a sprinkling of dust inside Hayabusa's canister. That could be enough. Modern laboratory techniques can wring valuable data out of a dust pile weighing less than a flea. Even a tiny bit would shed light on the asteroid's composition, which itself would illuminate the ingredients found in the early solar system.

If the canister does make it to Earth intact, it would be a triumph, whether it holds any asteroid dust.

Somehow Hayabusa has survived problems like these that would have finished off a lesser ship:

• Two of the three devices that keep it pointed in the right direction have stopped working.
• A fuel leak led to a seven-week communications blackout in 2005.
• Several of its high-tech engines no longer function.

"We all thought the mission was over more than once," Cheng says. "But unbelievably, they managed to find a way to carry on. I guess that's the samurai spirit."