As it completed the first of three billion-mile “laps” around the heart of the solar system, NASA’s Stardust spacecraft made a “pit stop” of sorts in mid-January, flying by Earth for a gravitational speed boost. The spacecraft is headed for a comet, Wild 2, from which it will gather particles that may provide clues to origins of the universe. Donald Brownlee, UW professor of astronomy, is principal investigator of the Stardust mission.

“The flyby was a big event in the sense that it was a mission milestone,” says Brownlee, “but we didn’t have to do anything during the flyby. It was all celestial mechanics.”

Before Stardust’s January “visit,” engineers at NASA’s Jet Propulsion Laboratory made course changes and other adjustments to ensure that the spacecraft gained the proper amount of energy from Earth’s gravity. Stardust came closest to Earth—3,700 miles from the Earth’s surface near the southern tip of Africa—on January 15. It was traveling at about 22,400 miles per hour.

When Stardust finally has its rendezvous with the comet Wild 2 in 2004, it will capture particles being boiled off the comet’s surface by solar heating. The encounter will occur just outside the orbit of Mars, 242 million miles from Earth.

“The science of the mission is basically ahead of us,” Brownlee said. “We’ve dealt with a number of problems, but they have been fewer than most spacecraft experience.”

Perhaps the most heart-stopping problem came last November, when Stardust was bombarded by protons from a solar flare some 100,000 times more intense than normal. The energy overwhelmed the navigation camera, which is used to help pilot Stardust by focusing on stars and planets and then comparing that image with a star map in its memory. The spacecraft went into safe mode. Eventually the flashes faded, and ground controllers were able to reset the star camera.

There also has been some intriguing science, including analysis of interstellar particles the spacecraft encountered. “The surprise is that they were high-molecular-weight materials, probably large organic molecules,” Brownlee said. “It would be something analogous to tar or coal.”

Stardust’s next encounter with Earth comes in January 2006, when the return capsule—carrying comet material and interstellar dust particles—will separate from the spacecraft and parachute into the Utah desert. The particles will be sent to laboratories around the world for analysis. It is expected the samples will yield clues to the origins of the solar system and possibly life itself.

[Winter/Spring 2001 - Table of Contents]