NASA's Stardust spacecraft successfully completed a close flyby of asteroid Annefrank early Friday-Nov. 1-as an opportunity for a full dress rehearsal of procedures the spacecraft will use during its Jan. 2, 2004, encounter with it primary science target, comet Wild 2.
On that day, Stardust will fly within 75 miles of Wild 2's main body, close enough to trap small particles from the coma, the gas-and-dust envelope surrounding the comet's nucleus. Stardust will be traveling at about 13,400 miles per hour and will capture comet particles traveling at the speed of a bullet fired from a rifle. The main camera, built for NASA's Voyager program, will transmit the closest-ever comet pictures back to Earth.
|Location of Stardust trajectory. View from above the solar plane Credit: NASA/JPL
Stardust, launched in February 1999, is designed to capture particles from Wild 2 and return them to Earth for analysis. The spacecraft already has collected grains of interstellar dust. It is the first U.S. sample-return mission since the last moon landing in 1972.
"It turns out to be a tremendous plus because you end up having a full dress rehearsal more than a year ahead of the encounter," said Donald Brownlee, a University of Washington astronomy professor who is the mission's chief scientist. "It's a little like a dress rehearsal for a wedding - you expect things to be fine, but you practice just to make sure. If the unexpected does happen at the rehearsal, it's not a problem at the real ceremony."
Annefrank is about 4 kilometers (2.5 miles) across. Stardust passed within about 3,300 kilometers (2,050 miles) of the asteroid at 04:50 Friday, Universal Time (8:50 p.m. Nov. 1, Pacific Standard Time). Radio signals confirming the basic health of the spacecraft after the flyby were received about 30 minutes later via an antenna at the Canberra, Australia, complex of NASA's Deep Space Network, said Thomas Duxbury, project manager for Stardust at NASA's Jet Propulsion Laboratory, Pasadena, Calif.
Asteroid 5535 was discovered by prolific German asteroid hunter Karl Reinmuth in March 1942 but was not named Annefrank until long after World War II.
|First images of Annefrank asteroid from Stardust
Credit: NASA/JPL, U. Wash
The discovery came barely three months before Frank, a Jewish teenager, joined her parents, her sister and four others hiding from the Nazis in Amsterdam, Holland. For two years the group remained in their hideaway, subsisting with help from a small circle of outsiders. Anne recorded their life and her thoughts in a diary that was to become one of the world's most famous books. The group was discovered in 1944 and sent to Nazi concentration camps. All except Anne's father perished. Otto Frank survived the war and returned to Amsterdam, where he published his daughter's diary.
Stardust visually tracked the asteroid for 30 minutes as it flew by at a relative speed of about 7 kilometers (4 miles) per second, a major goal of this test opportunity. Although no dust was anticipated near the asteroid, the spacecraft's dust instruments were in use as they will be at Wild 2: the dust collector was open and the dust counter from the University of Chicago and dust mass spectrometer from Germany were turned on.
Brownlee said the Annefrank flyby is "a very good test," the kind that ideally every mission should have.
"When we have the comet encounter, we want as few first-time events as possible," Brownlee said. "This fortunate opportunity at the asteroid increases our probability of success next year at the comet."
Images and information from the flyby period are being transmitted from the spacecraft today and through the coming week. Stardust's scientists and engineers are analyzing the data to maximize the probability of success during the 2004 encounter with comet Wild 2.
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Don Brownlee (U of Wash)