NASA's Galileo spacecraft will encounter its second asteroid, called Ida, Saturday, August 28, on its way to Jupiter. Galileo made the world's first asteroid encounter -- with Gaspra --in October 1991.
At 9:52 a.m. Pacific Daylight Time (UTC minus 7 hours) Saturday, Galileo will pass within 2,400 kilometers (1,500 miles) of Ida at a relative speed of about 12.4 kilometers per second (28,000 miles per hour). Radio signals confirming encounter will reach controllers at the Jet Propulsion Laboratory 30 minutes later.
Galileo's camera and other scientific instruments will record observations beginning several hours before until several minutes after closest approach.
Because the spacecraft must use its low-gain antenna for all communications, the pictures and other data will be played back slowly in September and next 1994. "However," said Project Manager William J. O'Neil, "we will have a data set as good as Gaspra -- or better."
Ida is a stony body, irregular in shape and about 31 kilometers (20 miles) long. It is larger than Gaspra and orbits farther from the Sun. Ida is believed to belong to the same asteroid type as Gaspra, though younger and of slightly different composition.
Galileo will reach the planet Jupiter in December 1995. Its mission is to study Jupiter, its satellites and magnetosphere, using an atmospheric probe and an orbiter scheduled for a 10-orbit, 23-month survey. JPL manages the project for NASA's Office of Space Science.
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