Galileo Millennium Mission Status 02-22-2000

MEDIA RELATIONS OFFICE

JET PROPULSION LABORATORY

CALIFORNIA INSTITUTE OF TECHNOLOGY

NATIONAL AERONAUTICS AND SPACE ADMINISTRATION

PASADENA, CALIF. 91109. TELEPHONE (818) 354-5011

NASA’s Galileo spacecraft has scored another success by completing this morning’s third and
closest flyby of Jupiter’s volcanic moon Io, dipping to only 199 kilometers (about 124 miles)
above the fiery surface.

“We’re thrilled that this flyby went well. If all continues as planned, this new data will round out
our Io photo album and the wealth of information gathered during the Io flybys last October and
November,” said Galileo Project Manager Jim Erickson of NASA’s Jet Propulsion Laboratory.

The signal indicating that the flyby took place was received on Earth at 6:32 a.m. Pacific
Standard Time. The spacecraft’s camera and other instruments were poised to capture the
encounter with images and other observations. If all goes according to plan, the data will be
transmitted to Earth over the next several months for processing and analysis.

Io lies close to Jupiter in a region bombarded by intense radiation from the giant planet.
Because that radiation can wreak havoc with spacecraft instruments, components and systems,
each Io flyby has kept Galileo team members on the edge of their seats. Galileo has already
survived more than twice the radiation it was designed to withstand.

While approaching Io, the spacecraft experienced a radiation-related false reset of its main
computer. Onboard software correctly diagnosed this as a false indication, and went ahead with
the Io encounter unaffected.

During this latest flyby, Galileo’s science instruments collected data about the abundant,
ever-changing volcanic activity on Io, which will help scientists better understand volcanism on
Earth.

The flyby took place while Galileo was about 811 million kilometers (504 million miles) from
Earth. Additional information about the Galileo mission is available at http://galileo.jpl.nasa.gov .

Galileo has been orbiting Jupiter and its moons since December 1995. The spacecraft has
successfully completed its two-year primary mission and a two-year extended mission, and is
continuing its studies under yet another extension, called the Galileo Millennium Mission. JPL, a
division of the California Institute of Technology in Pasadena, manages the Galileo mission for
NASA’s Office of Space Science, Washington, D.C.

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