Galileo's Long Goodbye

Galileo spacecraft approaches Jupiter moon Io (l), artist conception, 1999/10/11
NASA's aging spacecraft Galileo made a final flyby of Jupiter's moon Amalthea and is now in standby mode, marking the official end of the science-gathering portion of its 13-year-long mission.

"It gathered data past the point of passing Amalthea," said Guy Webster, a spokesman at the Jet Propulsion Laboratory in Pasadena. No other details of the flyby were available.

The intense radiation near Jupiter had been expected to cause glitches that would force Galileo into "safe mode" meaning the spacecraft could not transmit any information. In safe mode, spacecraft close down nonessential activities for their own protection until orders are received from mission controllers.

The spacecraft had entered standby mode on previous flybys of Jupiter. In each case, controllers were able to restore normal operations by transmitting new commands.

Galileo was put on a course to pass within 99 miles of Amalthea at 1:19 a.m. EST Monday. An hour later it was to have passed within 44,500 miles of Jupiter, the mission's closest approach to the giant planet.

The spacecraft had made more than 30 flybys of Jovian moons, but the swoop past Amalthea was its first.

Galileo's instruments were set to measure Amalthea's gravitational tug, which should allow scientists to calculate the moon's mass and density, providing important clues to its composition. No pictures were taken.

The measurements are expected to be Galileo's last before it slams into Jupiter in September 2003, at the conclusion of its 35th and last orbit of the planet. Even if controllers are unable to restore full operation of the spacecraft, it is already on track to hit Jupiter.

Galileo's destruction was planned to keep it from hitting the moon Europa, and possibly contaminating the moon with microbes from Earth. Europa's frozen surface is believed to cover a salty ocean that could harbor extraterrestrial life.

Galileo was launched on its $1.4 billion mission in 1989 and arrived at Jupiter in December 1995.