The Galileo space probe, in a do-or-die effort, came within 380 miles of Jupiter's volcanic moon Io late Sunday in a splendid finale to its four-year mission.
"Everything looks really fine," said project manager Jim Erickson at NASA's Jet Propulsion Laboratory in Pasadena.
The intense radiation emanating from Io risked crippling the spacecraft's computers and guidance systems. But an hour after the craft had its closest encounter with Io at 10:06 p.m. Pacific time [2:06 a.m. Monday Eastern time], Erickson said all systems were functioning normally.
Duane Bindschadler, Galileo's manager of science operations, said that "Io is a natural laboratory for volcanoes. By studying Io close-up, we will learn more about how and when volcanoes erupt and why they act the way they do. This may even help us predict the behavior of volcanoes on Earth."
Wayne Sible, the project's deputy manager, acknowledged that sending the Galileo probe so close to Io, which gives off an intense field of natural radiation, could have been fatal to the spacecraft. But he said the encounter was worth the risk, given that Galileo had successfully completed its two-year mission of photographing and sending back data from Jupiter, plus another two-year extended mission around the planet.
"There was a possibility, if enough damage was done to the electronics, it would not survive the flyby. Because of this possibility, we planned the Io encounter for the end of the two-year extended mission," Sible said.
After the successful mission around Jupiter it seemed reasonable "to take a calculated risk for a much closer look at such a scientifically rich target" as Io, he added.
Erickson said Galileo did experience computer problems during its encounter with Io when it passed through the densest part of the Jupiter moon's radiation belt. "But we were able to bypass the problem and reset the computer. Whether it was the radiation or another problem we will probably never know."
Scientific data on Io from Galileo--which lost its ability to transmit through its high-gain antenna early in its epic journey--was not expected to reach Earth until November after being transmitted through its low-gain antenna. But Erickson said Galileo was sending "still data"--position, time and trajectory--after the successful flyby.