FLAGSTAFF, ARIZONA -- Galloping Galileo is nearing its swan song finale. The veteran spacecraft has been on the job probing giant Jupiter and its brood of moons since December 1995.

Now zapped by mega-doses of radiation, fighting a case of tape recorder disorder, its camera turned off and propellant nearly exhausted - the good ship Galileo is being readied to take its last scientific gasps.

Galileo has functioned in orbit more than three times longer than its originally planned mission.

The feisty spacecraft has survived about three and a half times as much exposure to radiation from Jupiter's radiation belts as it was designed to withstand. Looping around Jupiter, it has flown near Io repeatedly, also taking in views of Jupiter's planet-sized moons: Europa, Ganymede and Callisto.

"The next orbit is the last scientific data-taking orbit. It's called A-34. We're targeting Amalthea as the satellite in question," said Torrence Johnson, chief scientist for Galileo at the Jet Propulsion Laboratory (JPL) in Pasadena, California. "We're still working the exact aim point, but it's going to be within 310 miles (500 kilometers) of Amalthea.

Johnson was here participating in a study group focused on Europa exploration. He told SPACE.com that Galileo's high priority at Amalthea is to better understand the bulk density of the small Jovian moon. This is to be done by precisely tracking the spacecraft from Earth. By determining how Galileo is deflected during its close-in flyby, scientists can calculate Amalthea's mass.

Amalthea is heavily cratered and is irregular in shape. It is the reddest object so far seen within in the solar system and appears to give out more heat than it receives from the Sun. This may be because, as it orbits within Jupiter's powerful magnetic field, electric currents are induced in the moon's core. Or, the heat could be from tidal stresses heaped on the tiny world by giant Jupiter.

"Also, we'll be flying through the edge of Jupiter's gossamer ring. We're hoping to see information about particle impacts from our dust detector. Furthermore, the spacecraft is going deeper than we've ever been in Jupiter's magnetic field," Johnson said. The interaction of dust, particles and plasma will be interacting heavily within this region of Jupiter's magnetosphere, he said.

At present, Galileo's solid-state tape recorder is stuck in the stall position. "It's the first time this has happened since back before we got to Jupiter where we had this problem," Johnson said. That hardware has been put through the ringer, working far longer than its designers ever really anticipated, he added.

"It was not a total surprise that it stuck on us. The surprise, to a certain extent, is that we haven't had further problems with the tape recorder during the mission," Johnson said. Engineers are now looking at ways to condition the device, attempting to strategize how to restore its operation.

"We're proceeding slowly. People think there's every reason to believe we can probably unstick the thing. They'll be figuring out how much current the motor is taking in various modes. We think we've got enough torque authority, running it backwards, and get it going again," Johnson said.

Worse case is that the unit doesn't work.

That would mean loss of the ability to record at high data rates, then transmit that information back to Earth late in January. However, compressed data could be relayed back to Earth in a mode called real-time science. "So we would still get significant amounts of physics data back," Johnson said.

"I think there's a good chance we'll get the recorder running for one more go," the Galileo project scientist said.

There is one other remaining uncertainty.

What will happen to Galileo as it plunges so deep into Jupiter's radiation belts? "We'll be getting five to ten times more radiation than we took even on those passes by Io," Johnson said.

The fact that the spacecraft has behaved a little oddly during encounters with high radiation is not too surprising. "We've managed to get useful data on practically every encounter in spite of that," Johnson said. "But it'll be a big challenge going to Amalthea," he noted.

Since this is Galileo's last shot, spacecraft engineers are disabling fault protection modes within the probe. "We don't want to have the spacecraft get a bunch of yellow caution lights, shut down, and not get anything. We'd rather go ahead and take a little damage and come out the other end," Johnson said.

Coming out the other end turns Galileo into a short-timer.

The revered craft is then on a path putting it on a collision course with Jupiter in the fall of 2003.

Johnson said there is a proposal to leave a sequence onboard Galileo. The spacecraft could take data for the final couple of hours before slipping behind Jupiter into oblivion.

But given that the Galileo project formally ends in early January 2003, it'll take extra money and a still healthy spacecraft to perform that last curtain call for science.