NASAs Galileo spacecraft fired its thrusters Tuesday to adjust its course for a second pass by Jupiters moon Io, as well as to position itself for possible future flybys of jovian satellites, although the future of the mission remains unclear.
The firings should put the orbiter, managed by NASAs Jet Propulsion Laboratory, within 186 miles (300 km) of the volcanic moons south pole on Nov. 25.
That flyby could be the missions final data collection effort because Galileos funding, already extended for two years beyond its primary mission, runs out at the years end.
JPL and NASA headquarters have been haggling in recent weeks over how much money it would take to extend the mission again.
Galileos primary mission ended in December 1997 but NASA approved more money so the spacecraft could take a closer look at Jupiters four largest moons especially Europa, which has been found to have an icy crust possibly harboring an ocean, and maybe even life below.
"We havent quite come to a budget agreement with JPL," said NASA spokesman Doug Isbell.
"If they come up with a plan that we would accept, wed sign it contingent on a successful final flyby of Io," he said.
The mission has completed 25 passes by jovian moons since it arrived at Jupiter in December 1995,
although data went uncollected on two of those flybys because the spacecraft was hidden behind the sun. It passed successfully by Io for the first time on Oct. 11.Currently, Galileo is approaching apojove -- the part of its orbit farthest from Jupiter before the spacecraft heads back toward the planet and Io.
Scientists want to take Galileo by Ios pole, rather than by its equator as in the previous pass, because it is easier at the pole to tell if the moons magnetic field is generated by Io alone, or also by Jupiter.
The firing on Tuesday, divided into six segments, started at 4:30 a.m. PST and was to end about 12 hours later.
"Weve been on a trajectory that was pre-planned for the Galileo Extended Mission," said project manager Jim Erickson. "Now were tacking on a flight change so that an option is available for headquarters to extend the mission."
The redesigned thruster firing will put Galileo in a position where it can swing past other moons and use their gravity to steer toward scientifically interesting sites in the jovian system. Otherwise, Galileo would circle Jupiter randomly with little chance of passing close to any of the planets moons.
Galileo continued this week to return data from the Oct. 10 flyby, some of it for a second or third time because it was lost in earlier transmissions. Some camera images came back scrambled.
Galileo returned spectrometer and camera data earlier this week of Ios Pele volcanic region taken while the area was on Ios night side.
Scientists will search for thermal emissions from the Pele caldera and possible hot glowing lava near Peles volcanic vent.
Later this week, scientists expect to get data that includes high-resolution images of the Pillan volcanic region. The images were taken at daybreak on Io.
Other incoming data should include images of the Colchis Montes region and high-resolution images of the Zamama volcanic vent.
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