By Michael Miller
Pasadena, California - Nasa's veteran space traveller Galileo, which has been exploring Jupiter and its moons for the past four years, will team up with space newcomer Cassini for the first-ever joint observation of a planet by two spacecraft, the United States space agency said on Thursday.
"For the first time ever, two spacecraft will simultaneously explore an outer planet," Cassini Project Scientist Dennis Matson said at the National Aeronautics and Space Administration's Jet Propulsion Laboratory in Pasadena.
"One spacecraft will be inside Jupiter's magnetic envelope, with the other outside where it can observe the powerful solar wind pressing on the envelope. From the two vantage points, we'll watch cause and effect as the wind changes the magnetic properties around Jupiter," he added.
Galileo Project scientist Torrence Johnson described the joint mission as a "unique opportunity to study this dynamic system with two highly capable spacecraft at the same time. It's a real bonus for both missions."
Galileo has amazed scientists with its stamina. Launched in 1989, the craft arrived at Jupiter in 1995 for a two-year mission that was supposed to end in December 1997. Now, its planetary passport has been extended at least until the end of this year, when it will team up with Cassini.
"This extended travel ticket enables us to continue studying Jupiter and its fascinating moons," said Galileo Project Manager Jim Erickson.
Cassini, which was launched in October 1997, is due to visit Jupiter's neighbourhood in December 2000 on its way to Saturn, stopping off to perform its joint mission with Galileo. It will then use Jupiter's powerful gravity in a "slingshot" manoeuvre to propel it to Saturn, Nasa said.
Before teaming up with Cassini, Galileo will perform two more flybys of the Jovian moon Ganymede, the largest moon in the Solar System. These are scheduled to take place on May 20 and December 28.
Scientists at the Jet Propulsion Laboratory hope these flybys will tell them more about Ganymede's geological history and will include the highest resolution pictures ever taken of the Jovian moon's icy world.
"As Galileo continues operating in Jupiter's harsh radiation environment, it's a challenge for our operations team to keep the spacecraft healthy. But we like to think of Galileo as the 'little spacecraft that could,'" Erickson said.
Galileo mission planners currently are exploring various options for the mission's eventual conclusion, including possible further encounters with the fiery volcanic moon Io and another Jovian moon, Callisto.
Planners also are looking into a possible impact with Io, or even Jupiter itself, for a blazing mission finale, but they are trying to avoid an impact with Europa, because recent evidence suggests there may be a liquid ocean beneath its icy crust, raising the possibility that life could exist there.
By April 2001, Galileo will have travelled nearly 4,5 billion kilometres and the Jet Propulsion Laboratory has estimated that on Earth, that mileage would earn a frequent flyer nearly 85 000 free round-trip tickets to Hawaii, an area with volcanoes remarkably similar to those on Io. - Reuters