London, 31 May 2004 (RFE/RL) -- A strange dark moon of the planet Saturn, Phoebe, is now set to become the first exploration target of a huge, six-ton American-European robotic spacecraft.
The craft is currently closing in on the ringed planet, some 1,500 million kilometers from Earth.
Scientists were pleased that the main engine of the "Cassini" spacecraft fired successfully for six minutes on 27 May, as it had not been tested for five years.
"I would guess the new things we are going to see -- particularly if the Huygens probe works, and we may actually get pictures of what it's like to be on Titan -- I think that could be very exciting."
This maneuver has now set the stage for a close encounter -- "Cassini" is set to pass Phoebe at a distance of only 2,000 kilometers in less then two weeks time, taking pictures and measuring Phoebe's composition.
The "Cassini" spacecraft -- named after the astronomer who discovered a dark gap in Saturn's rings 350 years ago -- will pass Phoebe on the way to the vicinity of Saturn's rings.
Clive Simpson is the editor of the British Interplanetary Society's "Spaceflight" magazine. "I think it will be very interesting to see what kind of images they can pick up during that fly-by, and really, we are sort of waiting almost on the edge of our seats, I suppose, to see what kind of information it can return," Simpson said.
Simpson adds that "Cassini" will be able to take photographs of Phoebe that are a thousand times better than those snapped during the fly-by by the "Voyager 2" spacecraft in the early 1980s from a distance of over 2 million kilometers.
Those photographs showed only that Phoebe was very dark and irregular in shape, and it moved in the opposite direction around Saturn than its other moons.
But "Cassini" is able to take other measurements that scientists say should confirm that the 220-kilometer-wide moon really is a captured object from the distant Kuiper Belt, beyond the solar system.
If this is confirmed by "Cassini's" close encounter, it will give scientists important clues about the origin of our solar system from that far-out region.
After exploring Phoebe, "Cassini" will slow down and enter Saturn's orbit, becoming its first artificial satellite. The spacecraft will then conduct a four-year exploration of Saturn's moons and rings, passing many of them several times at various angles and distances. Scientists and experts anticipate that significant discoveries should take place.
"As far as I understand, the 'Cassini' spacecraft is in an excellent state of health, and everything is working quite normally. I think because it is going to be the first spacecraft ever to go into orbit around Saturn, then it is obviously going to be of huge excitement to space scientists and people in general all over the world," Simpson said.
Mark Hempsell heads the department of space engineering at Britain's Bristol University. He agrees "the exciting times are about to begin," but adds the mission is extremely demanding as far as the performance of the spacecraft itself is concerned.
"I guess, because I am an engineer, I am actually just keen that the mission works, that the engineering works. It's a very, very complicated spacecraft, and just to see the whole thing work and give the scientists all they want, would be very exciting," Hempsell said.
Simpson adds that in addition to getting all the pictures and measurements of various moons, the spacecraft will send the small European-built "Huygens" probe to the surface of Saturn's largest moon, Titan, at the end of this year.
"I think Titan is probably one of the most interesting moons in the whole solar system, and again, it's got huge potential for the discovery of methane, or possibly very primitive forms of life. Really, at this stage, we can't say, but I think it's going to be a very exciting time in the next six months, as we get information from both Cassini and the Huygens probe," Simpson said.
Hempsell agrees that to land a probe on Titan -- the second-largest moon in the solar system, and one that is shrouded by a dense nitrogen atmosphere and may have a sea of liquid hydrocarbons -- is going to be "very exciting for many people."
"I would guess the new things we are going to see -- particularly if the Huygens probe works, and we may actually get pictures of what it's like to be on Titan -- I think that could be very exciting," Hempsell said.
Hempsell points out that the "Cassini" spacecraft may make discoveries comparable to the enormous success of the "Galileo" spacecraft that explored the planet Jupiter.
"If all the bits work, we should get something of the equal of 'Galileo' -- with maybe a little bit extra, because we have not done quite the same pre-emptive work on Saturn that we had on Jupiter, so there are more new things to be found," Hempsell said.
The "Cassini"-"Huygens" mission is truly international, as the twin spacecraft are the work of scientists and engineers from the United States, the European Space Agency, Italy and other countries, including the Czech Republic.