"Cassini-Huygens" will spend the next four years studying the ringed planet, which is considered one of the most fascinating in our solar system.
Tension was high during the last hour and a half of the seven-year-long mission, as the $3 billion spacecraft had to find its way safely through Saturn's rings, which are thought to consist of dust grains.
Mission scientists say particles only as big as peas or marbles could have done severe damage if they had hit the spacecraft. But all went well, and "Cassini-Huygens" went into its planned orbit faultlessly.
A jubilant Charles Elachi, director of NASA's Jet Propulsion Laboratory in Pasadena, described the mission by echoing the words of the first man to step on the moon, Neil Armstrong.
"This is a small step, another small step, in our quest of discovery that NASA and Europe are committed to do on behalf of all humanity. But it is going to be a huge leap in our understanding of the Saturnian system," Elachi said.
The spacecraft, launched from the southern U.S. state of Florida in October 1997, actually consists of two vehicles. One is the Cassini probe, which will spend its time orbiting Saturn, and which is designed to tell scientists more about the composition of Saturn and its moons. The planet -- the sixth away from the sun in our solar system -- is thought to be a solid core surrounded by an outer covering of liquid hydrogen.
One of the participating scientists, Michele Dougherty of the Imperial College of Science and Technology in London, explained "Cassini's" task by saying, "It's the time we get as close to Saturn as we are ever going to get. We are about 12,000 miles [19,000 kilometers] above the cloud tops. What that is going to allow us to do is to measure some of the fine detailed structure of the internal field. And that will be able to give us a better understanding not only of how the field is formed, but also hopefully give us a better understanding of the internal structure of Saturn," Dougherty said.
The second probe is the smaller "Huygens," which is scheduled to detach itself from the main assembly later this year and land on the surface of Saturn's biggest moon, Titan. Titan is particularly interesting because it is believed to resemble the Earth at an early stage of its development.
The two vehicles have been developed in a joint project involving the U.S. space agency NASA and the European Space Agency, as well as the Italian space agency.
The mission is the culmination of years of work, as NASA's Charles Elachi points out. Elachi is also team leader of the "Cassini" part of the project.
"This is a result of 22 years of effort, of commitment, of dedication, or ingenuity, and that is what exploration is all about," he says.
"Cassini-Huygens" marks the first time that Saturn and its 31 known moons have been observed in such detail. Previous NASA missions like "Pioneer 11" and the "Voyager" missions between 1979 and 1981 were only brief fly-bys.
Another Imperial College scientist, Nicholas Achilleos, gave more details about the current mission. "Between the [two craft], the instruments represent an enormous array of observational techniques. We have our instrument, the magnetometer, which measures magnetic field. We have plasma instruments which measure the properties of charged particles in Saturn's environment and the electric fields, and waves -- radio waves and plasma waves. Spectrometers which operate at ultraviolet, infrared, and visual wavelengths. We have imaging cameras," Achilleos said.
The aim, says Achilleos, is the most complete set of data on Saturn ever recorded.
The success so far of the Saturn mission follows two other successful NASA projects -- namely, the Mars rovers "Spirit" and "Opportunity," whose findings have helped scientists conclude that there was once water on the Red Planet.