Cassini Spacecraft Approaches Saturn Orbit

Known to some in the space community as “the last battlestar,” the Cassini-Huygens spacecraft this week is on the verge of finishing its 2.2-billion-mile trip to Saturn as it prepares to get closer to the ringed planet than any other craft in history.

Cassini-Huygens is set to slip between two of Saturn’s rings and then thrust into the planet’s field of gravity in a maneuver called the Saturn Orbit Insertion (SOI). Cassini then is expected to begin providing data on Saturn, its rings and its moons through the use of a dozen onboard instruments in the Huygens probe.

The craft, launched in October, 1997, to study Saturn and its amazing rings and magnetosphere, represents a space program that runs in stark contrast to the one recently announced by NASA, which has said its immediate aim is to restructure and streamline its space efforts.

Keep Going Cassini

NASA engineers directing Cassini from the Jet Propulsion Laboratory in Pasadena said they have programmed the spacecraft to carry on through any glitches or emergencies as it attempts the SOI, which NASA has said is the next most critical part of the mission, aside from its initial launch.

“Everything has to go just right,” said Cassini-Huygens program manager Robert Mitchell in a statement. “The burn must occur for all 96 minutes, the turns must occur at the right time, the computers must keep the sequence going even in the event something unexpected should happen. We don’t want Cassini to call home if a problem arises, we want it to keep going. That is precisely what we’ve told the spacecraft: Don’t stop, keep going until you’ve put in all 96 minutes of burn.”

The burn refers to an hour and a half of engine power Cassini will use to position itself properly into Saturn’s orbit.

Big Ship, Big Burn

Jeff Foust, editor of The Space Review, told TechNewsWorld that because of its size and the limited capability of existing launchers, Cassini has had to take the scenic route to Saturn, flying past Venus, Earth and Jupiter and using the gravity of each planet to slingshot toward Saturn.

“That’s why it’s taken nearly seven years since its launch to finally arrive,” Foust said. “I think, though, that the scientific return that Cassini will provide will be worth the wait.”

Foust, who said the engine burn is critical for Cassini to enter orbit and avoid flying right past Saturn, reported that indications suggest the engine is working fine.

Close for Rings

If Cassini-Huygens can successfully shoot itself into Saturn’s orbit as planned, the craft will sail approximately 12,427 miles above the clouds of Saturn, 10 times closer than previous flybys and closer than any craft ever.

Cassini is outfitted with a series of instruments from the European Space Agency to provide information on Saturn’s largest moon, Titan, which is the only moon in the solar system with a dense atmosphere “similar to the early Earth in deep freeze,” according to NASA.

“In a sense, Cassini and the Huygens probe are like time machines that will take us back to examine a world we’ve never seen before, a world that may resemble what our own world was like 4.5 billion years ago,” said Jean-Pierre Lebreton of the European Space Agency, mission manager and project scientist for the Huygens probe.

Foust said Cassini will likely be providing both scientists and the public many great images and other data about Saturn, its rings and its moons for at least the next four years, “perhaps considerably longer,” he added.

A Big, Old Classic

Foust said Cassini — sometimes called “the last battlestar” because it is the last large, expensive planetary mission that NASA will do for some time to come — contrasts with a NASA that has for a decade focused on smaller, less expensive and more frequent missions, an outgrowth of the “better, faster, cheaper” philosophy of former NASA administrator Dan Goldin.

Foust said the next mission that will approach the size and expense of Cassini will likely be the Jupiter Icy Moons Orbiter (JIMO), a large, nuclear-powered spacecraft that will study three of Jupiter’s largest moons: Callisto, Europa and Ganymede.

“JIMO isn’t planned for launch until around the middle of the next decade, though,” Foust said.

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