Final approach for NASA's Saturn probe

By Tariq Malik

updated 5:49 p.m. ET June 3, 2004

Nearing the end of its seven-year, roundabout trip to Saturn, the Cassini-Huygens spacecraft has primed its engine and other systems for a swing past one of the planet's moons and the ultimate arrival at the ringed planet itself this month.

Then the real mission begins.

"The spacecraft is functioning very well, and it's just a matter of letting things continue," Robert Mitchell, NASA's Cassini program manager, said during a mission briefing Thursday at NASA Headquarters in Washington.

Cassini is now steering toward the small Saturnian moon of Phoebe following a flawless six-minute course correction last week. During that short engine burn, Cassini used all the systems it will muster for its orbital encounter with Saturn on June 30.

Earl Maize, deputy program manager for the Cassini effort at NASA's Jet Propulsion Laboratory, told Space.com that mission controllers have been practicing operations for that final orbital insertion maneuver, a 96-minute burn that will twice carry the spacecraft through the plane of Saturn's rings.

Previously in the mission, spacecraft handlers conducted an eight-day dress rehearsal of Cassini's Saturn approach in which the spacecraft turned and underwent every maneuver but engine firing, he added.

The crucial burn will slow the spacecraft to allow orbital capture. Cassini's main engine will be turned to face the direction of travel during the burn. The thrust will act like a brake.

Mission planners said Saturn is about as big as the full moon for Cassini right now, and the spacecraft should pass by at planet's moon Phoebe, a 136-mile (220-kilometer) satellite, on June 11. A 30-hour flyby session will bring the craft within 1,243 miles (2,000 kilometers) of the moon at its closest point, giving researchers their closest look at Phoebe ever.

Phoebe orbits Saturn on a reverse path, called retrograde, leading scientists to believe it is a captured asteroid or Kuiper Belt Object.

Free video Mission to Titan June 3: Huygens project scientist Jean-Pierre Lebreton describes the European probe's mission to Titan. NASA

About a week later, Cassini will ignite its engine to make a one last course adjustment, expected to be about a one-minute burn to align it properly for orbital insertion at the end of the month. Since the orbital insertion maneuver will bring Cassini the closest to Saturn's ring than at any other time in its mission, the spacecraft will conduct some ring studies during the maneuver, researchers said.

Launched in October of 1997, the Cassini-Huygens mission is a joint effort by NASA, the European Space Agency and the Italian Space Agency, to study Saturn's atmosphere, rings and many moons for at least four years. The Cassini orbiter carries the ESA-developed Huygens probe, which is due to visit Titan, Saturn's largest moon and the only satellite in the solar system to boast a dense atmosphere, on Dec. 24.

Cassini will enter orbit around Saturn on July 1 GMT, which will be late June 30 in the United States.

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