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On July 1, 2004 the Cassini-Huygens spacecraft will fire its main engine to reduce its speed, allowing the spacecraft to be captured by Saturn's gravity and enter orbit. The spacecraft will then begin a four-year tour of the ringed planet, its mysterious moons, the stunning rings, and its complex magnetic environment.

During the Saturn Tour, Cassini will complete 74 orbits of the ringed planet, 44 close flybys of the mysterious moon Titan, and numerous flybys of Saturn's other icy moons.

Cassini Spacecraft before launch.

Key dates of the Saturn Tour are:

June 11, 2004 (19:32 UTC): Flyby of the furthest moon orbiting Saturn, Phoebe, at an altitude of 2,000 km (1,243 miles).

July 1, 2004: Crossing of Saturn's Ring Plane during the spacecraft's critical Saturn Orbit Insertion sequence.

Dec. 25, 2004: 02:00 UTC Huygens probe separates from the Cassini orbiter and begins its 22 day journey to Titan.

Jan. 14, 2005: Huygens begins its descent through Titan's cloudy atmosphere, where it lands on the surface about two and half hours later. The probe is scheduled to encounter the upper fringes of Titan's atmosphere at 09:00 UTC.

Other highlights of the Saturn Tour include close encounters with Saturn's moons Enceladus, Titan, Hyperion, Dione, Rhea and Iapetus.

Launched from Kennedy Space Center on Oct. 15, 1997, the Cassini-Huygens spacecraft will reach the Saturnian region in July 2004. The mission is composed of two elements: The Cassini orbiter that will orbit Saturn and its moons for four years, and the Huygens probe that will dive into the murky atmosphere of Titan and land on its surface. The sophisticated instruments onboard these spacecraft will provide scientists with vital data to help understand this mysterious, vast region.

Cassini-Huygens is an international collaboration between three space agencies. Seventeen nations contributed to building the spacecraft. The Cassini orbiter was built and managed by NASA's Jet Propulsion Laboratory. The Huygens probe was built by the European Space Agency. The Italian Space agency provided Cassini's high-gain communication antenna. More than 200 scientists worldwide will study the data collected.

Given the enormous distance between Earth and Saturn, it would have been a waste to send a spacecraft to the Saturnian region and only take a few measurements. Thus, the Cassini orbiter and the Huygens probe are equipped with an array of sophisticated instruments and cameras able to collect images in many varying conditions and light spectra; from visible light to the infrared.

After a seven-year voyage that includes four gravity-assist maneuvers, Cassini will enter Saturn's orbit in July of 2004. It will then begin a four-year mission that includes more than 70 orbits around the ringed planet and its moons. Pointing its various instruments at carefully calculated scientific targets, Cassini will collect detailed data on Saturn, its rings and the 30 known moons orbiting this gas giant. The information will aid scientists in understanding this complex and fascinating region. Main scientific goals include measuring Saturn's huge magnetosphere, analyzing from up close those stunning rings and studying Saturn's composition and atmosphere.

Once the spacecraft's onboard recording device reaches capacity, it will point its high-gain antenna toward Earth and download the data through one of the 70-meter (230-foot) antennas of the Deep Space Network. Cassini will be sending home several gigabytes of data daily. The data will then be analyzed by more than 200 scientists worldwide.

Cassini's cloud-penetrating imaging system will also be able to map Titan, Saturn's largest moon. This is a task that none of the three previous NASA missions that flew by Titan were able to do because of the thick, hazy atmosphere that engulfs this celestial body -- the only moon in the solar system with its own atmosphere.

In December 2004, Cassini will eject the Huygens probe. After its 22-day coast, the cone-shaped probe will descend into Titan's cloudy atmosphere. Three sets of parachutes will deploy to slow the probe and to provide a stable platform for scientific measurements. Instruments on board will collect information about the atmosphere's chemical composition and the clouds surrounding Titan. The data will be radioed to the Cassini orbiter, which will then relay the data to Earth.

About two hours after entering Titan's atmosphere, the probe will land near the moon's equator. If Huygens survives the impact, the probe might be able to communicate with the spacecraft for a few minutes after landing on the frozen surface of Titan. Huygens will be the furthest human-made object ever to land on a celestial body.

Source: NASA