Launched in October 15 '97, Cassini is the first spacecraft to orbit Saturn. The NASA orbiter is studying the intriguing features of Saturn's system of rings and moons. It also delivered the European Space Agency's Huygens Probe into the atmosphere of Saturn's moon Titan.
Just hours after it arrived at Saturn on June 30 2004,
the orbiter sent back surprising science data and images that shed new light on the structure
of Saturn's beautiful rings.
The orbiter's 4-year primary mission should reveal much about Saturn and its system of rings and moons.
The spacecraft is named in honor of Giovanni Cassini, the 17th century astronomer who discovered gaps in Saturn's rings.
Cassini is a truly international mission. Three space agencies and 17 nations contributed to the mission.
At a hefty 5,650 kilograms (13,230 pounds or about six tons), half of that is fuel for its manouvering rocket, Cassini is too heavy to travel directly to Saturn. No rocket on Earth can deliver that kind of power. The orbiter is about the same size as a 30 passenger school bus.
It was launched from the Kennedy Space Center in Florida by a Titan 401B-Centaur rocket and the spacecraft borrowed a little energy from Earth and twice from Venus to hurl itself into the outer solar system. This technique is called gravity assist.
These flybys gave scientists a chance to use Cassini's powerful instruments to take a peek at Venus,
Earth's mysterious cloud-cloaked neighbor.
Science instruments on the spacecraft searched for lightning in Venus' atmosphere during the flybys,
and the radar instrument onboard was activated to test a signal bounced off Venus' surface.
Physicists later reported that they detected no high-frequency radio waves commonly associated with lightning. The existence of lightning on Venus has been hotly debated since Russia's Venera spacecraft first detected potential signs of lightning in 1978.
"If lightning exists in the Venusian atmosphere, it is either extremely rare, or very different from terrestrial lightning", said physicist Donald Gurnett of the University of Iowa. "If terrestrial-like lightning were occurring in the atmosphere of Venus within the region viewed by Cassini, it would have been easily detectable".
With a speed boost, Cassini then hurtled through the asteroid belt and on to an exciting encounter with Jupiter. It entered Saturn's orbit on July 1, 2004.
Although Saturn is its primary destination,
Cassini's flyby of Jupiter uncovered a lot of new information about our solar system's largest planet.
Scientists used joint observations from Cassini and the Galileo spacecraft to reveal a vast,
invisible whirling bubble of charged particles surrounding Jupiter.
The bubble in Jupiter's magnetosphere reveals how the giant planet interacts with particles that stream off
our Sun.
The results helped scientists understand Earth's own magnetosphere which shields us from harmful
solar radiation.
Cassini also revealed Jupiter's radiation belts to be much harsher than expected - information that will help engineers protect future robotic spacecraft - and spotted new details in Jupiter's auroras. The spacecraft snapped hundreds of stunning pictures - offering a tantalizing glimpse of what it will reveal when it trains its lenses on Saturn - the jewel of our solar system.
After hitching a ride to Saturn aboard the Cassini orbiter,
the Huygens probe, supplied by the European Space Agency,
scrutinized the clouds, atmosphere, and surface of Saturn's most intriguing moon, Titan.
It was designed to enter Titan's atmosphere and parachute a robotic laboratory down to the surface.
The probe weighs 318 kg (about 700 pounds).
The Huygens Probe 'slept' for almost seven years as Cassini traveled to Saturn.
In December 2004, the probe separated from the orbiter and coasted to Titan for 22 days. Huygnes then transmitted data back to Cassini during its 2.5 hours parachute descent to Titan's surface. Although it was primarily an atmospheric probe, Huygens survived for more than 90 minutes on Titan's surface.
The probe is named for Christiaan Huygens, a 17th century Dutch astronomer who discovered the Saturn's rings and its largest moon Titan.
Cassini-Huygens Trajectory:
After its launch (15 Oct '97) and
a targeting maneuver (3 Dec '98),
Cassini went to Venus (26 Apr '98).
Then around the Sun and back to Venus (24 Jun '99).
Then back to Earth (18 Aug '99).
Then to Jupiter (30 Dec '00).
And finally to Saturn (1 Jul '04).
Initial Explorations of Phoebe (a very small moon of Saturn's),
Titan (its largest moon, with an atmosphere),
and The Rings of Saturn (F and most of A, with Encke's Division):
Initial Explorations of Mimas,
and Enceladus (small moons of Saturn's):
Phoebe, Saturn's battered little moon is an interloper to the Saturn system from the deep outer solar system,
scientists have concluded. The new findings appear in the May 5 '05 issue of the journal Nature.
"Phoebe was left behind from the solar nebula, the cloud of interstellar gas and dust from which the planets formed",
said Dr. Torrence Johnson, Cassini imaging team member at NASA’s Jet Propulsion Laboratory, Pasadena, Calif.
With the new information they have concluded that it has an outer solar system origin,
akin to Pluto and other members of the Kuiper Belt.
See Cassini-Huygens Home
(NASA-JPL Press Release 2005-071, May 6 2005).
Phoebe's orbital period is retrograde, contrary to the rotation of the planet.
For information on the Kuiper Belt, see The Search for The Kuiper Belt (in ARVAL)
For information on the moons of Saturn, see
Classic Satellites of the Solar System (in ARVAL)
Timeline:
October 15 '97: Launch
April 26 '98: First Venus Flyby
June 24 '99: Second Venus Flyby
December 30 '00: Jupiter Flyby
March 31 '01: Jupiter Observations Complete
June 11 '04: Phoebe Flyby
July 01 '04: Saturn Orbit Insertion (June 30, 10:36 PM EDT)
July 05-11 '04: Saturn in Solar conjunction (communications interruption)
December 24 '04: Huygens Probe Release over Titan
January 14 '05: Huygens Probe Descent to Titan
Scientific Instruments:
Cassini:
1) VIMS visual infrared mapping spectrometer
2) ISS imaging system
3) RADAR instrument
4) ion neutral mass spectrometer
5) plasma/radio wave spectrometer
6) plasma spectrometer
7) ultraviolet spectrometer/imager
8) magnetospheric imaging instrument
9) dual technique magnetometer
10) RF instrument subsystem
11) composite infrared spectrometer
Huygens:
1) HASI atmospheric structure instrument
2) GCMS gas chromatograph/neutral mass spectrometer
3) ACP aerosol collector/pyrolyser
4) DISR descent imager/spectral radiometer
5) SSP surface science package
6) DWE Doppler wind experiment
Information and images from:
NASA - Solar System Exploration
Cassini-Huygens Mission Home (NASA-JPL)
Cassini-Huygens: Close Encounter with Saturn (NASA)
Huygens Probe (ESA)
Hooray for Huygens! (Sky and Telescope, January 14, 2005)
Standing on the surface of Titan (Sky and Telescope, January 15, 2005)
Fly Me to the Moons (Sky and Telescope, February 11, 2005)
See the articles:
Titan's Surface Revealed (Science@NASA, July 4 '04)
Saturn Hailstorm (Science@NASA, July 9 '04)
Titan: "A World Apart" (Sky and Telescope, October 28, 2004)
Wild, Weird Titan Reveals More Secrets (Sky and Telescope, January 21, 2005)
Updated: May 7 '05
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