|By Mike Foulkes, Director of the Saturn, Uranus and Neptune Section||Thursday, 2017, September 14 – 09:18|
On 2017 September 15, one of the most successful planetary missions will come to an end, when the Cassini spacecraft plunges into Saturn’s atmosphere.
This mission to study the Saturn system (designated Cassini-Huygens) has been a joint project between NASA, the European Space Agency (ESA) and the Italian Space Agency (ISA). Earlier missions to Saturn (i.e.
Pioneer 11 plus Voyagers 1 and 2) were fly-by missions but Cassini-Huygens would be the first to go into orbit around this planet.
The mission comprised an orbiter spacecraft (designated as Cassini) and a Titan lander (designated as Huygens) which was carried on the orbiter. Cassini carried a number of payloads to study the Saturnian system in wavelengths from ultra violet to infra-red.
There were also payloads to study magnetic fields, particles, and plasma waves, a radar and a radio science subsystem. In addition, signals from the various antennas were used to conduct experiments, such as testing Einstein’s theory of relativity.
The Huygens probe carried payloads to study Titan’s atmosphere, its winds and its surface plus an imaging system.
Cassini–Huygens was launched on October 15, 1997, from Cape Canaveral by a Titan IVB/Centaur rocket. It subsequently made flybys of the Earth, Venus and Jupiter to use gravitational assist manoeuvres to reach Saturn. It made studies of Jupiter during its flyby of this planet. It was inserted into orbit around Saturn on 1 July 2004.
The planned mission duration was to be four years lasting from 2004 until 2008. However a mission extension was granted to study the planet around the time when the rings were edge-on to the Sun (the Cassini Equinox Mission). This extended from 2008 until 2010. A further mission extension was granted from 2010 until 2017 (the Cassini Solstice Mission).
A major storm occurs in Saturn’s atmosphere approximately every Saturnian year and these are sometimes designated as Great White Spots. The last one started in early December 2010 in the planet’s northern hemisphere.
and Cassini was able to follow the evolution of this storm in great detail as activity spread in a latitude band around the planet.
The source spot was shown to be a vortex and the RPWS detected SED bursts over a period greater than 250 days.
The orbiter sent back many spectacular and indeed beautiful images of the ring system showing their complex structure, including ringlets and spokes. Some interesting results occurred when Cassini imaged to rings when they were edge onto the sun. Material outside of the ring plane cast shadows onto the rings sometimes revealing small embedded satellites and other structures.
Cassini discovered a number of new satellites and was able to image many of the satellites in great detail including the almost 20 km high equatorial ridge on Iapetus.
Further the Huygens probe was deployed from Cassin on 24 December 2004 and descended through the thick atmosphere to successfully land on Titan at about 12:43 UT on 14 January 2005.
Images were generated both during the descent and from the surface.
Spacecraft sent to the Saturn system
Cassini–HuygensArtist's concept of Cassini's orbit insertion around SaturnMission typeCassini: Saturn orbiterHuygens: Titan landerOperatorCassini: NASA / JPL Huygens: ESA / ASICOSPAR ID1997-061ASATCAT no.25008Website
- 19 years, 335 days
- 13 years, 76 days at Saturn
- En route:
- 6 years, 261 days
- Prime mission:
- 3 years
- Extended missions:
- Equinox: 2 years, 62 days
- Solstice: 6 years, 205 days
- Finale: 4 months, 24 days
Spacecraft propertiesManufacturerCassini: Jet Propulsion Laboratory Huygens: Thales Alenia SpaceLaunch mass5,712 kg (12,593 lb)Dry mass2,523 kg (5,562 lb)Power~885 watts (BOL) ~670 watts (2010) ~663 watts (EOM/2017)
Start of missionLaunch dateOctober 15, 1997, 08:43:00 (1997-10-15UTC08:43) UTCRocket Titan IV(401)B B-33Launch siteCape Canaveral SLC-40
End of missionDisposalControlled entry into SaturnLast contactSeptember 15, 2017
- 11:55:39 UTC X-band telemetry
- 11:55:46 UTC S-band radio science
Orbital parametersReference systemKronocentric
Flyby of Venus (Gravity assist)Closest approachApril 26, 1998Distance283 km (176 mi)Flyby of Venus (Gravity assist)Closest approachJune 24, 1999Distance623 km (387 mi)Flyby of Earth-Moon system (Gravity assist)Closest approachAugust 18, 1999, 03:28 UTCDistance1,171 km (728 mi)Flyby of 2685 Masursky (Incidental)Closest approachJanuary 23, 2000Distance1,600,000 km (990,000 mi)Flyby of Jupiter (Gravity assist)Closest approachDecember 30, 2000Distance9,852,924 km (6,122,323 mi)Saturn orbiterOrbital insertionJuly 1, 2004, 02:48 UTCTitan landerSpacecraft componentHuygensLanding dateJanuary 14, 2005
Large Strategic Science Missions← GalileoMars Science Laboratory →
The Cassini–Huygens space-research mission (/kəˈsiːni ˈhɔɪɡənz/ kə-SEE-nee HOY-gənz), commonly called Cassini, involved a collaboration between NASA, the European Space Agency (ESA), and the Italian Space Agency (ASI) to send a probe to study the planet Saturn and its system, including its rings and natural satellites. The Flagship-class robotic spacecraft comprised both NASA's Cassini probe and ESA's Huygens lander, which landed on Saturn's largest moon, Titan. Cassini was the fourth space probe to visit Saturn and the first to enter its orbit. The two craft took their names from the astronomers Giovanni Cassini and Christiaan Huygens.
Launched aboard a Titan IVB/Centaur on October 15, 1997, Cassini was active in space for nearly 20 years, with 13 years spent orbiting Saturn and studying the planet and its system after entering orbit on July 1, 2004.
 The voyage to Saturn included flybys of Venus (April 1998 and July 1999), Earth (August 1999), the asteroid 2685 Masursky, and Jupiter (December 2000).
The mission ended on September 15, 2017, when Cassini's trajectory took it into Saturn's upper atmosphere and it burned up in order to prevent any risk of contaminating Saturn's moons, which might have offered habitable environments to stowaway terrestrial microbes on the spacecraft.
 The mission has been successful beyond expectations – NASA's Planetary Science Division Director, Jim Green, described Cassini-Huygens as a “mission of firsts”, that has revolutionized human understanding of the Saturn system, including its moons and rings, and our understanding of where life might be found in the Solar System.
Cassini's planners originally scheduled a mission of four years, from June 2004 to May 2008. The mission was extended for another two years until September 2010, branded the Cassini Equinox Mission.
The mission was extended a second and final time with the Cassini Solstice Mission, lasting another seven years until September 15, 2017, on which date Cassini was de-orbited to burn up in Saturn's upper atmosphere.
The Huygens module traveled with Cassini until its separation from the probe on December 25, 2004; Huygens landed by parachute on Titan on January 14, 2005. It returned data to Earth for around 90 minutes, using the orbiter as a relay. This was the first landing ever accomplished in the outer Solar System and the first landing on a moon other than Earth's Moon.
At the end of its mission, the Cassini spacecraft executed its “Grand Finale”: a number of risky passes through the gaps between Saturn and Saturn's inner rings.
This phase aimed to maximize Cassini's scientific outcome before the spacecraft was disposed.
 The atmospheric entry of Cassini ended the mission, but analyses of the returned data will continue for many years.
Teams from 28 countries made up the joint team responsible for designing, building, flying and collecting data from the Cassini orbiter and Huygens probe.
The mission was managed by NASA's Jet Propulsion Laboratory in the United States, where the orbiter was assembled. Huygens was developed by the European Space Research and Technology Centre.
The Centre's prime contractor, Aérospatiale of France (now Thales Alenia Space), assembled the probe with equipment and instruments supplied by many European countries (Huygens' batteries and two scientific instruments by the United States).
The Italian Space Agency (ASI) provided the Cassini orbiter's high-gain radio antenna, with the incorporation of a low-gain antenna (to ensure telecommunications with the Earth for the entire duration of the mission), a compact and lightweight radar, which also uses the high-gain antenna and serves as a synthetic-aperture radar, a radar altimeter, a radiometer, the radio science subsystem (RSS), the visible channel portion VIMS-V of VIMS spectrometer.
The VIMS infrared counterpart was provided by NASA, as well as Main Electronic Assembly, which includes electronic subassemblies provided by CNES of France.
On April 16, 2008, NASA announced a two-year extension of the funding for ground operations of this mission, at which point it was renamed the Cassini Equinox Mission. The round of funding was again extended in February 2010 with the Cassini Solstice Mission.
Huygens' explanation for the aspects of Saturn, Systema Saturnium (1659)
The mission consisted of two main elements: the ASI/NASA Cassini orbiter, named for the Italian astronomer Giovanni Domenico Cassini, discoverer of Saturn's ring divisions and four of its satellites; and the ESA-developed Huygens probe, named for the Dutch astronomer, mathematician and physicist Christiaan Huygens, discoverer of Titan.
The mission was commonly called Saturn Orbiter Titan Probe (SOTP) during gestation, both as a Mariner Mark II mission and generically.
Cassini-Huygens was a Flagship-class mission to the outer planets. The other planetary flagships include Galileo, Voyager, and Viking.
Cassini had several objectives, including:
- Determining the three-dimensional structure and dynamic behavior of the rings of Saturn.
- Determining the composition of the satellite surfaces and the geological history of each object.
- Determining the nature and origin of the dark material on Iapetus's leading hemisphere.
- Measuring the three-dimensional structure and dynamic behavior of the magnetosphere.
- Studying the dynamic behavior of Saturn's atmosphere at cloud level.
- Studying the time variability of Titan's clouds and hazes.
- Characterizing Titan's surface on a regional scale.
Cassini–Huygens was launched on October 15, 1997, from Cape Canaveral Air Force Station's Space Launch Complex 40 using a U.S. Air Force Titan IVB/Centaur rocket. The complete launcher was made up of a two-stage Titan IV booster rocket, two strap-on solid rocket engines, the Centaur upper stage, and a payload enclosure, or fairing.
The total cost of this scientific exploration mission was about US$3.26 billion, including $1.4 billion for pre-launch development, $704 million for mission operations, $54 million for tracking and $422 million for the launch vehicle. The United States contributed $2.
6 billion (80%), the ESA $500 million (15%), and the ASI $160 million (5%). However, these figures are from the press kit which was prepared in October 2000.
They do not include inflation over the course of a very long mission, nor do they include the cost of the extended missions.
The primary mission for Cassini was completed on July 30, 2008. The mission was extended to June 2010 (Cassini Equinox Mission). This studied the Saturn system in detail during the planet's equinox, which happened in August 2009.
On February 3, 2010, NASA announced another extension for Cassini, lasting 61⁄2 years until 2017, ending at the time of summer solstice in Saturn's northern hemisphere (Cassini Solstice Mission). The extension enabled another 155 revolutions around the planet, 54 flybys of Titan and 11 flybys of Enceladus.
In 2017, an encounter with Titan changed its orbit in such a way that, at closest approach to Saturn, it was only 3,000 km above the planet's cloudtops, below the inner edge of the D ring.
This sequence of “proximal orbits” ended when its final encounter with Titan sent the probe into Saturn's atmosphere to be destroyed.
Cassini-Huygens on the launch pad
Cassini–Huygens's origins date to 1982, when the European Science Foundation and the American National Academy of Sciences formed a working group to investigate future cooperative missions. Two European scientists suggested a paired Saturn Orbiter and Titan Probe as a possible joint mission. In 1983, NASA's Solar System Exploration Committee recommended the same Orbiter and Probe pair as a core NASA project. NASA and the European Space Agency (ESA) performed a joint study of the potential mission from 1984 to 1985. ESA continued with its own study in 1986, while the American astronaut Sally Ride, in her influential 1987 report NASA Leadership and America's Future in Space, also examined and approved of the Cassini mission.
While Ride's report described the Saturn orbiter and probe as a NASA solo mission, in 1988 the Associate Administrator for Space Science and Applications of NASA, Len Fisk, returned to the idea of a joint NASA and ESA mission. He wrote to his counterpart at ESA, Roger Bonnet, strongly suggesting that ESA choose the Cassini mission from the three candidates at hand and promising that NASA would commit to the mission as soon as ESA did.
Wellesley Astrophysicist Who Worked on NASA’s Cassini Mission Reflects on Its Impact
Photo provided by NASA
Since 1990, Wellesley’s Richard French has been studying Saturn as a leading team member of NASA’s Cassini mission. Today, September 15, the spacecraft that has orbited the universe’s giant ringed planet for 13 years will crash into it in a fiery (but very much planned) death, concluding the mission that NASA has called one of its most successful in the history of space exploration.
French, Wellesley’s Louise Sherwood McDowell and Sarah Frances Whiting Professor of Astrophysics and professor of astronomy, served as principal investigator for Cassini’s Radio Science Subsystem team.
Daily Shot writers caught up with French, who will be watching the grand finale live from the NASA Jet Propulsion Laboratory in California.
He reflected on this extraordinary experience, from the discovery of underground oceans on several of Saturn’s moons to the role that Wellesley played—and will continue to play—in uncovering the mysteries of our solar system.
Q: You're going to be in the Jet Propulsion Laboratory press room when the final signals come in from Cassini. What are you anticipating?
A: It will be exciting and emotional to witness the final moments of the Cassini mission—we’ll all be watching a screen showing the radio signal being received from the spacecraft a billion miles away as it plunges into Saturn.
We can predict to within a few seconds when the signal will disappear as the spacecraft begins to tumble and break apart in Saturn’s atmosphere, so there will be an agonizing sense of anticipation and inevitability as we witness the destruction of a marvelous spacecraft that has revealed so much about Saturn and the solar system.
I expect to be cheering at the many accomplishments of the mission and sad to see the end of decades of working closely with scientists and engineers around the world to coax this spacecraft into doing its best. There will be tears and cheers, for sure!
Q: What were some of the most surprising findings from the radio science experiments, for which you were principal investigator?
What did the Cassini mission tell us about Saturn and its moons?
And so Cassini has met its end. One of the most successful space missions ever launched, it revealed Saturn and its moons in glorious detail. Images beamed home from the probe showed raging hurricanes that enveloped the planet, and millions of rings that surround it.
The spacecraft dropped a lander on Titan, the largest of Saturn’s 62 known moons, marking the first touchdown on a heavenly body on the other side of the asteroid belt.
But it was observations of the tiny, icy moon Enceladus that stunned astronomers most, and transformed their views on the potential for life elsewhere in the solar system.
From the moment Cassini arrived at Saturn in 2004, its cameras and other instruments radically altered scientists’ understanding of the most distant planet visible to the naked eye. Before the mission astronomers thought Saturn, the second largest planet in the solar system and the sixth from the sun, was circled by thousands of rings. Cassini showed it was millions.
And rather than static bands of dust, the rings have a complex life of their own. Cassini saw ring matter clumping into snowballs, and being cleared by tiny moonlets, leaving propeller-shaped gaps in the rings thousands of kilometres long.
In places the rings are incredibly thin, only hundreds of metres from to top to bottom, and when nearby moons pass by, they send giant waves rippling through them.
Cassini carried a European lander named Huygens. Its destination was Titan, a world so mysterious that engineers designed the lander to touch down on both liquid and solid surfaces.
The moment came in January 2005 and, at first, Huygens appeared to have settled on a crème brûlée landscape, a brittle layer coating softer ground.
The conclusion turned out to be premature: scientists later worked out Huygens had set down on a pebble before finally coming to rest.
John Zarnecki, president of the Royal Astronomical Society, worked on the instrument Huygens used to measure Titan’s resistance to the landing. “It was the first part of Huygens to make contact and for all of 15 milliseconds we were the only thing touching Titan,” he said.
“It was the most memorable day of my professional life. Fifteen years of blood, sweat and tears and it all came down to those minutes. It was incredibly emotional.
” For Zarnecki, one consolation is that while Cassini has burned up, the defunct Huygens could remain on Titan for generations to come.
Titan turned out to be an extraordinary world. Bright, feathery methane clouds float in the hazy orange sky and pour methane rain onto a surface carved by rivers, lakes and seas, producing a landscape resembling the early Earth’s.
In the seas, scientists noticed what they called “magic islands” that come and go with time. The features are not well understood, but may be massive upwellings of nitrogen bubbles.
Meanwhile, in the upper atmosphere, Cassini found molecules known as “carbon chain anions”, precursors of complex organic molecules that ultimately form the building blocks of life.
Hundreds of Orbits From NASA’s Cassini Spacecraft In Just One GIF
After 12 years orbiting Saturn, including multiple mission extensions, the Cassini spacecraft will soon meet its doom by plummeting into the planet it has so longingly investigated.
Launched in October 1997 and arriving at Saturn seven years later, Cassini has proven the gift that keeps on giving, operating in Saturn's orbit three times longer than originally planned.
It's discovered water geysers erupting from the surface of the moon Enceladus and deposited the Huygens lander on the mysterious moon Titan to discover its vast lakes of methane.
Cassini also beamed back invaluable information about the composition and structure of Saturn, its rings, and its moons for over a decade.
But the fuel is running out, so NASA will crash the spacecraft into Saturn rather than risk it impacting one of the planet's pristine, potentially habitable moons.
On Wednesday November 30, Cassini will use a gravity assist around Titan to enter a set of 20 daring and close orbits that will fling the spacecraft around Saturn's poles, skirting the edges of the planet's outer rings and attempting to obtain particle samples from the rings along the way.
In April of next year, the spacecraft will adjust its orbit to fly in between Saturn and its rings, flying as close as 1,012 miles over the cloud tops for 22 more orbits. Finally, on September 15, 2017, at 8:07 a.m. ET, Cassini will make its final dive into the clouds of Saturn, transmitting its last bits of data as it burns up in the thick alien atmosphere.
Godspeed Cassini, and farewell.
h/t The New York Times
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