Scientists are preparing to bombard the invention in the last six months of the Cassini mission to Saturn, when robot powered by plutonium ram repeatedly through unexplored space in the famous rings of the planet, after a damaging penetration into the atmosphere in September.
The last dramatic action has been in the works since 2010, when NASA formally approved the plan, using the overflights Saturno Titán month periodic burns and thrusters to change the shape of the orbit of Cassini that surround the planet.
The Cassini mission will end with a dip, September 15, in the atmosphere of hydrogen-helium Saturn after a series of 22 weeks close orbit passing between more ice planet and rings, with the clouds. The robotic spacecraft will launch the last stage of the mission--dubbed the "grand final", with a flyby of the Moon of Saturno Titán on April 22, followed by the first dive through the gap in the ring about four days later.
"In many ways, the grand finale of Cassini is the new mission," said Linda Spilker, Cassini project in Pasadena, California jet propulsion laboratory scientist. "We measure the magnetic field in search of magnetic Dynamo, and try and find out why there are so few, or maybe not, Saturn probe, the angle between the magnetic field axis and the axis of the arrival of Saturn. What happened there? "
Notes from the scientific research from April to September is very strong, but Cassini has withstood the first trip inside the ring."Only feat sailing and our path through the space between the ring and the planet, which itself seems a triumph of engineering, engineering", said Earl Maize, Cassini at JPL project manager.This is the story that played out in the meeting room, notes and slides in presentation between the scientists and engineers who work in many space missions. Scientists who are hungry for a new paragraph press for more, while engineers warn of risks and hazards that could overload a spacecraft or instrument.
Cassini has last action team brave members of the mission who are struggling with the same dilemma of balance: the data are more or less risk?
But the calculation has been changed by Cassini, which in the last six months 13-year Odyssey around Saturn. While the managers say they want to avoid any stupid with the spacecraft's mission, reducing the time horizon have officials who are willing to take more risks. The ship will make the first step through the 1,500-mile wide (2,400 kilometers) between the rings of Saturn and the atmosphere with high gain dish antenna pointing forward, blocking sensitive orbiter electronics, computers and scientific sensors from collisions with ice and dust that can fill the area.
Space ships have last any time through the gap, and even though their pictures Show traces of powder or ice in the trajectory of Cassini, those officials could not be secure from threatening. Cassini will move so quickly that a break-for the above with small grains can cause damage to the disaster.
"The inner Ring is called the D-ring, and slowly a little faded in areas that we can't see," said corn. "Let's go to the areas where you can't see. We have a very good model of the ring, and believe that we will be safe, however, they will be five cases in which we are going to hide behind high gain antenna as we go through the ring just because we're getting close. "
High gain antenna in a position called "ram", pointing to the direction of Cassini in travel, travel first through a gap in the ring, provides an opportunity to assess how much the ice drivers of Earth and dust really exist.Cassini will fly through space in places that are a little different in each orbit. In four steps from May to July, the ship will be closer to the ring D and engineers will rotate with Cassini again puts the antenna in a position of ram in orbit.
"There is a greater possibility and that we receive often, collisions of powder," corn said in an interview with spaceflight now. "We will try to be careful, but at the same time there is that possibility. "If we get surprised, and we have more dust than we thought, then it is probably hidden behind high gain antenna is much more often," said corn.
But officials of the major changes.
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Cassini plans go ship cut 10 weeks of scientific observations, and for the grand finale of the summer campaign is planned in detail. "Science is all carefully integrated and coordinated between all the instruments, and if we start moving if we hide behind high gain (antenna), and if not, then that can be very disturbing," said corn.
Another danger waiting for Cassini to another edge of the gap, where the top layer of the atmosphere of Saturn is Flip on the orbiter. Aerodynamic forces a little bit maybe too strong for Cassini, a set of reaction wheel mass designed to maintain the momentum of spin art. To end the Mission's journey through the five ring gap ground controllers Activate thrusters for rockets firing probe,
hydrazine to prevent aerodynamic forces it put Cassini is falling. The Cassini project, first conceived in the 1980s, cost nearly $4 trillion from beginning to end. Cassini was launched in October 1997 from Cape Canaveral aboard the Titan 4 rocket flew by Venus and Jupiter and arrived at Saturn in July 2004, becoming the first space probe to enter orbit there.
The European Huygens probe falls the orbiter to land on the surface of Titan, Saturn's largest moon, January 2005. Since then, Cassini Saturn circle has more than 260 times, put together a detailed picture of the atmosphere of Saturn's polar vortex and mysterious hexagonal, exploring its rings in detail and observed 49 of 62 known moons of Saturn up close flybys with long distance.
Cassini was originally scheduled to collect data four years after it arrived in orbit around Saturn, but NASA extended the mission, the probe found that the planet and moons that demands a deeper research.Titan hosts some characteristics similar to the Earth, as the thick atmosphere, rivers, lakes, and rain, but the liquid on the surface of Titan is not water. This is a mixture of Ethane, methane and other hydrocarbons.
313 miles in diameter Saturno Encélado (504-kilometer) Moon has global sea water buried under ice-discovery made by scientists with Cassini. Enceladus eruptions in South Pole spray gas, dust and organic matter in space, and Cassini has a sample in a series of jet overflights.
Accumulated knowledge has increased, with each of the hundreds of Cassini's encounter with Saturn's moon, adding another piece of the puzzle. Meanwhile, NASA as other rover Curiosity and new horizons mission make news when they landed on Mars and Pluto's face unveiled for the first time.
"We always thought that we should be on the front page every day," said Cassini's legacy of corn. "I think that it has reached maturity in the scientific community. This is a machine disocvery. "
He cited the decision by NASA last year to solicit proposals for new missions to Saturn's moon Titan and Enceladus. This time the space agency has not confirmed the Saturn after Cassini mission.
"The fact that he really has created the world's oceans program and they allow the proposed new mission to Titan and Enceladus, which is in us," said corn. "They are the invention of Cassini who opened this new set of horizon, which not only some of the world's seas, but there may be many and they don't have to be great." Take A Look At Enceladus! "
The moon may also have to hide it underground, and the rest of the motley crew of Saturn's moons have their own stories. There is Hyperion, which turned out to be unexpected, less dense than water and resembling a sponge or honeycomb '. Mimas, Saturn's moon, most likely it consists almost entirely of water ice, and the surface is marked with a giant crater, get a nickname as the "death star."
Two small cup-shaped moons pan and Atlas mountains, have shared their equators. Scientists believe that objects, each about the width of a large city, which collects the dust and ice grains of Saturn's orbit that is already near the planet's rings.
Cassini is now getting some of the best views of Saturn's moons.
The spacecraft swung into orbit last November that touches the outer edge of the a ring of Saturn, Titan for the meeting in April, when Cassini crosses in the ring. Orbit "grazing ring" has produced a detailed look of the ring structure, as well as the many moons of Saturn are carving a path between individual rings.NASA released pictures Thursday revealing the form of bread, drawing comparisons to ravioli or walnuts. In January, Cassini captures breathtaking views of 5 miles (8 kilometers) wide Daphnis, who plows through a gap of 26 miles (42 kilometers) between the rings of Saturn, gravity is weak make waves in layers around the Ring.
Next month, Cassini will closely observe some interesting features in the blades called the rings of Saturn. Scientists believe that the riots, named for the famous aviator, created by small moonlets looks so small 300 feet or 100 meters, the ring is embedded. The spacecraft will collect some of the best pictures of the propeller's mission in the coming weeks. Saturn's polar Aurora, environmental dust around the ring and imaging in the long term the Moon Tethys and Enceladus are also on tap. Cassini gets a closer view of the Atlas, the shape of the cup double for the pot and take a picture of in the shadow of Saturn the planet with rings that are illuminated by the Sun, allows scientists to produce a mosaic of faint ring components.
Then came the last meeting of the mission with the Titans on 22 April. Your Moon gravitational Slingshot Cassini near Saturn than any spacecraft in history, in the egg-shaped orbit with a high point of the ring and Threading a low point between the ring and the Saturn's cloud tops.
Researchers are eager to close to Saturn, although the end of the mission would be "an emotional moment", said corn.He said most of the Cassini team members "I think that you have landed on one of the best missions that NASA has every flown."
"It is a step and end time-exact time-has been a great trip, and I think that all the teams should be proud of their achievements," corn said. "As with any good thing to stop, you don't want to do it, but we understand why." Cassini has tripled the length of their stay at Saturn and now running low on fuel."This is more than 7 years since its launch and was at Saturn in 12.0" said corn. "Spacecraft shows its age, in some cases."
Instruments, Cassini Plasma spectrometer, stopped work in 2012, and the spacecraft was working on a backup set of rocket dikompress. "The reaction Wheel, which we use to correct our attitude control, is a maniac but continue to operate." It's something like my knee in the morning, joking corn.
But the majority of the spacecraft systems are still healthy.
"Considering his age and the amount of stress has been, is doing well," said corn. So why send to Cassini in a suicide mission? Officials are concerned that if Cassini died before falling into Saturn, a ship could plow on Titan or Enceladus, months of contamination with a toxic fuel, metal alloys and microbes of the Earth. "In a sense, Cassini has become a victim of its own success," said corn. "We have found this Prebiotik world, almost demands that we don't pollute, so we must be doing something reasonable with the spacecraft."
A shipwreck with Cassini discovery can launch any future life in months in doubt.
"Cassini in room temperature," said corn. "Our Electronics does not run right around 75 degrees Fahrenheit. For microbial resistant, it is convenient as you can, so you really don't want to leave around Saturn. " Sailors plotted the trajectory this summer in the novel ring nearly a decade ago, and NASA is placed in a bold plan after considering a collision with one of the Cassini Saturn is smaller, less habitable Moon or send a ship fly by Uranus, Neptune, Jupiter, or confuse the object of Centaur, a cross between an asteroid and a comet.
"Voyage to Uranus is something like 30 years for a quick flyby", remember Spilker.
A joint study by JPL officials and engineers from Purdue University in 2009 to identify one way send to Cassini through the rings with a thrust of gravity of Titan. "It's really a no-brainer at this point," Spilker said. "The opportunity to enter into that gap, not only for scientists but for the rings of Saturn, scientists are too much to let it go."
"Saturn is still so attractive that we chose to use the last ounce of fuel in spacecraft to explore that system," said corn. NASA considers the pioneer 11 flyby probe addresses through a gap between two sections of the a ring of Saturn in 1979. Any body think about the Voyager probe through the Guide ring called the Cassini Division in the 1980s, but the administrators choosing flights further than security issues. Cassini will pass through even close to Saturn than proposed in the Mission of Pioneer 11 and Voyager. Corn said there was little possibility that Cassini can run out of fuel before September 15, but the reaction wheels could keep the Office of the special room to complete the bulk of planned science campaign this summer.
But once Cassini jumped into the ring next month, his career will naturally to Saturn in September, even if the fault of the vessel ran out of fuel and crashes into a cloud of icy debris that is unexpected.
"There are very few prospects we really ran out of gas and stopped sputtering," said corn. "It was just how we're going to get." Spilker says scientists will measure the gravitational field of the best Saturn never analyzed radio signals between Cassini and Earth to see how much they are distorted by the gravity of the planet.
"We hope to measure the size of the Rocky base on Saturn," Spilker said on February 22, in a presentation to the group evaluation of NASA'S outer planets. "And this is the core of an interesting Rocky material that eventually formed Saturn." We'll see in also tried to measure the speed of rotation of the internal. " Cassini will near Saturn in its field of gravity with precision to determine the depth of the wind penetrates deep into the planet's atmosphere.
"It could be anywhere from 300 to 3,000 kilometers (186 to 1,860 miles) deep, and irregularities in the gravitational field will give the depth of the wind," Spilker said. The grand finale of Cassini in orbit similar to elliptical turns out NASA'S Juno spacecraft is now exploring Jupiter. Spilker said information about the interior structure of Saturn in the next few months will be compared with data from Jupiter obtained by Juno.
After the orbiter jumped into rings, scientists will be able to separate the mass of material in the rings of Saturn and yes same. Spilker says that the uncertainty in the mass of the rings would be reduced to about 5 percent, producing important clues about its origins.
"That will tell if the rings were less great," says Spilker. "There are some signs that it could be true, (in terms of) young, might formed rings broke months or a comet that came too close to Saturn."
"If they are larger, then there is a possibility that could have formed at the same time as Saturn, not given, but it could have been big enough to survive the bombing became a micrometeoroid is still there to this day," Spilker said. Cassini also showed plasma hid between Saturn and rings, weak on the planet's radiation field polls. If there is a ring of microscopic particles in cosmic dust of space flight path Analyzer, Cassini scooping the ice grains and directly measure the composition.
"We know that the ring is 99 percent water ice," Spilker said. "But if 1 percent or constituents as ice cream?" From iron? Silicate? Organic ingredients? Tholins? Mix? We will get the opportunity to directly measure. " On the last step of the five missions in August and September, Cassini will be so low that the upper layers of the atmosphere, tell the ground team on the molecules that form the outer layer of the building Saturn be cleared up if the same.
"In the last, we're deep enough such that truly defend You point towards the ground as possible, high gain antennas," Spilker said. The mass spectrometer Cassini will collect data "there" condition in the reading of the mood and the pipe to the ground in real time, but with a delay of nearly 90 minutes because of the distance of Saturn, in the storage of measurements on the recorder for playback later.
"Cassini will provide science data until the last minute of their lives," said corn.
The antenna of the orbiter can downlink information around 140 kilobits per second. On speed, it takes 10-20 seconds to transmit pictures, said corn, limiting the possibility of final image during penetration. "Appointing is not very suitable for still images, even though we are still playing with the idea of one more time," said corn. "Why not? If we can sweep the camera through a ring while we are going to be spectacular. "
Control the spacecraft's thrusters will shoot in a hurry to maintain stable probe as often as possible as a thick water Cassini interesting sequence. It will fall to the Cassini to Saturn at a speed of about 35 mph or 78,000 kilometers per second. "Because we are a sampling of the atmosphere of Saturn, while Cassini can point to the Earth, we will send the data back to science," said corn. "What is happening is that the atmosphere finally pushed to the point where it can't hold You pointed to the antenna, and it will probably be destroyed a few tens of seconds later".
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