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.
Posted on 06/27/2004 9:31:08 PM PDT by NormsRevenge
PASADENA, Calif. (AP) - Two decades and $3.3 billion in the making, an international exploration of majestic Saturn begins this month when a spacecraft slips through a gap in the shimmering rings to enter orbit. Culminating a nearly seven-year, 2.2 billion-mile journey through the solar system, the Cassini spacecraft will fire its engine Wednesday night to slow down and allow itself to be captured by Saturn.
The maneuver will inaugurate a four-year, 76-orbit tour of the giant planet and some of its 31 known moons, including huge Titan.
To scientists, Saturn and its spectacular rings are a model of the disk of gas and dust that initially surrounded the sun, and they believe Cassini will help deliver insights to the formation of the planets.
But first thing after entering orbit, Cassini will act on its best chance to photograph the rings that have entranced astronomers for centuries.
"We'll never be that close to the rings as immediately after the insertion," said Charles Elachi, director of NASA's Jet Propulsion Laboratory and team leader for Cassini's radar instrument.
Cassini, laden with a dozen instruments, also carries a probe named Huygens that will be launched into the murky organic atmosphere of Titan.
The frozen moon intrigues scientists because it may have many of the chemical compounds that existed on Earth before life began.
Named for 17th century Saturn observers Jean Dominique Cassini and Christiaan Huygens, the joint project of NASA, the European Space Agency and the Italian Space Agency dates back to proposals made in 1982.
Many of the project's 260 scientists can count years of their careers just planning the mission, building Cassini at JPL in Pasadena and getting the spacecraft out to Saturn.
"We received our letters of acceptance of being team leaders or team members almost 15 years ago," Elachi noted at a briefing this month. "So as you could imagine my colleagues have great anticipation."
Cassini has already been sending science data to Earth, including a wealth of information and sharp images from a close flyby of Saturn's strange, battered old moon Phoebe.
"For the science team this has been an extraordinarily exciting time and it's a great curtain raiser for the Saturn show that's about to start at the end of the month," JPL imaging team member Torrence Johnson said.
Cassini is 22 feet long, 13.1 feet wide and weighed nearly 12,600 pounds loaded with fuel and the probe. Too far from the sun to rely on solar panels, it uses nuclear power - radioisotope thermoelectric generators - to provide electricity.
People worried that an accident could release nuclear material protested Cassini's Oct. 15, 1997, launch from Cape Canaveral, Fla. There was more concern when Cassini made a 1999 Earth flyby, but all went as planned.
The wok-shaped Huygens probe, developed by the European Space Agency, will be released from Cassini in December and will enter Titan's atmosphere in January.
Just under 9 feet in diameter and weighing 705 pounds, its six instruments will investigate Titan's atmosphere and then its surface, if it survives the impact of landing after a 2 1/2-hour descent by parachute.
It may not find a hard surface, however, and instead splash down into liquid ethane, which would quickly shut down the probe.
The probe will radio data back to Cassini up to a maximum of 30 minutes after touchdown. By then either its batteries will have failed or Cassini will have gone over Titan's horizon.
In 2000, mission officials discovered a problem that would have prevented Cassini from receiving most of that data. The design had not accounted for the Doppler effect which will change the frequency of the transmissions as Huygens falls through the atmosphere.
Jean-Pierre Lebreton, ESA's Huygens project manager, assured reporters earlier this month that the problem was fixed. But he said testing would continue in order to increase confidence in the probe's performance.
According to Elachi, some scientists believe Titan has a "pre-biotic" environment in which there is organic, or carbon-based, chemistry but biology has not begun because of the cold - minus 290 degrees Fahrenheit.
"In a sense it will give us a past picture of our own planet before biology got started," he said.
Saturn will be some 930 million miles from Earth when Cassini arrives. Radio signals will take 84 minutes to travel each way, so the spacecraft will perform the orbit insertion on autopilot.
The complete orbit insertion command sequence is already in Cassini's computer and no further commands need be sent to the spacecraft, said Robert T. Mitchell, the Cassini program manager at JPL.
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.
Rings and Moons (above photo)
June 21, 2004
Saturn’s magnificent rings show some of their intricate structure in this image taken on May 11, 2004, by the Cassini spacecraft’s narrow angle camera. Although they appear to be solid structures, the rings are composed of billions of individual particles, each one orbiting the planet on its own path.
Satellites visible in this image: Janus (181 kilometers, or 113 miles across) above the rings, and icy Enceladus (499 kilometers, or 310 miles across) below the rings. The F ring shepherd moons Prometheus and Pandora can be seen along Saturn’s outermost F ring if the image is further contrast enhanced. The image was taken in visible light from a distance of 26.3 million kilometers (16.4 million miles) from Saturn. The image scale is 158 kilometers (98 miles) per pixel. Contrast in the image was enhanced to aid visibility.
The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the Cassini-Huygens mission for NASA's Office of Space Science, Washington, D.C. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging team is based at the Space Science Institute, Boulder, Colo.
For more information about the Cassini-Huygens mission visit, http://saturn.jpl.nasa.gov and the Cassini imaging team home page, http://ciclops.org .
Very cool.
BTW saw more info on the NASA channel about the Cassini Phoebe flyby. Phoebe is indeed an unsual 'world'.
The Cassini spacecraft has beamed back a new, more detailed image of smog-enshrouded Titan. This view represents an improvement in resolution of nearly three times over the previous Cassini image release of Titan.
The superimposed coordinate system grid in the accompanying image at right illustrates the geographical regions of the moon that are illuminated and visible, as well as the orientation of Titan. North is up and rotated 25 degrees to the left. The yellow curve marks the position of the boundary between day and night on Titan. This image shows about one quarter of Titan's surface, from 0 to 70 degrees West longitude, and just barely overlaps part of the surface shown in the previous Titan image release. Most of the visible surface in this image has not yet been shown in any Cassini image.
The image was obtained with the narrow angle camera on June 14, 2004, at a phase, or Sun-Titan-spacecraft, angle of 61 degrees and at a distance of 10.4 million kilometers (6.5 million miles) from Titan. The image scale is 62 kilometers (39 miles) per pixel. The image was magnified by a factor of two using a linear interpolation scheme. No further processing to remove the effects of the overlying atmosphere has been performed.
The observed brightness variations are real, on scales of one hundred kilometers or less. The image was obtained in the near-infrared (centered at 938 nanometers) through a polarizing filter. The combination was designed to reduce the obscuration by atmospheric haze. The haze is more transparent at 938 nanometers than at shorter wavelengths, and light of 938 nanometers wavelength is not absorbed by methane gas in Titan's atmosphere. Light at this wavelength consequently samples the surface, and the polarizer blocks out light scattered mainly by the haze. This is similar to the way a polarizer, put on the front of a lens of a hand-held camera, makes distant objects more clear on Earth.
Real Cool!!!
This artist's rendering shows the notable bright surface of icy Enceladus. In the foreground, an ice geyser can be seen projecting a jet of vapor into space. Enceladus is considered by some as the source of the E ring (which can be very faintly seen along Saturn's equatorial plane); icy geysers may be responsible for sustaining the E ring's supply of micrometer-sized particles. By David Seal
Voyager 2 obtained this high-resolution picture of Saturn's rings on August 22, 1981 when the spacecraft was 4 million km (2.5 million mi) away. Evident here are the numerous "spoke" features in the B ring; their sharp, narrow appearance suggests short formation times. Scientists think electromagnetic forces are responsible in some way for these features, but no detailed theory has been worked out.
Spokes of this nature were observed to persist at times for two or three rotations of the ring about the planet. Freshly-formed spokes seemed to revolve around the planet at the same rate as the rotation of the magnetic field and the interior of Saturn, independent of their distance from the center of Saturn. It is therefore suspected that the tiny dust grains which form the spokes are electrically charged. Older spokes, which presumably have lost their electrical charge, revolve with the underlying larger ring particles.
Nice pics. It's amazing how as with the 1st picture, there is no frame of reference and the mind naturally assumes where the equator would be. (I love instances where one can see how easily the senses can be fooled.)
Be on the look out for the Travellers Herd mothership.
The first image was taken with Cassini's narrow angle camera and is shown for comparison purposes only. The other images were taken by the visual and infrared mapping spectrometer onboard Cassini.
The infrared image of Phoebe obtained at a distance of about 16,000 km (10,000 miles) shows a large range of bright and dark features. The resolution of the image is about 4 km (2.5 miles). carbon dioxide on the surface of Phoebe is distributed globally, although it appears to be more prevalent in the darker regions of the satellite.
The existence of carbon dioxide strongly suggests that Phoebe did not originate in the asteroid belt, but rather in much colder regions of the Solar System such as the Kuiper Belt. The Kuiper Belt is a vast reservoir of small, primitive bodies beyond the orbit of Neptune. An unidentified substance also appears to be more abundant in the darker regions.
A map showing the distribution of water ice (blue), ferric iron (red), which is common in minerals on Earth and other planets, and the unidentified material (green). Water ice is associated with the brighter regions, while the other two materials are more abundant in the darker regions. "
http://www.solarviews.com/eng/phoebe.htm
Bump for God, science and nature.
Cool!
> The images show the location and distribution of water-ice, ferric iron, carbon dioxide...
Water and carbon dioxide. Hell yeah! Now all that's really needed is a source of ammonia (for nitrogen) and we can start farming these guys...
By JOHN ANTCZAK, Associated Press Writer
PASADENA, Calif. (AP) - The international Cassini spacecraft was on course to enter orbit around Saturn late Wednesday and there were no problems, mission officials said.
"We're right on track," navigation team chief Jeremy Jones told a press conference Tuesday at NASA's Jet Propulsion Laboratory.
The spacecraft was programmed to ascend through a gap between two of Saturn's rings, fire its rocket for 96 minutes to slow down, and then descend back through the ring plane.
"We have identified all the risks we could come up with," said Cassini program manager Robert Mitchell.
Mitchell called orbit insertion a "hair-graying" event, but he and other officials expressed confidence in a successful outcome based on the spacecraft's performance through nearly seven years of flight.
"This whole mission has been an incredibly smooth one to fly," said Julie Webster, the spacecraft team chief at JPL.
The $3.3 billion mission is a joint project of NASA, the European Space Agency and the Italian Space Agency.
Laden with a dozen science instruments and carrying a probe to be launched into the atmosphere of Saturn's giant moon Titan, the 12,593-pound, 22-foot-long and 13-foot-wide Cassini is the last large-scale planetary explorer in the NASA pipeline.
Too massive to be launched on a direct trajectory to Saturn, it was sent toward the inner solar system, where it received two gravity assists from Venus and one from Earth.
The Earth flyby gave Cassini enough of a boost for a December 2000 flyby of Jupiter, which in turn boosted it toward Saturn. On arrival Cassini will have traveled 2.2 billion miles.
Scientists see the Saturn system as a model of the early solar system when the sun was surrounded by a disk of material. Studying it may increase understanding of how the planets formed.
"We're about to start on a delicious smorgasbord of scientific opportunities," said Dennis Matson, the Cassini project scientist.
In December, Cassini will launch the probe, named Huygens, on a course to Titan, which has a thick atmosphere rich in nitrogen, but also containing methane.
Images taken by Cassini this month showed Titan has complex surface markings and individual bright areas.
"It's probably the most exotic object in the solar system," said Jean-Pierre Lebreton, the Huygens mission manager and scientist with the European Space Agency.
The presence of carbon molecules may mean that Titan is similar to what Earth was like more than 4 billion years ago, before life appeared, he said.
Huygens will enter Titan's atmosphere in early January, radioing findings back to Cassini as it makes a lengthy descent by parachute. Scientists don't know if Huygens will land on a hard surface or splash down into an ethane-methane ocean.
"I just hope, or maybe dream, that we are really going to see oceans on Titan," Lebreton said.
A Guide to Saturn Orbit Insertion: June 30 (All times are approximate and listed in Pacific Time)
NASA TV/webcast coverage begins at 6:30 pm.
http://www.jpl.nasa.gov/webcast/cassini/
6:10 pm Spacecraft turns so its high-gain antenna can shield the craft from particles as it crosses Saturn's ring plane.
7:36 pm Engine begins burn, which will slow spacecraft down so it can be captured by Saturn's gravity. Burn lasts approximately 96 minutes.
8:54 pm Cassini captured in Saturn orbit.
9:03 pm Closest approach to Saturn of entire mission: 19,980 kilometers (12,400 miles) from Saturn's cloud tops.
9:12-9:22 pm Engine burn ends.
9:35 pm Spacecraft begins to take pictures of Saturn's rings.
* If everything proceeds as planned, first images are expected July 1, at approximately 5 a.m.
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This is completely exciting. Pingiddy padang.
Uranus or bust!
Don't forget the 'unidentified material'!
8^)
In XANADU did Kubla Khan
A stately pleasure dome decree:
Where Alph, the sacred river, ran
Through caverns measureless to man
Down to a sunless sea.
So twice five miles of fertile ground
With walls and towers were girdled round:
And there were gardens bright with sinuous rills,
Where blossomed many an incense-bearing tree;
And here were forests ancient as the hills,
Enfolding sunny spots of greenery.
But Oh! that deep romantic chasm which slanted
Down the green hill athwart a cedarn cover!
A savage place! as holy as enchanted
As e'er beneath a waning moon was haunted
By woman wailing for her demon-lover!
And from this chasm, with ceaseless turmoil seething,
As if this earth in fast thick pants were breathing,
A mighty fountain momently was forced:
Amid whose swift half-intermitted burst
Huge fragments vaulted like rebounding hail,
Or chaffy grain beneath the thresher's flail:
And 'mid these dancing rocks at once and ever
It flung up momently the sacred river.
Five miles meandering with a mazy motion
Through wood and dale the sacred river ran,
Then reached the caverns measureless to man,
And sank in tumult to a lifeless ocean:
And 'mid this tumult Kubla heard from far
Ancestral voices prophesying war!
The shadow of the dome of pleasure
Floated midway on the waves;
Where was heard the mingled measure
From the fountain and the caves.
It was a miracle of rare device,
A sunny pleasure-dome with caves of ice!
A damsel with a dulcimer
In a vision once I saw:
It was an Abyssinian maid,
And on her dulcimer she played,
Singing of Mount Abora.
Could I revive within me
Her symphony and song,
To such a deep delight 'twould win me,
That with music loud and long,
I would build that dome in air,
That sunny dome! those caves of ice!
And all who heard would see them there,
And all who should cry, Beware! Beware!
His flashing eyes, his floating hair!
Weave a circle round him thrice,
And close your eyes with holy dread,
For he on honey-dew hath fed,
And drunk the milk of Paradise.
Samuel Taylor Coleridge
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