posted June 14, 2004 12:41 AM               

First images from the Cassini flyby of Phoebe reveal it to be a scarred, cratered outpost with a very old surface and a mysterious past, and a great deal of variation in surface brightness across its surface.

"What spectacular images," said Dr. Carolyn Porco, Cassini Imaging Team leader at the Space Science Institute in Boulder, Colo. "So sharp and clear and showing a great many geological features, large and small. It's obvious a lot of new insights into the origin of this strange body will come as a result of all this."

"What we are seeing is very neat. Phoebe is a heavily cratered body. We might be seeing one of the chunks from the formation of the solar system, 4.5 billion years ago. It's too soon to say," said Dr. Torrence Johnson, Cassini imaging team member at NASA's Jet Propulsion Laboratory, Pasadena, Calif. "It's important to see the big picture from all of the other instruments to get the global view on this tiny moon."

Dr. Gerhard Neukum, an imaging team member from Freie University in Berlin, said, "It is very interesting and quite clear that a lot of craters smaller than a kilometer are visible. This means, besides the big-ones, lots of projectiles smaller than 100 meters (328 feet) have hit Phoebe." Whether these projectiles came from outside or within the Saturn system is debatable.

There is a suspicion that Phoebe, the largest of Saturn's outer moons, might be parent to the other, much smaller retrograde outer moons that orbit Saturn.

Dr. Joseph Burns, an imaging team member and professor at Cornell University, Ithaca, N.Y. said, "Looking at those big 50 kilometers (31 mile) craters, one has to wonder whether their impact ejecta might be the other tiny moons that orbit Saturn on paths much like Phoebe's."

All planned 11 instruments operated as expected and all data was acquired. Scientists plan to use the data to create global maps of the cratered moon, and to determine Phoebe's composition, mass and density. It will take scientists several days to pour over the data to make more concrete conclusions.

Cassini came within approximately 2,068 kilometers (about 1,285 miles) of the dark moon on Friday, June 11. The spacecraft was pointing its instruments at the moon during the flyby. Several hours later it turned to point its antenna to Earth. The signal was received through the Deep Space Network antennas in Madrid, Spain and Goldstone, in California's Mojave Desert, at 7:52 a.m. PDT today. Cassini was traveling at a relative speed of 20,900 kilometers per hour (13,000 miles per hour) relative to Saturn. It's been 23 years since a spacecraft last visited Phoebe. The Voyager 2 flyby in 1981 was at a distance from 2.2 million kilometers, (about 1.4 million miles), 1,000 times farther away.

With the Phoebe accomplished, Cassini is on course for Saturn. A trajectory correction maneuver is scheduled for June 16. Cassini will conduct a critical 96-minute burn before going into orbit around Saturn on June 30 (July 1 Universal Time). During Cassini's planned four-year tour it will conduct 76 orbits around the Saturn system and execute 52 close encounters with seven of Saturn's 31 known moons.

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.

posted June 30, 2004 12:33 PM               

As for the burn -- Galileo had a 38 minute burn or something -- so while 100 minutes is certainly dicey, it's nothing JPL hasn't tested and retested (and, for that matter, done in practice).

posted July 01, 2004 01:36 AM               

quote:

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Originally posted by dtemple:
Does anyone know what type engine is being used to brake Cassini into orbit around Saturn?

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posted July 01, 2004 08:56 AM            

quote:

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Originally posted by dtemple:
Does anyone know what type engine is being used to brake Cassini into orbit around Saturn?

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The engine is a derivative of the Apollo SM RCS and LM RCS engines. The main difference is the nozzle has a higher expansion ratio now and is made from columbium with a silicide coating.

posted July 01, 2004 08:57 AM               

Cassini Spacecraft Arrives at Saturn

The international Cassini-Huygens mission has successfully entered orbit around Saturn. At 9:12 p.m. PDT on Wednesday, flight controllers received confirmation that Cassini had completed the engine burn needed to place the spacecraft into the correct orbit. This begins a four-year study of the giant planet, its majestic rings and 31 known moons.

"This is a tribute to the team at NASA and our partners at the European Space Agency and the Italian Space Agency, to accomplish this feat taking place 934 million miles [1.5 billion kilometers] away from Earth," said Dr. Ed Weiler, associate administrator for space science at NASA Headquarters, Washington, D.C. "What Cassini-Huygens will reveal during its tour of Saturn and its many moons, including Titan, will astonish scientists and the public. Everyone is invited to come along for the ride and see all this as it is happening. It truly is a voyage of discovery."

Members of the Cassini-Huygens mission at NASA's Jet Propulsion Laboratory, Pasadena, Calif., broke into cheers and high-fives as NASA's Deep Space Network confirmed receipt of the signal indicating successful entry into orbit.

"We didn't expect anything less and couldn't have asked for anything more from the spacecraft and the team," said Robert T. Mitchell, program manager for the Cassini-Huygens mission at JPL. "This speaks volumes to the tremendous team that made it all happen."

Dr. Charles Elachi, JPL director and team leader on the radar instrument onboard Cassini, said, "It feels awfully good to be in orbit around the lord of the rings. This is the result of 22 years of effort, of commitment, of ingenuity, and that's what exploration is all about."

The mission will face another dramatic challenge in December, when the spacecraft will release the piggybacked Huygens probe - provided by the European Space Agency - which will plunge through the hazy atmosphere of Saturn's largest moon, Titan.

"This was America's night. This was NASA doing it right," said Dr. David Southwood, director of scientific programs for the European Space Agency. "They really gave those of us in Europe a challenge. We've got six months to go until we land on Titan. We're just praying that everything will go as well."

Julie Webster, Cassini-Huygens spacecraft team chief, said, "The spacecraft has been an incredible joy to fly. We stand on the shoulders of people who had 40 years of experience building and designing spacecraft."

Saturn is the sixth planet from the Sun. It is the second largest planet in our solar system, after Jupiter. The planet and ring system serve as a miniature model of the disc of gas and dust surrounding our early Sun that eventually formed the planets. Detailed knowledge of the dynamics of interactions among Saturn's elaborate rings and numerous moons will provide valuable data for understanding how each of the solar system's planets evolved.

Cassini traveled nearly 3.5 billion kilometers (2.2 billion miles) to reach Saturn after its launch from Cape Canaveral Air Force Station, Fla., on Oct. 15, 1997. During Cassini's four-year mission, it will execute 52 close encounters with seven of Saturn's 31 known moons.

The first images are expected to return Thursday morning. Science measurements gathered Wednesday are the closest ever obtained of Saturn. Those measurements may reveal details of the gravitational and magnetic fields that tell scientists about Saturn's interior.

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. JPL designed, developed and assembled the Cassini orbiter.

posted July 01, 2004 03:14 PM            

Early images fascinating but sure better to come.

No sign of the 'dirty dust' on the rings in early images I've seen - which Voyager spotted? Still - early great days.

posted July 01, 2004 03:32 PM               

Alain, VTM TV was right about the passing into the gap between the rings, but it might be something to do in the 'extended' part of the mission, the speed they mentioned was their own version of 50000 mph. The Voyager spacecraft didn't pass into the rings back in the early 1980s... amazing JPL considers Cassini-Huygens to do so or dive into Saturn as Galileo did into Jupiter!

posted July 22, 2004 07:03 AM            

I expect Titan surface to look a lot like Venus surface and the plate-like layers we are seeing around Endurance crater at Mars.

posted July 22, 2004 09:38 PM               

Regards,

posted July 25, 2004 11:13 AM            

If Huygens lands successfully on either a liquid, slushy or hard surface the imagers should continue to operate for anywhere from 3 to 30 minutes. Greatest success for landed operations would be on a liquid surface. A hard surface and impact may force the lower deck science packages upwards through a honeycomb material that separates them from the upper deck equipment.

I understand imager transfer rate is about 500 bps at the 10 kilometre altitude but increases to 1000 bps at one kilometre altitude.

Spectral transfer rate is 200 bps throughout.

Other equipment aboard includes:

• HASI - Huygens Atmospheric Structure Instrument
  
• DWE - Doppler Wind Experiment
  
• GCMS - Gas Chromatograph Mass Spectrometer
  
• ACP - Aerosol Collector and Pyrolyser
  
• SSP - Surface Science Package

So, I'm pretty sure it will be 'nail-biting' stuff as Huygens begins its descent through Titan's atmosphere.

Hope this detail helps

posted July 26, 2004 12:32 PM            

The 10 km altitude is about 45 minutes from 'touchdown' with 1 km altitude about 5 minutes to touchdown from pre-mision charts I've seen.

The Descent Imager is switched on at about the 10 km altitude mark at about 45 minutes to go to touchdown.At that stage (with other data streams from other experiments) the composite bit rate is around 2.77 M bits. Prior to the DI being switched on the composite data rate was 0.96 M bits - so obviously a 'big increase'.

At the 1 km altitude (reading here from a chart) the Descent Images switch to hi bit rate and the composite bit rate is then 1 M bits. (I assume some science data switched off or not collecting to account for the fall in this? It doesn't elucidate in the tech paper on this.)

Post landing transmission falls to 0.5 M bits - assuming Huygens survives and can transmit for the full 30 minutes. I understand this 30 minute surface transmission is the maximum since the Cassini antenna will be targeted away from Titan after that time expires.

I don't know (yet) how many bits constitute a Huygen's DI image.

posted July 26, 2004 12:56 PM            

• High Resolution Imager (HRI): 160x256 pixels
  
• Medium Resolution Imager (MRI): 176x256
  
• Side Looking Imager (SLI): 128x256

posted September 09, 2004 07:26 PM               

Cassini Discovers Ring and One, Possibly Two, Objects at Saturn

Scientists examining Saturn's contorted F ring, which has baffled them since its discovery, have found one small body, possibly two, orbiting in the F ring region, and a ring of material associated with Saturn's moon Atlas.

A small object was discovered moving near the outside edge of the F ring, interior to the orbit of Saturn's moon Pandora. The object was seen by Dr. Carl Murray, imaging team member at Queen Mary, University of London, in images taken on June 21, 2004, just days before Cassini arrived at Saturn. "I noticed this barely detectable object skirting the outer part of the F ring. It was an incredible privilege to be the first person to spot it," he said. Murray's group at Queen Mary then calculated an orbit for the object.

Scientists cannot yet definitively say if the object is a moon or a temporary clump. If it is a moon, its diameter is estimated at four to five kilometers (two to three miles) and it is located 1,000 kilometers (620 miles) from the F ring, Saturn's outmost ring. It is at a distance of approximately 141,000 kilometers (86,000 miles) from the center of Saturn and within 300 kilometers (190 miles) of the orbit of the moon Pandora. The object has been provisionally named S/2004 S3.

Scientists are not sure if the object is alone. This is because of results from a search through other images that might capture the object to pin down its orbit. The search by Dr. Joseph Spitale, a planetary scientist working with team leader Dr. Carolyn Porco at the Space Science Institute in Boulder, Colo., revealed something strange. Spitale said, "When I went to look for additional images of this object to refine its orbit, I found that about five hours after first being sighted, it seemed to be orbiting interior to the F ring," said Spitale. "If this is the same object then it has an orbit that crosses the F ring, which makes it a strange object." Because of the puzzling dynamical implications of having a body that crosses the ring, the inner object sighted by Spitale is presently considered a separate object with the temporary designation S/2004 S 4. S4 is roughly the same size as S3.

In the process of examining the F ring region, Murray also detected a previously unknown ring, S/2004 1R, associated with Saturn's moon, Atlas. "We knew from Voyager that the region between the main rings and the F ring is dusty, but the role of the moons in this region was a mystery," said Murray. "It was while studying the F ring in these images that I discovered the faint ring of material. My immediate hunch was that it might be associated with the orbit of one of Saturn's moons, and after some calculation I identified Atlas as the prime suspect."

The ring is located 138,000 kilometers (86,000 miles) from the center of Saturn in the orbit of the moon Atlas, between the A ring and the F ring. The width of the ring is estimated at 300 kilometers (190 miles). The ring was first spotted in images taken after orbit insertion on July 1, 2004. There is no way of knowing yet if it extends all the way around the planet.

"We have planned many images to search the region between the A and F rings for diffuse material and new moons, which we have long expected to be there on the basis of the peculiar behavior of the F ring," said Porco. "Now we have found something but, as is usual for the F ring, what we see is perplexing."

Searches will continue for further detections of the newfound body or bodies seen in association with the F ring. If the two objects indeed turn out to be a single moon, it will bring the Saturn moon count to 34. The newfound ring adds to the growing number of narrow ringlets around Saturn.

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 Science Mission Directorate, Washington. 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. UK scientists are playing significant roles in the mission with involvement in six of the 12 instruments onboard the Cassini orbiter and two of the six instruments on the Huygens probe.

posted October 09, 2004 04:22 PM            

To my 'eyes' they appear not much better than Pioneer. The Voyager images seemed to have better 'visual quality'.

Some of the recent press images released of some of the moon's are not good images at all - nothing more than bright globes in the heavens.

Have they got a problem with the cameras or imaging mechanism? Not read anything - except that was some minor damage when passed through rings on entry into orbit around Saturn.

The non imaging science instruments though are making up with some excellent early results coming through.

posted October 25, 2004 12:47 PM            

Eagerly await the close-up images of Titan - especially the hi-res images of Huygens intended target site.

posted October 27, 2004 07:44 AM            

The images released this morning are good.

Still difficult to 'determine' the surface but (leaving aside image blotches that appear) there seems to be craters and volcanoes down there. And what looks like deposits on certain 'down-wind' sides of these 'volcanoes'.

Wouldn't be surprised if it doesn't turn out to be a more dormant variety of Io?

Come on Huygen's - you can do it - in a few weeks and lift the veil once and for all.