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Fraser
2004-Jul-05, 04:54 PM
SUMMARY: Only days after arriving at Saturn, Cassini made its first flyby of Titan, the planet's largest moon. The spacecraft only got as close as 339,000 km (210,600 miles), but that was enough to reveal surprising new features about the moon's surface. Cassini is equipped with special camera filters that allow it to peer through the thick clouds that obscure most wavelengths of light. Darker regions seem to be made up of water ice, while the lighter regions are a mixture of ice and hydrocarbons. Cassini is scheduled to make 45 flybys of Titan, getting as close as 950 km (590 miles), so the view will only get better.

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jsc248
2004-Jul-05, 07:21 PM
:D Hi All,
I think it is obvious to say that this mission is going to be one of the most exciting ever. The initial images seen from Cassini and the analysis of the returned data, suggest that this is a far more dynamic system than origonally thought. The image of Titan shown in the article clearly shows a Moon with a highly complex cloud structure. I, for one, would be extremely interested in what is driving the cloud system. Is it driven by Sunlight or is there a more techtonic/internal heat source that is providing the power. I am looking forward to the next few months with great anticipation and will be counting the hours until Huygens makes it's touchdown. What exactly will it find? Will it find a solid, liquid or sludge surface? I guess we haven't got long to wait to find out. Let's hope for a healthy descent and a long and successful mission!
jsc248.

Larissa-Maria
2004-Jul-05, 08:09 PM
Originally posted by fraser@Jul 5 2004, 04:54 PM
SUMMARY: Only days after arriving at Saturn, Cassini made its first flyby of Titan, the planet's largest moon. The spacecraft only got as close as 339,000 km (210,600 miles), but that was enough to reveal surprising new features about the moon's surface. Cassini is equipped with special camera filters that allow it to peer through the thick clouds that obscure most wavelengths of light. Darker regions seem to be made up of water ice, while the lighter regions are a mixture of ice and hydrocarbons. Cassini is scheduled to make 45 flybys of Titan, getting as close as 950 km (590 miles), so the view will only get better.

What do you think about this story? Post your comments below.
Hello!
As far as Cassini's mission to Titan is concerned, I would really like to be aware of the precise time of Hyugens-Probe deployment, before or after the 45 Cassini's flybies?

Greg
2004-Jul-06, 02:19 AM
Titan is not disappointing anyone yet. And this is just enough to whet our appetites!

Littlemews
2004-Jul-06, 02:43 AM
In the article, they mention a large quantities of oxygen at the edge of the Rings, some scientist said, it was cause by the collision of something, but what? and what actually cause this left-over oxygen in the edge of the Rings? Maybe there is a hidden planet LOL

GOURDHEAD
2004-Jul-06, 12:38 PM
In the article, they mention a large quantities of oxygen at the edge of the Rings, some scientist said, it was cause by the collision of something, but what? and what actually cause this left-over oxygen in the edge of the Rings? Maybe there is a hidden planet LOL

The oxygen comes from the disassociation of the atoms that previously made up water (98 or 99 % of the mass in the rings) and perhaps carbon dioxide. Saturn's magnetic field accelerates ions (primarily from the solar wind) which collide with the water molecules (or generate photons) with appropriate energy to separate the constituent atoms. I'm not sure they covered whether the hydrogen hung around long enough for a cloud of it to be detected. They did say that this process is eroding the rings so they will eventually disappear (unless we discover a source of replenishment).

Forget the hidden planet; there's nowhere for it to hide near Saturn that we would not have detected by now.

Higher Dimensions
2004-Jul-06, 09:53 PM
The Huygens landing spot will be pretty much chosen blindly with regard to its topography. I think the possibility of surface liquid is mostly hype. My question is, why didn't they design the plan to delay the landing until more of the 45 flybys had radar-mapped the surface? Then they could choose the site better. Of course, it can be said that leaving Huygens, about 8% of the mass, onboard for an extra couple of years would have cost maneuvering fuel.

What is the range of the radar? The articles I've read don't mention any radar for the first flyby, which was at 200,000 miles. So how many of the 45 flybys will be within radar range?

From the total of 52 flybys, if I subtract the 45 Titan flybys, it appears 7 other moons will be visited once each. Will any be visited more than once? One article said 7 other moons, another 15, and a schedule in one listed 8 other moons.

Why don't NASA sites make it easier to find the mass of spacecraft? That is true for all missions, not just this one. From articles, I have that Huygens weighs 705 pounds. Cassini + Huygens weighed 12,566 or 12,680 pounds at launch. This included over 6000 pounds of fuel--articles give no exact number. Imprecise numbers are that 1/4 of the fuel was used in an earlier long adjustment, and 1/4 in the 96-minute orbital insertion. So Cassini + Huygens now weighs 9000 pounds. In 4 years, I assume Cassini alone will weigh 5384 pounds, since one article gave that as its present mass.

The mission cost is $3.3 billion, but the U.S. pays only $2.5 B. The spacecraft + launch cost $1.4 B and operations will be $1.9 B. Europe pays 1/4 of the $3.3 B. The 1/4 is $432 M Huygens (built in France) + $160 M high gain antenna (built in Italy) + payroll of the 150 European scientists among the 260 total scientists.

imported_Elias
2004-Jul-07, 03:42 PM
The Huygens landing spot will be pretty much chosen blindly with regard to its topography. I think the possibility of surface liquid is mostly hype.

Hi. Just answer your question:

1. Huygens is a very very difficult mission. Before this flyby we had very little info on Titan. This very little info was used to design the whole mission and to design the spacecraft. There is still too much uncertainty about the conditions of Titan's atmoshpere. These conditions play an important role in the most critical part of the mission: the entry and deployment of the first parachute. Therefore, one of the main drivers to design the mission was to choose the appropriate entry path and conditions so that the probe will survive and function well in the entry. So the entry location that was chosen in the atmosphere, was chosen in order for the probe to satisfy the engineering requirments. So no landing site was chosen, just entry conditions (and other factors of course, such as comms with Cassini). The fact that the landing site is located where you see in the map, is just because the entry conditions point there

2. Even if there was a flexibility to choose a landing site, you can't just have a project team wait for a few tens of flybys (that would take years to complete), to wait for a few more years for a 2.5 hour mission. Don't forget that Huygens planning started ~20 years ago. On top of that, you would need much more money to support a project team for a few more years, to work preparing the probe. Don't just think in technical terms - some times the answer to questions is beyond technical and scientific issues

3. Of course, you are also correct about the additional mass that Cassini would have to carry, if it had to release Huygens later. Also, if you want to decide about the landing site at a later stage, you need to redesign every time (according to your decision about the day of the landing) the Cassini Orbit tour. That is a huge task! You can't just have 10-15 different orbital tours, according to what day you decide to land on Titan.

4. Coming back to the landing site, yes it would be interesting to have Huygens land on an interesting site (rather than on the pure ice, as it seems now), but don't forget that Huygens is a probe to make atmospheric studies. And in a first approximation, Titan's atmoshpere is homogenous as we are very far from the Sun and thus there are not so many temperature gradients. Wherever Huygens enters, it could give us good results not just for the local atmosphere, but also for the global atmosphere (always by making considerable assumptions)

5. As for the surface studies that Huygens will make, well the DISR imager will start operatin from around ~140 km altitude, so the field of view would cover huge areas, not just a few km wide landing site. Huygens, like Cassini will be able to see from high altitude very distinct areas (dark/bright) and in much better resolution than Cassini. When it lands... well lets hope that it can survive the impact. That would be a bonus, but don't forget. Huygens is not a lander


I hope this helps answer your first question. For the others, I 'll try to answer you to some (I don't know all of them), when I have time. :)

Fraser
2004-Jul-07, 07:27 PM
Thanks for your answers Elias. :-)

eggplant
2004-Jul-08, 01:26 AM
very thoughtful and informative info so far...
all I gotta say is
OMG!!!! repeated ad nasuem...
yo... pure water and gasoline...
any way this won't sell in/on this world today?

Guest
2004-Jul-08, 01:05 PM
Thank you for answering my first paragraph. I think your most compelling point is Point 3. I'm guessing that it says that of the 45 flybys, the flyby that releases Huygens requires a special trajectory. For some reason, this trajectory is optimized early in the 45 flybys, before Cassini radar-maps Titan. Another probable reason is that the longer you wait, the more can go wrong, so first priorities should be executed first.

The first place I looked for answers was the NASA site. If they are there, I missed them. The second place to look is media articles, which is why I'm trying to iron out their contradictions (not Universe Today articles).

I included my last paragraph, about financial matters, in case anyone is interested. It's not really a question, unless you want to correct the numbers.

Sorry that I used pounds instead of kilograms. Hope to hear further answers, in whatever units you want. Thanks for answering, Elias. (I'll start accumulating more questions to give you something to do.)

Higher Dimensions
2004-Jul-08, 01:08 PM
Whoops, that Guest was me. I didn't know I could post without it making me log in.