Huygens!

General physics and astronomy discussions not directly related to Celestia
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andersa
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Post #81by andersa » 15.01.2005, 16:49

fsgregs wrote:Every image of what Titan looked like on the surface, done by their graphic artists, all showed a smoggy but well lit Titan with Saturn rising on the horizon. Now, it seems they were right.

Titan's rotation is locked to Saturn, right (just as the rotation of our Moon is locked to Earth)? If so, Saturn never rises or sets anywhere on Titan; it simply hangs somewhere in the sky above half the moon, and remains below the horizon to the other half. If jestr's estimated landing site 10.6 S 169 E is correct, then Huygens landed on the remote side and we can be sure Saturn is nowhere to be found in the images returned, with or without the haze.

It remains to be seen whether the sun can be discerned in any of the images from Huygens. The probe was fitted with a side-looking imager for viewing the horizon and clouds, but I guess the sun may have been more than 60 degrees above the horizon at the landing site, maybe in the "blind spot" of Huygens. :?
Anders Andersson

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Post #82by lostfisherman » 15.01.2005, 17:15

It's possible now to listen to Huygens' descent through Titans atmosphere, although it is a "laboratory reproduction"

"This recording is a laboratory reconstruction of the sounds heard by Huygens' microphones. Several sound samples, taken at different times during the descent, are here combined together and give a realistic reproduction of what a traveller on board Huygens would have heard during one minute of the descent through Titan's atmosphere."

You will need an mp3 player.

http://www.esa.int/SPECIALS/Cassini-Huy ... Y3E_0.html
or
http://www.esa.int/SPECIALS/Cassini-Huygens/index.html
Regards, Losty

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Post #83by t00fri » 15.01.2005, 17:24

lostfisherman wrote:It's possible now to listen to Huygens' descent through Titans atmosphere, although it is a "laboratory reproduction"

"This recording is a laboratory reconstruction of the sounds heard by Huygens' microphones. Several sound samples, taken at different times during the descent, are here combined together and give a realistic reproduction of what a traveller on board Huygens would have heard during one minute of the descent through Titan's atmosphere."

You will need an mp3 player.

http://www.esa.int/SPECIALS/Cassini-Huy ... Y3E_0.html
or
http://www.esa.int/SPECIALS/Cassini-Huygens/index.html



This noise is unbelievable, one might well start shivering upon realizing that it comes from 1.2 billion km's away...

Bye Fridger

Guest

Post #84by Guest » 15.01.2005, 19:33

While I'm thrilled with the content of the images, I'm disappointed about tha quality. They look about as good as the 20+ years old Venera images. I guess it's because they need to be small in size in order to make the transfer to Cassini in time.
I hope they will go back there some time.

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Post #85by ElPelado » 15.01.2005, 23:11

Brian Short wrote: How often do launch opportunities come along for Saturn missions?


It depends: if you want to go directly to Saturn(or pass Jupiter in the midlle), you can do it almost any time....
BUT if you want to fly by many planets like Cassini did, and you want to getthere quickly... I dont really know.
BTW: did you know that if there had been a problem in the launch, they had many other launch windows for the future, even for now, but if it had been launch now, it would have taken 10 years to reach Saturn, and by that time, Saturn Rings would be parallel to the Sun, that means, no enough light to picture them...
So that tells you that you can send a mission to the outer planets almost whenever you want...
---------X---------
EL XENTENARIO
1905-2005

My page:
http://www.urielpelado.com.ar
My Gallery:
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fsgregs
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Post #86by fsgregs » 16.01.2005, 01:53

Hi Fridger and everyone:

Today, I took the liberty of adjusting the color of the default Titan surface and Titan clouds, to match the first color photo, and adjusting the atmosphere to better match the photo. Here is a screenshot from the surface, compared to the photo from Huygens

Image

If you like it, I'll upload it to Motherlode as an add-on.

Comments?

Frank

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Adirondack M
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Post #87by Adirondack » 16.01.2005, 02:11

Get your Cassini-Huygens screensaver at ESA:

http://www.esa.int/SPECIALS/Cassini-Huygens/SEMGS2XJD1E_0.html

These images of Saturn and its rings and moons were taken by the NASA/ESA/ASI Cassini-Huygens spacecraft.

Adirondack
We all live under the same sky, but we do not have the same horizon. (K. Adenauer)
The horizon of some people is a circle with the radius zero - and they call it their point of view. (A. Einstein)

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Post #88by Guest » 16.01.2005, 02:19

Titan surface movie clip:
I don??t know exactly what this is, if it is legitimate or not, but it *is* interesting... Have patience, it is a 5MB download:
http://www.mars.asu.edu/~gorelick/huygens1.gif
It is an animated gif from the 1st. landing photo. (Why it is in gif format is beyond me). But looking at it while listening to the descent sound, here:
http://esamultimedia.esa.int/images/huy ... escent.mp3

... is... Weird ...

-rthorvald

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Post #89by wcomer » 16.01.2005, 02:36

More raw data (possibly all of it) can be found here:
http://anthony.liekens.net/index.php/Main/Huygens

Also some great panarama shots there.

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Post #90by rthorvald » 16.01.2005, 02:46

Anonymous wrote:Titan surface movie

That was me, suddenly logged out.
Now, if the dark "plains" really are lakes, there has to be really monumental tides... So, if that were the case, those ice rocks on the landing photo would not survive for long? How flat is Titan, anyway?

-rthorvald

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Post #91by t00fri » 16.01.2005, 10:07

You all have seen on the NASA and ESA pages these wide
grayscale panoramas from Huygen's decent. E.g. the official
post from the ESA page:
http://www.esa.int/SPECIALS/Cassini-Huygens/index.html

The group of amateurs Walton referred to and notably Christian Waldvogel
http://anthony.liekens.net/index.php/Main/Huygens

did quite a nice job in merging the raw images cleanly
together. Starting from their grayscale result, I could not
resist mapping color from the surface photo onto it. The
result looks quite "mind-inspiring" to me:
Image

Note, this is not supposed to serve for drawing any solid
conclusions! I just found it fun to combine new information
that is not obviously incorrect ;-)

Bye Fridger

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Post #92by Juan Marino » 16.01.2005, 10:26

SOUNDS OF TITAN

1. Speeding through Titan's haze

This recording is a laboratory reconstruction of the sounds heard by Huygens' microphones. Several sound samples, taken at different times during the descent, are here combined together and give a realistic reproduction of what a traveller on board Huygens would have heard during one minute of the descent through Titan's atmosphere.
File 1 : acoustic during descent :

http://esamultimedia.esa.int/images/huygens_alien_winds_descent.mp3

2. Radar echos from Titan's surface

This recording was produced by converting into audible sounds some of the radar echoes received by Huygens during the last few kilometres of its descent onto Titan. As the probe approaches the ground, both the pitch and intensity increase. Scientists will use intensity of the echoes to speculate about the nature of the surface.
File 2 : radar conversion:

http://esamultimedia.esa.int/images/huygens_alien_winds_descent_radar.mp3

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t00fri
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Post #93by t00fri » 16.01.2005, 10:38

fsgregs wrote:Hi Fridger and everyone:

Today, I took the liberty of adjusting the color of the default
Titan surface and Titan clouds, to match the first color photo,
and adjusting the atmosphere to better match the photo.
Here is a screenshot from the surface, compared to the photo from Huygens

http://www.fsgregs.org/celestia/files/Huygens%20settings.JPG

If you like it, I'll upload it to Motherlode as an add-on.

Comments?

Frank


Frank,

yes with the new color information some next round of
approximation to reality should be possible. You might also
have noticed my own attempt in "users->t00fri's
[email protected]" from yesterday morning.

There are two issues though:

1) There was NO accurate caption yet with ESA's published
color photo of Titan's surface! We have no idea on the basis
of how many filters the color has been reconstructed. I
suppose they use at best two (i.e. not a true R G B set). So
considerable uncertainty surely remains.

On the contrary, the color imaging of Titan's apparently more yellowish
/outer haze atmosphere/ done from Cassini is most probably
much closer to an accurate visual appearance. My outer Titan
clouds in Celestia-1.3.2 where matched via computer to
Cassini's natural color imaging.

So I would not dare at present to adapt the outer haze
colors to the (rather uncertain) colors of Titans
surface, as you apparently did above.

2) To me it is entirely plausible that the surface colors appear
more reddish-orange as compared to the brighter
yellow-orange shade of Titan's outer cloud hull! The
respective physics is well understood but complex in detail
and can be carefully analyzed. Before that is done, it might
at best be justified to infer preliminary and qualitative
color-adaption of Celestia's /surface/ texture from the surface
color photo, as you did above and I tried in "users->t00fri's
[email protected]". Also, as you did as well above, the /lower/
atmosphere colors in solarsys.ssc should me matched.

An interesting exercise might be to determine the position of
the sun at the Huygens landing site from Celestia, when the
color image was taken. Then we can apply some simple
physics arguments already about a possibly more red
illumination on the surface!

You surely remember that the physics of sky colors depends
nontrivially on the size of the haze droplets, their desity, the
altitude of the atmosphere and last not least on the position
of the sun...With Grant and Spiff we had some extensive
discussions about these important effects some time ago.

Bye Fridger

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Post #94by wcomer » 16.01.2005, 18:06

The arizona data is back up and now offers the same complete set of images as on the amateur site:

There are a total of 998 images in all.

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Post #95by andersa » 17.01.2005, 01:57

rthorvald wrote:Now, if the dark "plains" really are lakes, there has to be really monumental tides... So, if that were the case, those ice rocks on the landing photo would not survive for long?
Why would the tides on Titan be particularly monumental? Note that Titan has no moon of its own, and its rotation is locked to Saturn, so there should be no substantial tides caused by gravity. There may of course be waves caused by wind (and tsunamis caused by tectonic movements), but any pebbles and rocks washed away would be replaced by other pebbles and rocks, regardless of their chemical composition.

rthorvald wrote:How flat is Titan, anyway?

I'd like to know that, too. Will Cassini be able to obtain topographic data from radar measurements over the next four years so that a detailed elevation map of Titan can be drawn?
Anders Andersson

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Post #96by Cormoran » 17.01.2005, 09:05

Correct me if I'm wrong, but does our own moon not undergo a slight rotational movement during its orbit, which results in our being able to see a bit more than just one face? (I think its called libration, but I'm not sure).

By implication, this would mean that there would be at least slight tidal effects on any hypothetical body of water.

If this is also the case with Titan, then there would be tides on any body of standing liquid.

Feel free to tell me why this would not be so.....Its 9am and I'm a little bit bleary :lol:

Cheers,

Cormoran
'...Gold planets, Platinum Planets, Soft rubber planets with lots of earthquakes....' The HitchHikers Guide to the Galaxy, Page 634784, Section 5a. Entry: Magrathea

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Post #97by danielj » 17.01.2005, 13:46

I think we don??t have yet any proof about some sort of liquid in Titan.I know we have canals and some kind of coastline.But this could something else,and the seas of methanne and/or methane could have evaporated or something like that and today Titan is a dry frigid world.I think we have still a lot of speculation...

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Post #98by Evil Dr Ganymede » 17.01.2005, 18:36

andersa wrote:Why would the tides on Titan be particularly monumental? Note that Titan has no moon of its own, and its rotation is locked to Saturn, so there should be no substantial tides caused by gravity. There may of course be waves caused by wind (and tsunamis caused by tectonic movements), but any pebbles and rocks washed away would be replaced by other pebbles and rocks, regardless of their chemical composition.


Titan DOES however have a rather eccentric orbit (eccentricity 0.02, or thereabouts), which brings it closer to and further from saturn during its orbit around the planet. That's enough to cause significant tides - i've seen values for a tidal range of up to 100m if the entire planet was covered by a world ocean of liquid. Obviously it isn't, but the tidal range would still be quite significant.

The weird thing about this is that tidal interactions should have long ago circularised the orbit - even if it had an ocean under the ice (which it probably does) this would be the case - but they haven't. Which means that either something is going on at Titan that we don't know about, or our understanding of orbital dynamics is flawed...

While Titan is in a 4:3 resonance with Hyperion, there's surely not enough mass in Hyperion to keep Titan's orbit eccentric.

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Post #99by t00fri » 17.01.2005, 19:17

An eccentricity of 0 means a circular orbit according to Kepler's equations. Titan's eccentricity 0f 0.0292 is very close to a circular orbit, as may be easily checked with Celestia: put Titan at rest and let Saturn orbit around it. Watch this from a position /othorgonal/ to the orbit plane: for all practical purposes, Saturn "encircles" Titan in a "Titano-centric system" on a circular orbit...

Bye Fridger

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Post #100by Spaceman Spiff » 17.01.2005, 19:27

There is a third reason why Titan's orbit didn't get circularised. I remember reading in the early '90's some article (no, I don't remember where) that tides acting on Titan should have completely circularised its orbit by now. The fact that it ain't implies Titan has no oceans, at best small, isolated lakes. That's why I was touting Titan to be a desert world months ago.

Those dark areas may be soggy, but I still don't think Titan has much free-standing liquid, even if I did taw a stweam!

A 100km wide lake could exist and yet cause no tidal friction to change the orbit like a global ocean, yet on Titan this lake would hardly show any tides: think of the Mediteranean Sea, which has 'no' tides.

Libration is caused by two effects: orbital eccentricity (east-west nodding) and inclination of polar axis to orbital plane (north-south nodding). Our Moon shows both (7.7?° east-west from 0.055 eccentricity, 6.5?° north-south from axial tilt). Libration for Titan would be much smaller. Any tides in open liquid would have greatest changes at four points on Titan's equator at longitudes 45?°, 135?°, 225?° and 315?°. At 180?° longitude where Huygens is, there would be a minimum in tides.

I'm not sure the change in distance of Titan from Saturn by 4% would be significant for fluid tides (the Earth's eccentricity around the sun is similar to Titan's at 0.0167, but tides don't change much because of it over the year). It's the rotating of a solid body under the peaks and troughs of tide that is noticeable.

Spiff.


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