Cassini and Iapetus distance when photo taken?

[zecg]

According to this, Cassini was 71,978 km far from Iapetus when he snapped that photo (31.12.2004.)- but in Celestia's simulation, distance for that day ranged from 450,000 - 408,000 km, which is about six times as much. At least it seems to be correct in the sense that distance increases after 31. 12.

It may just be a case of me being naive - how precise is Celestia in these matters usually?

[jestr]

I'm guessing that it is innaccuracies in the moon orbit definitions,as I have just downloaded the latest xyz version of Cassini's orbit (via Nasa's Telnet) ,and it still has a distance of 120000km,from Iapetus,even with 5min interval steps in Cassinis orbit.Checking further ahead,Cassini flybys of Titan are noticeably inaccurate-flying through Titan 3 times in 2006,and at least 8 times in 2007.Of course its always possible to create your own xyz orbit definitions for the moons (again using data from Horizons Telnet service) but these are only practicle for short periods of time,Jestr

[zecg]

Please, do share this new Cassini - 120.000 km seems much more precise. Does it also include Huygens after deployment? Just slap the block of text here in this thread - thanks in advance.

[jestr]

Hi Zecg,I will upload the new xyz file to the Motherlode in the next couple of days,together with the Huygens one (I have also made models for the different stages of Huygens descent to the surface of Titan),but I have been holding off until the actual event occurs (in case it all goes horribly wrong).I have had to adjust both files though, using Toti's excellent XYZ builder script,to avoid Cassini diving into Titan.The new Cassini xyz file is a little bit big (2.6Mb)to post here and runs to near 27000 lines.Will post the link here when it is available,Jestr

[jestr]

OK,you can now download my new Cassini XYZ file as part of the following addon
http://www.celestiamotherlode.net/creators/jestr/Cassini_Huygens_Landed_CMOD.zip
Just unzip to your 'extras' folder,but make sure there are no other Cassini addons already in your 'extras' folder as it may cause problems.This includes Huygens descent to the surface of Titan,although the xyz is a bit wobbly near the surface (I dont think there is much I can do to change this,but if anyone can come up with a better one let me know).The Cassini xyz is made from data Ive downloaded over the past week from Horizons Telnet service,although because of inaccuracies in the moon orbit definitions I have altered it a little (using Toti's XYZ Builder script) to stop Cassini crashing through Titan.The only downside is that JonR's excellent script now places you in different viewpoints to where Cassini is but this isnt difficult to correct,hope everyuthing goes well with the real Titan descent now,Jestr

[fsgregs]

Dear Jestr:

What a great add-on. Your talent keeps dazzling us all. I love the add-on and want to incorporate this into my educational activities ASAP, if that's OK.

However, I may or may not have the correct Titan ssc file. I am using the default Titan ssc file, but when I ran your add-on in 1.3.2, here is what happened:

A) Huygens began to display the glowing shock wave cloud at an altitude of 3600 km from Titan. I don't know how high Titan's atmosphere would extend for real, but 3600 km seems way too high to begin encountering enough atmospheric drag to create a shock wave.

B) Huygen's parachute deployed at an altitude of 2720 km. That again seems way too high for chute deployment, but maybe I'm wrong.

C) Parachute deployment was at 9:09:52, with Huygens reaching 0 meters in altitude at 11:34:40. That is close to 2 1/2 hours. I have not been able to determine how long the chute drop should be, but would it be that long?

D) Unfortunately, as I followed the chute probe down, it passed -22 km into Titan (under the surface) before it finally disappeared.

E) The Huygens on land model is not close to the location where the parachuted probe came down, at least on my system. They seem to be many km apart.

Are you getting any of these things too, or is something wrong with the add-on on my system?

Frank

[t00fri]

Indeed, Jestr,

so we are all set due to your nice work...

Bye Fridger

[Cham]

t00fri, apparently, from your picture above, you have a texture problem ! The model should appears all mapped with nice textures !

[t00fri]

t00fri, apparently, from your picture above, you have a texture problem ! The model should appears all mapped with nice textures !

Ah, thanks, I was wondering already. Probably, there was something in the way. We'll find it. Sure.

Bye Fridger

[jestr]

Yes,sure Frank you can use this addon,I have tried many different ways to correct the altitudes and,position of Huygens to match the correct altitudes but I'm not sure if the XYZ file can be accurate enough to stop this please feel free to improve it if you like,Jestr
PS heres a sketch I based my descent on with the figures to aim for

[t00fri]

t00fri, apparently, from your picture above,
you have a texture problem ! The model should appears all
mapped with nice textures !

It turns out that there is a slight problem with Jestr's beautiful
add-on under Linux. I installed it under Win XP in the extras
folder with no problems. Below, are a few dramatic shots
from the Win XP rendering.

Under Linux-KDE, I did exactly do the same: freshly compiled
Celestia, no add-ons, and Jestr's add-on unpacked in 'extras'.
The result is that the textures were NOT found, while the
cmod files and the xyz files were correctly used. I keep
searching...

Bye Fridger

[Christophe]

Fridger, how can you have missed something so obvious? Just activate the console!

The fix is to run the following in the textures/medres directory:

Code: Select all

for f in * ; do mv $f `echo $f | tr a-z A-Z` ; done

Beautiful work by the way Jestr.

[t00fri]

Fridger, how can you have missed something so obvious? Just activate the console!

The fix is to run the following in the textures/medres directory:

Code: Select all

for f in * ; do mv $f `echo $f | tr a-z A-Z` ; done

Beautiful work by the way Jestr.

Shame on me and on every potential Linux user who did not immediately think of typing into the console

Code: Select all

for f in * ; do mv $f `echo $f | tr a-z A-Z` ; done

when trying to start Jestr's add-on...



But fact is that this is a BUG....

Bye Fridger

PS: Now indeed things are fine also in Linux...

[Christophe]

I agree it is a bug, but a difficult one to tackle.

Almost every add-on has this problem. The best solution I can see is that at each start-up Celestia renames all files in the textures directories to all lower case and then before opening a texture file put it to all lower case aswell.

Of course we can always run into all kinds of wierd problems when someone tries to use non ASCII-7bit characters for example (anyone feels like implementing a unicode collation algorithm? How does Windows handles this?) or if some wierdo Unix user tries to use two textures with the same name but different case. Not to mention people installing add-ons as root in their system wide extras directory and then running Celestia as a normal user.

Oh, and

Code: Select all

for f in * ; do mv $f $(tr a-z A-Z <<< $f) ; done

works too ;-)

[t00fri]

I agree it is a bug, but a difficult one to tackle.

Almost every add-on has this problem.

Well since I /very/ rarely use anybody's add-ons (except my own ones), I was totally naive in this respect

Bye Fridger