ISS

[jim]

Sorry, my english isn't realy good but i hope someone unterstand me.

This is my first time posting here so i want thank for great program.

Ok i found that picture of ISS on NASA-page over Rio Negro and compared it with celestia 1.2.5 pre7.



[img]http://www.angelfire.com/de3/jimpage/images/rio_negro.jpg"[/img]

What can you see but the model of ISS isn't correct?
There is a time difference (photo time 14:43) of 26 minutes. (I think time
on photo is right.)
The orientation of ISS isn't correct. You see on the photo the soyuz on top
of ISS but on celestia picture it looks toward you without solarpanels. I
don't now how do use the parameters in solarsys to correct them.

If you want see a good model of ISS the best i found at http://www.parallelgraphics.com/l2/vrml/cosmos/
but it can't be downloaded.[/img]

[selden]

Jim,

The orbit of the ISS varies a lot with time. There are many forces acting on it that Celestia knows nothing about. The orbital elements that Celestia has in solarsys.ssc were right long ago, but not now.

To see where the ISS is now, you can visit the page
http://spaceflight.nasa.gov/realdata/tracking/
At the instant that I'm looking at it, it shows that the ISS is heading south over the west coast of Africa. Celestia shows it over the western Pacific -- not even close.

In principle, one can update the parameters that Celestia uses from the orbital parameters shown on the Web page http://www.hq.nasa.gov/osf/station/viewing/issvis.html
but they aren't in the format that Celestia needs. I seem to recall Chris mentioning that he hoped to add the ability to use the "Two-Line Keplerian Orbital Elements" that they have on that page, but I don't think that's happened yet.

Sorry.

[granthutchison]

Jim:
Matt McIrvin posted a correction to the solarsys.ssc file which at least gets the ISS into the correct orientation relative to its orbit, but his code was for version 1.2.4. In Celestia 1.2.5 pre7 you should add the following to the ISS definition.

Code: Select all

Obliquity 51.5684 # should be same as orbit inclination
RotationOffset 90 # to get the vertical axis right
EquatorAscendingNode 343.1518 # should be same as long. of ascending node


Grant