Scenario ISS state vectors

[Wolf]

Is there a way (or a source on the web) to get the ISS state vectors for a specific time (in the past or future)?
Let's say for example I want to create a launch scenario for an STS mission (or any other mission to the ISS, like a CRS or Soyuz, etc.). In order to be realistic I need to know what was/will be the exact ISS position at time of launch. I could not find any source providing these datas...

 

[Star Voyager]

Wolfram Alpha is actually a big help for me, and does pretty much what you're looking for.

 

[Chode]

try here:

http://spaceflight.nasa.gov/realdata/sightings/SSapplications/Post/JavaSSOP/orbit/ISS/SVPOST.html

 

[Wolf]

try here:

http://spaceflight.nasa.gov/realdata/sightings/SSapplications/Post/JavaSSOP/orbit/ISS/SVPOST.html

This just give you the ISS realtime datas though. Does not help me if I need to know the ISS position at a certain date-time in the past or future months/years...

 

[boogabooga]

What you are looking for is NORAD TLE (two-line element) data sets.

You can use this add-on to import a TLE into Orbiter state vectors:
[ame="http://www.orbithangar.com/searchid.php?ID=2617"]Scenario Editor TLE[/ame]


Celestrak has a historical archive, but it looks like t only goes from 1998-2004.
https://celestrak.com/NORAD/archives/

Seems like you would need to contact the admin there to see what happened to the rest.
https://celestrak.com/NORAD/archives/request.asp


You can use the latest ISS TLE set to predict its position in the future. However, it will only be accurate for a few weeks, at most. The ISS maneuvers around every so often and those aren't going to be known too far ahead of time.

 

[SolarLiner]

One way to do it would be to get TLE data for the ISS, create orbital elements from it, then propagate to the time you want.

I made myself a TLE to Orbiter Scenario app as a demo of my AOSP project I was once doing, which you can find here: https://dl.dropboxusercontent.com/u/98670603/Orbiter/devs/dl/TLEtoOrbiter.zip

Feed it a TLE URL and an output scenario and it will create spacecrafts for all TLE entries, after you gave it for each craft its corresponding class.
You can also output a text file and it will generate the ELEMENTS line for all the entries.
You can now take them into Orbiter and propagate it yourself to the desired time.

(Apparently there's an exception thrown where the program doesn't recognize the URL you feed it, even if it is correct; the code is 2 years old and at the time I was young an innocent, it is quite a bit clumsy :lol: )

You can get TLE data for the ISS (and other stations) here: http://www.celestrak.com/NORAD/elements/stations.txt

 

[Wolf]

You can use this add-on to import a TLE into Orbiter state vectors:
Scenario Editor TLE

Is it working with Orbiter 2010P1? the "Load TLE" button does not appear on the state vectors tab of the scenario editor...

 

[DaveS]

Is it working with Orbiter 2010P1? the "Load TLE" button does not appear on the state vectors tab of the scenario editor...

You need to set the reference frame to "Ref. equator (fixed)" before the Load TLE button becomes active.

 

[Wolf]

You need to set the reference frame to "Ref. equator (fixed)" before the Load TLE button becomes active.

Did it but the button is not there

 

[DaveS]

Did it but the button is not there

You did activate ScnEditorTLE in the Modules tab did you? It doesn't overwrite the default ScnEditor but rather is its own stand-alone module.

 

[Wolf]

You did activate ScnEditorTLE in the Modules tab did you? It doesn't overwrite the default ScnEditor but rather is its own stand-alone module.

Did everything as instructed in the doc attached and module activated...

 

[DaveS]

Did everything as instructed in the doc attached and module activated...

Do you have both ScnEditor and ScnEditorTLE activated at the same time? Then deactivate ScnEditor as you don't need it as ScnEditorTLE is just the same thing with TLE import added.

 

[Wolf]

Do you have both ScnEditor and ScnEditorTLE activated at the same time? Then deactivate ScnEditor as you don't need it as ScnEditorTLE is just the same thing with TLE import added.

ok I ll try it. thanks

That was the problem: deselected ScnEditor and now it works: from the doc though one thing is not clear to me: how do I upload the desired TLE? Do I need to paste and copy the state vectors in a text file or something, or do I have to get it directly from the Celesrtack NORAD website? or what...

 

[DaveS]

ok I ll try it. thanks

That was the problem: deselected ScnEditor and now it works: from the doc though one thing is not clear to me: how do I upload the desired TLE? Do I need to paste and copy the state vectors in a text file or something, or do I have to get it directly from the Celesrtack NORAD website? or what...

You need to obtain the appropriate TLE set from whatever source you desire then put it (only one TLE set) in a txt file and save it. Then you use the TLE Scenario Editor to load that TLE set by clicking on the Load TLE button.

 

[Wolf]

This is what I ve done: took a single set (two line) of the ISS state vectors and pasted in a txt file, then tried to upload them in the TLEscnEditor but got the message "wrong TLE file"... I must be missing something..

 

[boogabooga]

You will load a txt file from somewhere on your hard drive.

One TLE per text file, and you must include the header line. Here is an example:

ISS (ZARYA)             
1 25544U 98067A   15061.96628306  .00018788  00000-0  28110-3 0  9990
2 25544  51.6449 254.5669 0008223  63.1956  89.1571 15.54994116931507

 

[Donamy]

Today's ISS TLE's

ISS (ZARYA)
1 25544U 98067A   15161.91278752  .00014896  00000-0  22259-3 0  9996
2 25544 051.6439 115.3593 0004556 036.1265 003.4508 15.55245757947062

:ninja:

 

[Wolf]

Thanks guys, I thought the header was not required and initially did not paste it in the txt file.

I made a test: took the TLE of today at 12.00 UTC and copied them in Scenario EditorTLE. The ISS orbit seems very close to the real one but some of the values are not really matching (see pic 1 below).
The Argument of Periapsis for example seems a lot different (Orbiter is 64.97 degrees where the real one is 48.79 degrees). Also Ecc have slightly different values (but I guess that's acceptable since it is just around 0.0005)

Comparing the state vectors also gives me some different datas (pic 2 below) both in position and velocity on the 3 axes.

Are these discrepancies normal considering maybe Orbiter limits?

View attachment 13755

View attachment 13756

PS sorry the ref. frame in pic 2 is the ecliptic instead of the equator (still in Equ rthe values are quite different)

Also there may be something wrong in the way I proceed: what I do is launch an ISS scenario, change the date to match with the TLE date that I am taking from the NASA website (i.e: June 17 2015 at 12:00 UTC), pause the sim and then paste the TLE in Orbiter using the ScnEditorTLE. Maybe this is not the correct procedure..

 

[boogabooga]

Also there may be something wrong in the way I proceed: what I do is launch an ISS scenario, change the date to match with the TLE date that I am taking from the NASA website (i.e: June 17 2015 at 12:00 UTC), pause the sim and then paste the TLE in Orbiter using the ScnEditorTLE. Maybe this is not the correct procedure..

Sounds good. Did you hit apply?

 

[Wolf]

Sounds good. Did you hit apply?

Yeap