Incorrect position of ISS

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Forum » SpaceEngine » Mods and Addons » Incorrect position of ISS

Incorrect position of ISS

Orcinus

Date: Sunday, 30.11.2014, 22:57 | Message # 1

Observer

Group: Newbies

Germany

Messages: 9

Status: Offline

Hey,

i try to add the ISS on its real orbit. I created an entry in the spacecraft.cfg.

I used the offcial TLE for the 30/11/14:

Code

ISS
1 25544U 98067A 14334.49688418 .00016717 00000-0 10270-3 0 9044
2 25544 51.6469 355.0173 0007436 80.4977 279.7014 15.51657324 37135

The missing values for SpaceEngine I determined with http://www.satellite-calculations.com/TLETracker/SatTracker.htm.
The Period I calculated with the formular: 1 / (365 * rev/day)
The SemiMajorAxis I calculated with: Semi-Mayor-Axis (km) / 149597870.7

This is the entry in spacecraft.cfg:

Code

Spacecraft    "International Space Station"
{
  Model       "addons/Real/ISS_final.sss"
  SystemID    "-1.-1.-1.-1.-1.-1.-1.-1.73569.5"
  UnivPos     (+00000000000000000000448BC5D99FEA +000000000000000000001DB806943F5E +000000000000000000001D2D6690F9CC)
  Orientation ( 0.616111746712322  0.711720561549839 -0.315146210320746  0.120594460696772)
  Velocity    ( 5.052320883929286e+000  1.022119359760036e+001 -2.767166358939599e+001)
  AngVelocity (-1.805275244923325e-004 -4.907250661918896e-005  1.574039013023385e-005)
  HUDMode      2
  PhysMode     1
  Orbit
  {
   Epoch           2456992.405787037
   Period          0.000176567724395136
   SemiMajorAxis   4.5388219904102e-005
   Eccentricity    0.0007436
   Inclination     51.6469
   MeanAnomaly     279.7014
   AscendingNode   355.0173
   ArgOfPericen    80.4977
   RefPlane        "Equator"
  }
}

But when I compare the position of the ISS in SpaceEngine with the position on http://spaceflight.nasa.gov/realdata/tracking, its not the same.

What I've done wrong?

Disasterpiece

Date: Monday, 01.12.2014, 00:40 | Message # 2

World Builder

Group: Users

United States

Messages: 640

Status: Offline

I forget the exact terminology, but SE uses a slightly inaccurate method of modeling orbits. This becomes apparent in events that occur over a short period of time (eclipses, exact position of the ISS) because of the compounded inaccuracy. I think that Space Engineer plans on fixing this in a later version of SE (not 0.9.7.2).

Also, I think this should be in bugs and troubleshooting.

I play teh spase engien

HarbingerDawn

Date: Monday, 01.12.2014, 05:10 | Message # 3

Cosmic Curator

Group: Administrators

United States

Messages: 8717

Status: Offline

Disasterpiece, no, that's not the cause. If you updated the Moons orbital elements on a regular basis with its current elements, then it would show an eclipse accurately if one was occurring on or around that date.

I think the issue might be that SpaceEngine doesn't correctly utilize Epoch data for spacecraft orbits. You can test with different Epoch values to see whether the orbit changes or not. If it doesn't, then that's the culprit.

All forum users, please read this!
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Orcinus

Date: Monday, 01.12.2014, 22:23 | Message # 4

Observer

Group: Newbies

Germany

Messages: 9

Status: Offline

Thanks for the answer,
when I change the Epoch value, the position of the ISS changes. So maybe the processing of the Epoch data is wrong. Could it be that there is an issue with the MeanAnomaly?

Destructor1701

Date: Tuesday, 02.12.2014, 15:09 | Message # 5

Pioneer

Group: Users

Ireland

Messages: 533

Status: Offline

I encountered a similar problem with the orbital elements of Siding Spring.

The stock elements were very close to accurate, but I wanted to achieve the accurate close pass to Mars of 125,000km, where the close pass in SE's stock elements was 500,000km. I understand that at the time of 0.9.7.1's release, the trajectory of the comet was not fully understood, so I'm not objecting to that minimal inaccuracy - I just wanted to use more up-to-date elements.

So, anyway, I repeatedly popped in elements from various sources, but each time, the comet was multiple AU away at the time and date of the close pass!

I must have entered the data wrongly, right?

Code

Comet "Siding Spring/C2013 A1 (Siding Spring)"
{
  ParentBody  "Sol"
  CometType  "C"
  AbsMagn     7.9
  SlopeParam  8
  Radius      2

  Orbit
  {
   Epoch            2456955.839684192762
   PericenterDist   1.398647410389588
   Eccentricity     1.000688626405008
   Inclination      129.0273584753412
   AscendingNode    300.9763462911545
   ArgOfPericenter  2.442757978652319
   MeanAnomaly    -0.003449276073378881
  }
}

Unfortunately, I cannot remember which site I got these data from, but it was probably one of these:

http://in-the-sky.org/cometephem.php?obj=ck13a010

http://theskylive.com/c2013a1-info

http://www.minorplanetcenter.net/mpec/K13/K13A14.html

None match the elements I have pasted into the Comets.sc file (one doesn't seem to have any elements available), so perhaps they've been updated or something.

n0b0dy

Date: Tuesday, 21.04.2015, 15:57 | Message # 6

Explorer

Group: Users

Pirate

Messages: 297

Status: Offline

Has anyone figured a way to import Real-time ISS (or any other) orbit elements into SE?

I understand it is probably impossible for SE to accurately calculate the true position of objects at its current development state but I wonder if it is possible to periodically ''feed'' it with updated data so that the position is roughly accurate for + or - a few days or at least hours from the time reference insertion point unsure

Sorry for asking this again in an old thread - I am trying to demonstrate SE to some friends and it would be cool if I could at least show them the beauty of it combined with some relative orbital accuracy smile

Jadestar

Date: Wednesday, 03.06.2015, 17:51 | Message # 7

Astronaut

Group: Users

United States

Messages: 70

Status: Offline

Quote n0b0dy (

)

Has anyone figured a way to import Real-time ISS (or any other) orbit elements into SE?

I do it by hand using the TLE's (two line elements) for the object.

It would be very cool if someone could write a script would query the NORAD TLE database - http://www.celestrak.com/NORAD/elements and the NASA/JPL's Horizon's database for solar system objects - http://ssd.jpl.nasa.gov/horizons.cgi and probes and would write a "spacecrafts.cfg" file which our SpaceEngine could use with any object you specified in the query or perhaps even a group of objects in a query.

It seems like a simple enough task for someone well versed in web query and data reformating.

Anyone?

Quote

I understand it is probably impossible for SE to accurately calculate the true position of objects at its current development state but I wonder if it is possible to periodically ''feed'' it with updated data so that the position is roughly accurate for + or - a few days or at least hours from the time reference insertion point

Indeed it would be.

Quote

I use Space Engine as a space visualization tool for kids which interests them in the space program and astronomy. I'd love such a capability as well.

There is a spreadsheet to crudely do this with Celestia's .ssc format.

http://www.lepp.cornell.edu/~seb.....html#2

Perhaps it can be modified?

I'd try to write something myself but I wouldn't really know where to begin and I am still trying (as someone with no 3D modelling skill) convert the James Webb Space Telescope to be accurately represented in Space Engine.

With Celestia's mainstream development pretty much dead* I'd hope to use Space Engine in a similar way but it will eventually require static orbits and more in the way of scripting (ie: Lua or something similar).

*I know about Celestia.sci but that project is moving at a snails pace and is not really mainstream.

I love Space Engine! I also love sci-fi and I love gaming but I'd love to do more to add real spacecraft and their accurate orbits to Space Engine.

Edited by Jadestar - Wednesday, 03.06.2015, 18:01

SanMarco

Date: Sunday, 30.10.2016, 17:01 | Message # 8

Observer

Group: Newbies

Ghana

Messages: 2

Status: Offline

Sorry I am new to the forum so I have to find an existing thread on which to tack a reply.

I would like to have Earth satellites and other man-made objects to visit in orbit etc. I am not sure how to add the ISS for example although there is an addon for it. Can it be found in correct static orbit once installed?

I know that Celestia does this and looking at previous discussion about ISS (1 to 2 years ago) it seemed it was planned for SE to have this functionality.

I think this would be the icing on the cake of an already very impressive product!

Mosfet

Date: Wednesday, 30.11.2016, 10:39 | Message # 9

World Builder

Group: Users

Italy

Messages: 754

Status: Offline

Hi SanMarco,
Right now it's not possible to assign a static orbit to objects when built in-game. It's still planned, I guess.
HarbingerDawn came up with a solution in his HST porting, which is suitable for ISS and others.
It consist to manually copy-paste orbital data previously saved into spacecraft.cfg file, you can find it in Space Engine /config folder.
So when you run SpaceEngine the object is in orbit.

"Time is illusion. Lunchtime doubly so."
Douglas N. Adams
My mods
Asus x555ub: cpu i5-6200u - ram 4gb - gpu nvidia geforce 940m 2gb vram

Edited by Mosfet - Wednesday, 30.11.2016, 10:40

Forum » SpaceEngine » Mods and Addons » Incorrect position of ISS

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