Geostationary objects are moving

Lots of geostationary satellites have some small wobble in their orbit, although this is usually only a fraction of a degree. You might have out-of-date orbital elements for this object. You can check like this:

Please open the satellite config dialog (alt-Z), and click "update now", and check there is no error message. After this, please check if you still have the problem. If you so, I would like you to attach this file:

  C:\Users\Detlev\AppData\Roaming\Stellarium\modules\Satellites\satellites.json

I can cross check it against mine and see if I can re-create the problem with it.

M

Hi Matthew,

thanks a lot for the quick answer.
I've updated the satellites and the problem remains. The file is attached.

Looking to your help files and and to the whitepapers I understand, that
the regulary update of the TLE - data corrects the one time positions.
When I briefly read the descriptions of the mathematical theory behind
the comuptation (e.g.
http://www.celestrak.com/publications/AIAA/2006-6753/AIAA-2006-6753.pdf)
and the limits in Appendix B, the programm does it's best but the
accuracy can't be better....

------
1. The maximum accuracy for a TLE is limited by the number of decimal
places in each field (Vallado,
2004:116). In general, TLE data is accurate to about a kilometer or so
at epoch and*it quickly degrades* (Hartman,
1993). We note that the SGP4 theory is capable of much better accuracy
through additional modeling and sufficient
observational data. Cefola and McClain (1987) noted that certain
low-inclination geosynchronous orbits exhibited
*large discrepancies from numerical simulations due to
oversimplifications in the node rate calculations*. Cefola and
Fonte (1996) showed that the addition of additional terms to the theory
could improve the overall accuracy by
almost an order of magnitude. Cappellucci (2005) showed that using
numerically generated state vectors and
performing an SGP4 orbit determination on the resulting ephemerides
produced errors representative of a numerical
technique. This is not unexpected as additional (continuous)
observations provide the needed observability over a
simple “3-obs per pass” approach (Vallado and Alfano, 1999). However,
the results diverge very rapidly once
outside the fit span of the orbit determination. We do not address orbit
determination here.
---------

It would be very nice, if you could verify, that the code works as
designed :-)

Best wishes from Burscheid, Germany.
Detlev

Am 09.03.2012 20:57, schrieb Matthew Gates:
> Lots of geostationary satellites have some small wobble in their orbit,
> although this is usually only a fraction of a degree. You might have
> out-of-date orbital elements for this object. You can check like this:
>
> Please open the satellite config dialog (alt-Z), and click "update now",
> and check there is no error message. After this, please check if you
> still have the problem. If you so, I would like you to attach this file:
>
> C:\Users\Detlev\AppData\Roaming\Stellarium\modules\Satellites\satellites.json
>
> I can cross check it against mine and see if I can re-create the problem
> with it.
>
> M
>

Same issue here (Stellarium 0.11.4 on Mac). Geostationary items move (a lot, ex, Intelsat 707 in which I am interested is seen, according to Stellarium, at Az/Alt 322/35 from Bariloche, Argentina, and in exactly one year will be in 279/1...) and are therefore almost never in the correct place.
Too bad as I wanted to check the signal of the sun in a microwave dish and it would have been easy to see when the sun goes at the vertical of the satellite...

BTW, don't know if it clear, but not only the position in a distant past/future is wrong. The current position of the satellite is also wrong.
If I go to New York, USA, and look at Intelsat 707 (just updated the files using reload from the configuration file), it is SW, while it should be SE (New York is 73W, Intelsat 707 53W). dishpointer.com gives the the expected direction, but not stellarium.
The relevant part of the last satellite.json file I have is:

                "23816":
                {
                        "comms": [],
                        "groups": ["geostationary"],
                        "name": "INTELSAT 707 (IS-707)",
                        "orbitVisible": false,
                        "tle1": "1 23816U 96015A 11345.31390747 -.00000269 00000-0 10000-3 0 3108",
                        "tle2": "2 23816 0.0142 351.8754 0003576 269.3710 238.4581 1.00270608 57671",
                        "visible": false
                },

dishpointer.com tells me:
Elevation: 38.2°
Azimuth (true): 149.5°
stellarium:
Az/Alt:+214.../+36...

Now everything is OK

laik, what you meant?

Sorry for that, but i was wrong. There was an update in TLE, and geostationary sattellites moves on good positions, but still are moving when date is change.
Why i can't edit or delete my posts in this thread?

You can hide your message.

Hi Alexander, hi Laik,

I've tested it with the current version 0.12.4 and the problem still exists.
But thanks for all your efforts and thoughts.

Best wishes
Detlev

Am 09.02.2014 15:52, schrieb Alexander Wolf:
> You can hide your message.
>

Well, this task may be not resolved in general case, because geostationary satellites are active and TLE has valid range for 72 hours.

The bug report was moved to https://github.com/Stellarium/stellarium/issues/405