[Kstars-devel] Re : Satellites in KStars

[Bernard GODARD]

Hi Akarsh,

The SGP4 C library used by KStars to handle TLEs was developed by
Jean-Baptiste BUTET , Patrick Chevalley and Vincent Suck based on
NORAD Spacecraft Report #3 (a very old document that you can find on
the web).
The SGP4 routine returns position, velocity of thew spacecraft in the
TEME (True Equator Mean Equinox) frame of epoch (if I remember
correctly). The library also converts to azimuth/elevation in the
topocentric frame of the observer. I think the library has been
successfully checked standalone against other libraries and against
data from Heavens Above.

However, there were problems in Kstars. Among them :
- longitude sign convention in the interface of the routines
- graphical problems :  ticks on the orbit pass being drawn ... far
from the orbit path

You should read all the previous e-mail in the archive containing the
words satellites, SGP, SGP4, TLE, NORAD, heavens above...

In the long term, the C library has to be replaced by the new SGP4
algorithm that you can find here :
http://www.centerforspace.com/downloads/files/pubs/AIAA-2006-6753.pdf
I wanted to do this but I really don't have time at the moment.

You can also find the C++ code for the new algorithm on Vallado's website :
http://celestrak.com/software/vallado-sw.asp

If you need more info about TLEs, have a look at Kelso's website :
http://celestrak.com/

I 'm afraid I can't help more at the moment because I'm lacking the time.

Good luck and clear skies,

         Bernard






> Date: Sat, 7 Mar 2009 23:54:24 +0530
> From: Akarsh Simha <akarshsimha at gmail.com>
> Subject: [Kstars-devel] Satellites in KStars
> To: KStars Development Mailing List <kstars-devel at kde.org>
> Message-ID: <20090307182424.GK16012 at PENGUIN>
> Content-Type: text/plain; charset=us-ascii
>
> Hi
>
> I'd really want to re-enable satellites in KStars, before KDE 4.3
> release.
>
> Unfortunately, I'm new on the block, and don't know what was the
> problem with satellites that led to their removal. At some point, I
> think I recall that HST would cross the sky in KStars every 5 minutes!
> But that apart, I don't know anything about the longitude problem that
> was being discussed on the list.
>
> It would be nice if someone could help me by telling me what I need to
> fix and how I need to go about doing it. I could cross check KStars
> against satellite data from http://www.heavens-above.com (which is
> what we amateurs use for satellite predictions)
>
> Thanks
>
> Regards
> Akarsh
>
>