Re: Warning for odd TLE

From: C. Bassa via Seesat-l <seesat-l_at_satobs.org>
Date: Mon, 30 Mar 2020 21:43:57 +0200
In Leo's case it is the Dundee SGP4/SDP4 code which will only
propagate objects with mean motions between 0.035 and 18 revs/day. See
https://gitlab.com/pscrawford/dundee_sgp4/-/blob/master/sgdp4.c#L226

It turns out that in this particular sattools program I had forgotten
to catch the error that the Dundee code throws.

Regards,
    Cees

On Mon, Mar 30, 2020 at 9:35 PM Michael R Thompson via Seesat-l
<seesat-l_at_satobs.org> wrote:
>
> Leo,
>
> What kind of error messages are you getting?
>
> For what it's worth, I believe that that object may be hitting a limit of the propagator algorithm itself.  One of my implementations of SGP4 definitely fails, I'll see if I have anything for SDP4 coded up.  For something this high, it can definitely break some simplified general perturbations-based models.
>
> Thanks,
> Michael
> ________________________________
> From: Seesat-l <seesat-l-bounces+thomp376=purdue.edu_at_satobs.org> on behalf of Jonathan McDowell via Seesat-l <seesat-l_at_satobs.org>
> Sent: Monday, March 30, 2020 3:02 PM
> To: Leo Barhorst <leobarhorst_at_gmail.com>
> Cc: Seesat-L <seesat-l_at_satobs.org>
> Subject: Re: Warning for odd TLE
>
> I'll note that the mean motion (*not* mean anomaly) of 0.0347 is correct
> for this object. It was 0.04 but
> further lunisolar perturbations have  lowered the mean motion even further.
> So it's worth making clear that the issue is a limitation of the software,
> not an error in the TLEs.
>  - Jonathan
>
>
> On Mon, 30 Mar 2020 at 14:24, Leo Barhorst via Seesat-l <seesat-l_at_satobs.org>
> wrote:
>
> > Hello all,
> >
> > Last week I had problems reducing with Sattools the images I took.
> > The cause of the problem was the TLE for NORAD 39459 that has a Mean
> > Anomaly of 0.03 rev/day.
> >
> > After removing this TLE the program worked normally.
> >
> > This evening I saw in the recent downloaded catalog.tle that this TLE was
> > still present with MA = 0.03
> >
> > So if you have problems this may be the cause.
> >
> > Greetings
> > Leo Barhorst
> > _______________________________________________
> > Seesat-l mailing list
> > http://mailman.satobs.org/mailman/listinfo/seesat-l
> >
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Received on Mon Mar 30 2020 - 14:44:42 UTC

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