RE: OTV-5 manoeuvered?

From: Ted Molczan via Seesat-l <seesat-l_at_satobs.org>
Date: Fri, 20 Apr 2018 10:35:35 -0400
Mike wrote:

> Tristan Cools posted:
> 
> >I think I saw it almost 8 minutes early at Bruges, Belgium yesterday April
> >19 2018.   Time of observation: 20h UTC.  I took a picture of it but I'm
> >almost sure it is OTV 5 !
> 
> Assuming that the maneuver had taken place 24 hours earlier, I created
> a pseudo-observation for 8 minutes early to generate the following guess:
> 
> OTV 5 guess
> 1 42932U 17052A   18109.82112174 0.00000000  00000-0  00000-0 0    03
> 2 42932  54.4928 103.5230 0008000 204.5387 155.4612 15.79951988    01
> 
> Of course if the maneuver took place even less than 24 hours earlier,
> then the new mean motion would be even larger and it would be early
> even compared to this guess.

Repeating ground tracks have been a feature of all OTV missions to-date. Until its apparent manoeuvre, OTV 5's ground
track nearly repeated after 31 revs in 2 days. All four previous OTV missions spent at least some time in such an orbit,
and it represented a large fraction of the orbital life of OTV 2 through OTV 4.

All except OTV 4 spent at least some time in an orbit that repeated after 47 revs in 3 days. At OTV 5's inclination, the
required mean motion is about 15.92 rev/d. Assuming Tristan saw it 8 minutes early, then there is a good chance it is in
a 15.92 rev/d orbit. None of the other historical repeating ground tracks would have a higher mean motion. As Mike said,
that would place the manoeuvre less than 24 hours earlier. I imagine that it occurred within range of one of the AFSCN
ground stations.

Tristan, can positions be reduced from your photo?

Ted Molczan


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Received on Fri Apr 20 2018 - 09:36:53 UTC

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