[FPSPACE] Parameters of the Iridium/Kosmos collision wanted

[Geert Sassen]

There is a very nice toolkit for assessing orbital collision risks at:

http://celestrak.com/SOCRATES/

Looking through the lists I was quite amazed at how often 'close encounters'
between satellites occur and how close some of them regularly come, I always
rated the risk of a collision as far smaller then it appears from the
calculations.

And according to the story, the Iridium collision did not even make it in
the top-10 of highest risks prior to the event! At those speeds and with
almost 90 degrees intersection you need only a very, very, minor error in
the calculations and a 'low risk' encounter turns into a collision...

Knowing that apparently orbital measurements can still show large enough
errors that an encounter is 'missed' as a high risk event is not a very
assuring thought, bearing in mind that the ISS and especially Hubble are
still down below that debris cloud..

Regards,

Geert

On Sat, Feb 21, 2009 at 5:51 PM, John Locker <john at satcom.freeserve.co.uk>wrote:

> Hi Erik
>
> Unfortunately as the list was down much of last week a lot of   data  on
> the
> collision just didnt appear here.
>
> As soon as the info was released I created this animation with up to date
> elements
>
> http://i39.tinypic.com/2vbk75z.gif
>
> You can see it was pretty much a side on impact.
>
> To get the relevant numbers  you need to sign up to Space-Track and draw
> down historic data going back to before the 10th....then re run the
> tracking....
>
> John
>
>
>
>
> ----- Original Message -----
> From: "Erik Tronstad" <erik.tronstad at nilf.no>
> To: <fpspace at friends-partners.org>
> Sent: Saturday, February 21, 2009 10:44 AM
> Subject: [FPSPACE] Parameters of the Iridium/Kosmos collision wanted
>
>
> >
> > Can anyone provide pre-collision orbital parameters for Iridium 33
> > and Kosmos 2251? Perigeum, apogeum, inclination and orbital period
> > are the parameters I would like to know.
> >
> > Aviation Week & Space Technology has a diagram on pages 20-21 in the
> > Feb. 16, 2009 issue indicating a 90 degrees collision angle. Is this
> > approximately correct? AW&ST also reports a relative velocity of 7
> > mi/s (ca. 11,2 km/s) immediately prior to the collision. This abides
> > well with a 90 degrees collision angle, supposing both objects had an
> > orbital velocity around 8 km/s.
> >
> > Can anyone provide the launch date for the Iridium 33 satellite?
> >
> > Erik Tronstad
> >
> > _______________________________________________
> > FPSPACE mailing list
> > FPSPACE at friends-partners.org
> > http://www.friends-partners.org/mailman/listinfo/fpspace
> >
>
>
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-- 
Geert Sassen
weblog: http://geertsassen.web-log.nl
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