Re: [Q] Re: NOSS reentry tracks

Björn Gimle (
Fri, 12 Mar 1999 08:00:30 +0100

Though this should be too late for this decay, it can be of interest for
the future:

>While the sat. is in Earth's shadow, what sort of magnitude might we
>expect? Object will be moving far too quickly for a telescope... I have
>70mm aper. binocs and hope that will be enough. Will it?
>If not, is the purpose of the observation to actually witness the reentry
>(1000-1 at best)?
Since the Sun is probably below -20 degrees at your location, the rocket
illumination from crescent Earth and the atmosphere is probably neglible.

The Moon is at least 14 magnitudes fainter than the Sun, and although this
gives you a chance to see Iridium moon glints, you would need the 
Mt.Palomar to see a rocket ;-)>

So, the intention is not to miss this once-in-your-life chance, if it
actually fell in your area.

>If the sat is not on-time, should I expect it to be early or late?

Since you only see it if it is actually in the final decay stage,
the average period is lower than predicted if the elset pre-dates the pass.
Thus, it will be early, depending on the age and predicted lifetime from
the elset.

If you are predicting from a LATER SatEvo elset, the decaying satellite
will instead be late, for the same reason.

>Finally, I assume tumbling... any clues as to the flash rate?
I have no first-hand experience of decays, and reports I have seen
describe only the break-up into swarms of parts, and intensity changes -
no tumbling probably.

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