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Re: Re: [ans] AMSAT Special Bulletin



>I had the exact same thoughts.  However, an explosion occurring without
>throwing at least one piece of shrapnel out into space would be highly
>unlikely.

My followup message was meant to show that NORAD wouldn't necessarily
see any such small objects, especially if they were ejected into
different orbits that took them outside the radar antenna beamwidth at
the time of the radar tracking pass.

>  Additionally, I think that if something had exploded, it would
>have somewhat changed the shape of the craft.  For example, if an explosion
>occurred, then one of the solar panels might have popped out.  Or you'd have
>a mass of metal sticking out from somewhere.  Any of that would most
>definitely change the radar cross section of the bird.

The radar cross section of any object (except for a uniform sphere)
changes with the viewing angle. Depending on the orientation, there
might be "glints" from flat surfaces that would greatly increase the
cross section at certain angles (think of Iridium flares).  At other
orientations the cross section might be much lower.  My point is that
these normal variations might be quite a bit larger than any change
caused by a small explosion.

It would be nice to know the observed radar cross section as a
function of time. Back in 1983 they routinely took fast fourier
transforms (FFTs) of the return signal to estimate the spin rate of
the spacecraft. Even a small explosion might have created enough
moment to change the spin rate from what it was known to be prior to
the loss of telemetry.

Phil



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