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Old October 19th 11, 10:42 PM posted to sci.astro.satellites.visual-observe
DougD
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Posts: 19
Default Same satelite twice???

In article , Patty Winter wrote:

Anyways I was sitting in my hot tub tonight staring
up at the stars when I noticed a fairly fast paced bright object moving
south it went really bright and then dimmed out and I could no longer
follow it. About 15 minutes later the same object appeared in the exact
same spot only dimmer than the first time and steadily got dimmer till
it vanished. Can someone explain what is happening?


That wasn't the same object; it was two objects in the same orbit. A
satellite in low earth orbit typically takes about 90 minutes to come
around again.

If you saw each one for only 5-10 seconds, they may have been Iridium
satellites. Otherwise, it was probably two parts of a single spacecraft,
and I don't recall which spacecraft have that situation. Perhaps someone
else here will know.


Patty


To add to this, it could have also been a pair of satellites from a group,
such as the NOSS, which can be spotted one, two or three in a group,
or sometimes one after the other. OR, as Patty pointed out, it could be
parts of one object that has broken into two, or say a satellite and
the rocket booster that put it in orbit. The change in brightness could
be from all sorts of reasons, the first that comes to mind is even though
it was only 15 minutes of difference, your location relative to the Sun,
which is what is illuminating the object that you are seeing have changed
over that amount of time. So, as the Sun moves away or approaches you,
the brightness will change relative to the sat's position between you and
the Sun and the distance and angles that is it's path. Not the most
elegant explanation, but I think you'll get it..

d.