re: Saw Mir & STS-86

Philip Chien (
Sat, 27 Sep 1997 18:27:27 -0400 said:

>I saw Mir & STS around 12:25-12:30 UTC 27-Sept-97 both in the
>sky at the same time perhaps 60 degrees apart about 7.5 hrs.
>before docking.  STS-86 was first followed by Mir.

not unless you were looking at it from a *rather* unusual angle ...

When travelling to Mir the shuttle is in a _lower_ orbit.  (for obvious
reasons).  So the shuttle has to 'catch up' with Mir.  The shuttle launches
when the orbital plane matches Mir's orbital plane (i'm simplifying a bit.
It's slightly different because it takes time for the shuttle to reach
orbit and the window can be expanded with performance as a tradeoff, etc.).
So Mir can be anywhere in its orbit relative to the shuttle at launch.  But
since the shuttle's in a lower orbit it will quickly catch up with Mir by
travelling a bit 'faster' around the world on each orbit.  So the shuttle
is always 'chasing' Mir until the docking occurs.

If, for some reason, your tracking program shows the shuttle ahead of Mir,
then either you haven't updated your elements since the most recent shuttle
burn to raise its orbit up to Mir's altitude or ...

They overshot their target!

Philip Chien [M1959.05.31/31.145//]