Re: STS 81 and MIR Docking

Philip Chien (
Wed, 1 Jan 1997 08:30:07 -0500

Nick Budd <> said:

>I didn't fully explain but.........
>I shall be flying back to London from Orlando that evening and a large
>proportion of the flight will be "near" 51 degrees N. Hence I'm hoping to see
>them from the cockpit. Not as difficult as it sounds - I did see STS77 and Mir
>earlier this year.

>>Mir will pass over the KSC area shortly before the STS-81 launch (they may
>>even get to see it!).
>I didn't even think about that - but according to predictions it will still
>be in shadow.

Yes, certainly people on the ground won't be able to see Mir visibly, but
the Mir crew should be able to see the shuttle launch - lighting up the
Central Florida area.  And it wouldn't be the first time - or even the
first time for Mir crewmembers to see an Atlantis launch!

>>  Atlantis will launch directly in to the 51.6 degree
>>inclined orbit in Mir's orbital plane.  But it will be far behind Mir and
>>in a very elliptical orbit with a very low perigee.  Over a couple of days
>>Atlantis will 'catch up' with Mir and raise its orbit at the appropriate
>>point to match Mir's orbit.  Depending on when Atlantis launches within its
>>window, the exact burns would vary, and the actual rendezvous and docking
>>would occur on either the 3rd or 4th flight day.
>According to the state vectors someone sent me, the docking occurs at 1 day
>19 hrs Mission Elapsed Time.

That assumes a launch in the early part of the window.  As I noted above a
launch in the later part of the window would result in a docking about
aday later.

I haven't examined the STS-81 profile in enough detail to determine when
the NC burns would occur, but that is highly dependent on the exact launch
time and Mir's exact position in its orbit (which is highly dependent on
exactly when the upcoming orbital adjust burn takes place).

>I shall just be grateful if NASA don't postpone the launch for
>about the third mission running.

Now who made you believe that - some reporter who doesn't know what he's
talking about???

The majority of shuttle launches occur on the first try.  On the average it
takes about two tries for each launch -- and that's including the three
missions which had extraordinary delays.

Even though the Mir rendezvous missions have very short launch windows
they've all launched within two tries (one in the case of STS-79).

I suppose it's human nature to remember delays and forget the ones which
launch on the first try ...

Philip Chien, KC4YER
Earth News - space writer and consultant
note new E-mail address -