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RE: RE: AO-40 Update, 2004-02-03



I see.  Well it would be the same problem, if you don't
know where you are, it is hard to know where to go. We
could try to spin up the wheels and by doing so, we would
impart the equal but opposite angular momentum to the spacecraft.
Without knowing our attitude, this could make matters much worse
and completely outside of our "controllability region".

It was always the plan to use the magnetorquers to dump excess
angular momentum from the wheels when they began to come near
the "limit" of controllability as defined by the design and our
experience.

I am not privy to the day to day decisions of the controllers and
I am answering on the basis of the physics involved and my early
involvement in the AO-40 project and its design which I ended
years before it was integrated.  That being said, not much changed
in the attitude control system early design and we are using the
same kinds of sensors we used on earlier spacecraft so I suspect
I am too far off the mark.


73's
Bob
N4HY

-----Original Message-----
From: owner-AMSAT-BB@AMSAT.Org [mailto:owner-AMSAT-BB@AMSAT.Org]On
Behalf Of kgschaffrath@beckman.com
Sent: Tuesday, February 03, 2004 1:24 PM
To: amsat-bb@AMSAT.Org
Subject: [amsat-bb] RE: AO-40 Update, 2004-02-03


>We currently use magnetorquers and I doubt anyone would say okay to
>trying the wheels after such a long absence of control.
>
>Long before we got there, a combination of perturbations, mystery
>force, etc. would have imparted all sorts of angular momentum to
>the spacecraft and it would probably be in a tumble.  With our
>sampling rate for the attitude sensors, cameras, etc. we could with
>some help from radio measurements, get some idea about magnitudes of
>rotational velocities and infer some things but I think we would have
>to be extraordinarily lucky to infer the actual vectors and their
>magnitudes and I do not know if we could time the torquers to the
>degree necessary to overcome the unknown, but guessed at, rotations.
>If it begins to tumble and we cannot get good readings on our
>attitude, we would be basically out of luck.
>
>Bob
>N4HY"


First off,  If the attitude makes the satellite useless of course someone
will
ok
any extreme measures to make it useful. And yes of course it may be so out
of whack that the torquers cannot be useful or even used.

What the hell do you think i asked about using the wheels for?

DUH!

Now , back to the original question.
IF we had to, would there be enough power without the batteries?


Keith N6ORS




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