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Re: AO-40 Update 2003-04-17



JON
I completely agree with your comments on 3-axis stabilization.
To use a popular cliche
"The rewards are NOT worth the risks"
Also, as I understand it~~~~
If something goes wrong "there is no recovery"
Rick

----- Original Message -----
From: "Jon Ogden" <na9d-2@speakeasy.net>
To: "John Morley" <amsat@endeavour-usa.com>; <amsat-bb@AMSAT.Org>
Sent: Friday, April 18, 2003 10:50 AM
Subject: Re: [amsat-bb] AO-40 Update 2003-04-17


on 4/17/03 8:36 PM, John Morley at amsat@endeavour-usa.com wrote:

> Your report begs the question of "What happened to the plans to transition
> AO-40 to 3 axis stabilization"? The last report (that I remember) occurred
> sometime at the end of last summer, and included a detailed plan (posted
in
> German @ amsat-dl.org) to incrementally attempt 3 axis stabilization (so
as
> to recover if things went south) beginning in Nov. 2002 when conditions
> were favorable. Since that time, I haven't heard any further information.
A
> quick scan of the amsat-dl archives reveals no further discussion of this
> topic. Have I simply missed the follow-up, or is there no new news?

John,

Not to speak for Stacey, but from what I've read on this (and yes, I have
asked this question), the pucker factor for 3 axis stabilization is pretty
high.  It's a lot of risk and doesn't buy all that much for the cost of that
risk.  The software algorithm for the orbit of AO-40 is apparently much
different than the algorithm originally planned.  In addition, it is unknown
what the effects of the "mystery" effect would be on the 3 axis
stabilization.  Is there enough torque in the wheels to counteract it?
That's an unknown.  Plus with the damage to the craft from the "event" we
still don't know if this system is 100% working and will stay 100% working.
The wheels have been tested, but beyond that, I don't know if it's known if
there's damage.  We've had other systems work for a while and then fail (ie:
S1 TX).

I think the control crew are erring on the side of being conservative.
Perhaps when Project Eagle and P3E are both in orbit and working, we can try
such a thing.  Then if we lose the bird for some reason, we still have other
ones in operation.  But if we lose AO-40 now, we have no other HEO bird out
there that works.

As I understand it, in order to use the momentum wheels, the solar panels
must be deployed.  Once deployed, we can't spin stabilize the spacecraft
like it is now.  So if we deploy the panels, start stabilization and it
fails, we are hosed.  I think Stacey once said they think they could spin it
at a much slower rate if that happened, but will that even work?

We'll get no extra benefit or transceivers (OK maybe the HF receivers!) with
the panels open and 3 axis working due to the damage done.  So from that
standpoint, we just don't gain a lot.

Someone pointed me to a great writeup on AMSAT_DL when I asked this question
a couple months ago.  I'd suggest looking at some of the old updates there
which talks a lot about this.

73,

Jon
NA9D

-------------------------------------
Jon Ogden
NA9D (ex: KE9NA)

Citizen of the People's Democratic Republik of Illinois

Life Member: ARRL, NRA
Member:  AMSAT, DXCC

http://www.qsl.net/na9d   <- Updated on 1/22/03!!!

"A life lived in fear is a life half lived."


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