Re: [amsat-bb] AO-40 Update, 2004-01-28

[w1gud@xxxxxxxxxxxxxxx]

Stacey...I just wanted to thank you for all you and the rest of the team are doing for the AMSAT community. Please be aware of how much we appreciate what you folks world-wide are doing.

73, Warren W1GUD
Tampa Fla
Amsat Member

----- Original Message -----
From: "Stacey E. Mills" <w4sm@AMSAT.Org>
Date: Wednesday, January 28, 2004 3:05 pm
Subject: [amsat-bb] AO-40 Update, 2004-01-28

> 
> At the moment we have nothing really new to report regarding AO-
> 40, other 
> than that we are trying to see if observers in Europe can hear the 
> K-Tx on 
> today's orbit.  This is a bit of a long shot given the less than 
> perfect 
> squint angles and some really horrible snow/ice at the receiver 
> stations, 
> but we are trying.  If we have 10 - 14 volts available, the IHU-1, 
> MUX 
> hardware control unit, and receivers may be functional, but the S2 
> Tx may 
> not wish to start up in "cold" mode from that voltage.  It was 
> never 
> designed to run below 20 volts.  We are seeing if the K-Tx will 
> respond at 
> these voltages.  As mentioned before, we are sending simple 
> machine code 
> commands to try to activate this hardware and switch to the 
> auxiliary 
> battery.  If we have close to 10 volts available, these commands 
> should 
> work.  As a safety measure, each command session ends with 
> commands to shut 
> off all of the transmitters, since we would not want to leave them 
> on line 
> at these low voltages.
> 
> If the main battery has us clamped at a voltage where the above 
> will not 
> work, we will have to wait to see if solar angle improvements 
> help, or if 
> one of the bad cells eventually goes "open".
> 
> Although we have not had time to read the bulletin board much, and 
> we can't 
> claim to fully understand what has happened, it is clear that 
> operator 
> practices, though not always perfect, had absolutely nothing to do 
> with 
> this event.  The fact that the passbands cut off on Sunday was an 
> example 
> of the kinds of safety features that we have in place to protect 
> the 
> electronics on board.  There are also input AGC's and output 
> limiters.  AO-40 was designed to withstand all that you can throw 
> at 
> it.  Although there was a lot of passband activity on Sunday, and 
> under 
> really marginal conditions heavy usage could put us in transiently 
> a 
> negative power budget, it is now clear that it was the failing of 
> another 
> cell on the main battery that caused the passband shutdown at that 
> time.
> The main batteries consist of 20 40 amp-hour cells arranged on 
> three of the 
> radial support arms inside the spacecraft. There are two packs of 
> 7 cells 
> and one pack of 6 cells.  It is entirely possible or even probable 
> that the 
> main batteries suffered some damage during the 400N motor event.  
> One clue 
> to this is the fact that we lost two of the three temperature 
> sensors 
> attached to these packs, and since that time we have been able to 
> measure 
> the temperature of only one of the three packs.  It may well be 
> that this 
> was the only "normal" main battery pack.
> 
> One mystery in the telemetry is where the "energy" is going from 
> this 
> battery failure.  With the exception of the "heat pipe" spike, 
> which we 
> believe is not real as discussed before, there are really no 
> changes in 
> temperatures anywhere over the next 15 minutes.  The answer MAY be 
> that the 
> bad cells in fact had deteriorated to the point that they had very 
> little 
> storage capacity left and so had little energy to dissipate.  The 
> aux. bat. 
> was probably only a few percent charged at the pre-event voltage 
> and had 
> little energy to contribute to the event.  The temperature on 
> either of its 
> two packs does not change during this time, supporting this 
> conclusion.
> The above (except the operator practices part), is our best 
> understanding 
> of things at the moment and is always subject to change.  We'll 
> keep you 
> posted.
> 
> --W4SM for the AO-40 Command Team
> 
> 
> PERSONAL NOTE:
> Like my colleagues on the command team, I have lived and breathed 
> AO-40 for 
> over four years.  All of us can almost mentally decode 400 bps 
> PSK.  We 
> hear it in our sleep. I was watching the battery voltage telemetry 
> at the 
> exact moment that the voltage dropped precipitously.  In my "day 
> job" I 
> have frequently watched catastrophic events unfold in human 
> beings, and the 
> feeling was EXACTLY the same.  Part of my day job is to have to 
> make quick 
> decisions during times such times, decisions that can have serious 
> consequences.  I was instantly aware that we had a serious power 
> event, and 
> I considered cutting the main battery loose and trying to run on 
> the nearly 
> completely discharged and untested under load aux. battery.  
> However, 
> because I did not have a clear understanding of where the primary 
> fault 
> was, I elected to watch things and try to figure out what was 
> happening.  The general rule of, "when in doubt wait to 
> understand" works 
> most of the time...  In this case it didn't, and I'd sure like to 
> live 
> those minutes over again and cut the main battery loose.  
> Hindsight is 
> always 20-20.  Of course, if it had crashed anyway, then I'd 
> really be 
> beating myself up.
> 
> If it's at all possible to bring AO-40 back, we will.  If the 
> voltage is 
> clamped low and there is no other damage, we may end up waiting a 
> long time 
> for a cell to "open", hopefully not as long as for AO-07.  ..or it 
> may 
> happen today.  No success for even weeks or months does not mean 
> that we 
> won't eventually be successful.  We will sure keep trying.
> 
> Several of you have written very nice notes of support.
> Thank you.
> 
> 
> 
> -- 
>  
> ________________________________________________________________________  Stacey E. Mills, W4SM    WWW:  http://www.keplerian.com
>    Charlottesville, VA     PGP key: http://www.keplerian.com/key
>  
> ________________________________________________________________________  
> 
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