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Re: Re: The hard questions..



I have to agree.  There's an enormous amount of data analysis and 
strategy involved in keeping a sat alive, and few that haven't done it 
themselves appreciate how careful you have to be to get it right.  
Eventually some contingency you couldn't possibly have anticipated will 
get you, especially when the only way to catch it would be to take some 
preventive action you would have had no way to know was needed when it 
was time to take that action.  I don't consider this grounds for 
putting anyone's privies in a wringer, especially working around the 
unknowns of the propellant event shortly after launch which, folks here 
may remember, was the last time we thought we'd never hear from AO-40 
again.

It's possible leaving the transmitters offline for an orbit or two 
might reduce the power demand enough to let the main battery fail open 
faster and bring up the aux battery and thus the IHU, transmitters, 
receivers, beacon, and everything else.  But like any other change in 
the program, that will have to be carefully evaluated to catch possible 
catastrophic side effects.  If the current commanding allows the 
control stations to verify that the sat is actually receiving the 
commands and the energy expended in the transmission is negligible in 
terms of the power budget, then I'd say it's not worth changing ..

On Sunday, Feb 15, 2004, at 23:22 US/Central, Stacey E. Mills wrote:

> Charging the aux. battery would have accomplished nothing unless the 
> shorted main battery were also taken off-line.  Conversely, connecting 
> the discharged aux. battery to the mains at the extreme low voltage 
> trigger caused no problem, since the voltage level was well below 
> normal charge voltage and virtually no current flowed into the aux. 
> bat. during the switch-in. The only course of action that would have 
> been helpful, would have been to take the main battery off-line and 
> connect the aux. battery.  Even in its fully discharged state, the 
> aux. battery would have come up to a functional voltage virtually 
> instantly.  With the fantastic power of hindsight, we could have 
> altered the extreme low voltage code to switch the main battery 
> off-line, or as I've said before, I could have done this manually 
> during a 10 minute window when things fell apart and by pure luck I 
> happened to be watching the telemetry.  This may seem like an obvious 
> idea at the moment, but it was far from obvious at the time.  
> Switching between two separate batteries is never a decision to be 
> made lightly.  You may consider this an "oop-sie" that should put my 
> anatomy in a wringer,  but I do not.
>
           --... ...-- -.. . -. ..... ...- -...
                   Bruce Bostwick N5VB

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