[amsat-bb:74614] AO-40 Update, 2004-01-26

["Stacey E. Mills" <w4sm@xxxxxxxxxxxxx>]

On orbit 1486, the main battery voltage ran lower than expected.  This was 
due in part to usage and high solar angle as mentioned previously, but even 
after the passbands were shut off automatically the voltages did not come 
back up as expected, in spite of apparently positive battery charge 
currents.  At the beginning of the eclipse on orbit 1486 at MA =225, the 
battery voltage rapidly dropped just below the S2 Tx cutoff voltage of 24.0 
volts and the S2 Tx shut down. to protect the battery and IHU's.  The 
eclipse ended at about MA=237, approx. 55 minutes later.  We expect the S2 
Tx to start back up as programmed at MA =2 (as I type this), though it has 
been known to be  "balky" before on restarts and could require manual cycling.

The command team is investigating this anomaly to determine if the main 
battery may have developed a single bad (shorted) cell or if there is a 
problem with the battery set voltage, solar array set voltages, or other 
problem.  Until we sort this out the passbands will be off for one or more 
orbits.  If the battery charge or array set points are wrong, they can be 
changed.  If we have one bad ( shorted ) cell we can reset charge/trigger 
points to account for this, and we have the completely redundant auxiliary 
battery, if needed.  We hope to be able to work through this and correct 
things without too much down time.

We'll update you here as soon as we know more.

--W4SM for the AO-40 Command Team



-- 
  _______________________________________________________________________
  Stacey E. Mills, W4SM    WWW:    http://www.keplerian.com
   Charlottesville, VA     PGP key: http://www.keplerian.com/key
  _______________________________________________________________________

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