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AO-40 Update, 2004-02-15


Attempts to switch AO-40's batteries and turn on the S2 (or K) transmitter 
continue on every orbit. So far they have not been successful.  The chart 
below shows the projected ALON changes resulting from the mystery effect 
through the end of April.  Note that this effect reduces ALON about 11.8 
degs/week, and does not affect ALAT.  The minor changes seen in ALAT are 
due to precession of the orbital elements, effectively changing the 
spacecraft's reference system for ALON/ALAT measurement.

Attempts are underway to have one or more very large radio telescopes 
(non-amateur) listen for the receiver local oscillators.  These are well 
shielded and this search may be negative even if the receivers are powered 
up properly.  Results and further details will be reported when they become 
available.

Tests of the auxiliary batteries at the Amsat lab in Orlando confirm the 
benign behavior of these cells when subjected to a scenario duplicating 
that experienced on AO-40.  Extra main battery cells are not available for 
testing.  Tests also show that the battery switching relay requires 12 
volts to switch reliably.  The receivers and IHU require 10 volts for 
operation.  The S2 transmitter was not designed to work below 20 volts.

Some minor changes have been incorporated into the simple machine code 
commands to switch batteries and
receivers in order to optimize their chances of success.

As we have mentioned before, we believe that we have a shorted main 
battery, and we may have to wait for a cell to open to regain voltage and 
control.  This may be a long-term prospect.  Short-term failure does not 
predict long-term results for this problem.  There is no reason to believe 
that the BCR's are damaged or will be damaged by the shorted battery 
pack.  The BCR's are designed to function with the solar panels extended, 
when they have to handle over 3 times the power available in spin mode.

The AO-40 Command Team would like to thank all of you for your support and 
good wishes.  When any additional information becomes available we will 
report it here as quickly as possible.

--W4SM for the AO-40 Command Team


****************************************************************


    AO-40  ATTITUDE - PRECESSION BEHAVIOR / W4SM
       Mystery Effect = -11.800 degs ALON/week

        DATE            ALON   ALAT    SA     ILL%
---------------------------------------------------
  2004  Jan  27 [Tue]  350.0   -3.0   37.8    79.0
  2004  Jan  29 [Thu]  346.3   -3.0   32.5    84.4
  2004  Jan  31 [Sat]  342.6   -2.9   27.1    89.0
  2004  Feb  02 [Mon]  338.9   -2.9   21.8    92.8
  2004  Feb  04 [Wed]  335.2   -2.9   16.5    95.9
  2004  Feb  06 [Fri]  331.5   -2.8   11.1    98.1
  2004  Feb  08 [Sun]  327.8   -2.8    5.8    99.5
  2004  Feb  10 [Tue]  324.1   -2.8    0.5   100.0
  2004  Feb  12 [Thu]  320.4   -2.7   -4.9    99.6
  2004  Feb  14 [Sat]  316.7   -2.7  -10.2    98.4
  2004  Feb  16 [Mon]  313.0   -2.6  -15.6    96.3
  2004  Feb  18 [Wed]  309.3   -2.6  -20.9    93.4
  2004  Feb  20 [Fri]  305.6   -2.5  -26.3    89.7
  2004  Feb  22 [Sun]  301.9   -2.5  -31.6    85.2
  2004  Feb  24 [Tue]  298.2   -2.4  -37.0    79.9
  2004  Feb  26 [Thu]  294.5   -2.3  -42.3    74.0
  2004  Feb  28 [Sat]  290.8   -2.3  -47.6    67.4
  2004  Mar  01 [Mon]  287.1   -2.2  -53.0    60.2
  2004  Mar  03 [Wed]  283.4   -2.2  -58.3    52.6
  2004  Mar  05 [Fri]  279.7   -2.1  -63.6    44.4
  2004  Mar  07 [Sun]  276.0   -2.0  -68.9    36.0
  2004  Mar  09 [Tue]  272.3   -2.0  -74.2    27.2
  2004  Mar  11 [Thu]  268.6   -1.9  -79.4    18.3
  2004  Mar  13 [Sat]  264.9   -1.9  -84.5     9.7
  2004  Mar  15 [Mon]  261.2   -1.8  -87.4     4.5
  2004  Mar  17 [Wed]  257.5   -1.7  -83.7    11.0
  2004  Mar  19 [Fri]  253.8   -1.7  -78.6    19.7
  2004  Mar  21 [Sun]  250.1   -1.6  -73.4    28.6
  2004  Mar  23 [Tue]  246.4   -1.6  -68.1    37.3
  2004  Mar  25 [Thu]  242.7   -1.5  -62.8    45.7
  2004  Mar  27 [Sat]  239.0   -1.5  -57.5    53.7
  2004  Mar  29 [Mon]  235.3   -1.4  -52.2    61.2
  2004  Mar  31 [Wed]  231.6   -1.3  -46.9    68.3
  2004  Apr  02 [Fri]  227.9   -1.3  -41.6    74.7
  2004  Apr  04 [Sun]  224.2   -1.2  -36.3    80.5
  2004  Apr  06 [Tue]  220.5   -1.2  -31.1    85.7
  2004  Apr  08 [Thu]  216.8   -1.2  -25.8    90.1
  2004  Apr  10 [Sat]  213.1   -1.1  -20.5    93.7
  2004  Apr  12 [Mon]  209.4   -1.1  -15.2    96.5
  2004  Apr  14 [Wed]  205.7   -1.0   -9.9    98.5
  2004  Apr  16 [Fri]  202.0   -1.0   -4.6    99.7
  2004  Apr  18 [Sun]  198.3   -1.0    0.6   100.0
  2004  Apr  20 [Tue]  194.6   -0.9    5.9    99.5
  2004  Apr  22 [Thu]  190.9   -0.9   11.1    98.1
  2004  Apr  24 [Sat]  187.2   -0.9   16.4    96.0
  2004  Apr  26 [Mon]  183.5   -0.9   21.6    93.0



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

----
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