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Re: AO-07 PARADOX?



Tom, I have not been able to check it every pass, but the times I have
listened, I have never heard it when it was in the dark.  Additionally, I
have watched it pass from darkness into sunlight and did not hear it come
on even though it was at a pretty high elevation here.  It did set however
about 5 minutes later.  Perhaps it takes a bit to get up and running after
it goes into sunlight, or perhaps it happened to wake up in mode A that
particular time.

"Tom Clark (W3IWI)" wrote:
> 
> Luc -- you asked
> 
> > The last news on AO-07 was that the solar cell come shorted
> > due to battery weekness, How is it possible
> > to solar cell to unshorted themself and let battery recharged
> > after so many years?
> 
> A standard mode for a NiCd battery to fail is for a cell to become short
> circuited. When AO-7 died years ago, the telemetry showed that several cells
> became shorted, and then the satellite went silent. At the time the
> spacecraft was running hot (about 40 C) and we felt that the cells failed in
> the "cooked" mode.
> 
> Now we speculate that (at least) one of the shorted cells has acted like a
> fuse, becoming an open circuit. If this is the case, then the satellite is
> running only on solar power, and then only in sunlight.
> 
> If this is true, then the satellite turns itself on/off each orbit as it
> enters sunlight. The mode it chooses to select is probably random.
> 
> It would be interesting if the folks on AMSAT-BB would confirm that the
> satellite only operates in sunlight. Here is a simple way to know if the
> satellite is in sunlight: Look at a graphical view of the visibility circle
> on a map that also includes the sunrise/sunset line. If any part of the
> coverage circle lies inside the daylight area, then the satellite sees the
> sun.
> 
> Here I used IT and loaded the KEPS that have appeared on AMSAT-BB. I select
> [2] Map View and the AO-7 satellite. To see the satellite move rapidly hit
> [F] and then use the [space bar] to toggle fast time on/off. Then you can
> read the time that the satellite sees the sun or is eclipsed.
> 
> For any of the AMSAT-BB folks: do you have ANY instance of being able to
> hear/work AO-7 when it is dark?
> 
> 73 de Tom, W3IWI
> 
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-- 
73, Roy -- W0SL

E-Mail: rdwelch@swbell.net
Home Page: http://home.swbell.net/rdwelch
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