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RE: AO-07 PARADOX?



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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