[amsat-bb] AO-40 power problems -- a telemetry study

[John Mock <kd6pag@xxxxxxx>]

I've been looking at AO-40 telemetry for the purposes on understanding the
Earth and Sun sensors for use on Project EAGLE.  Given recent events, i had
a look at some of the power sensors and saved lots of plots for further
examination.  What i've come up with so far is summarized on the following
URL:
	http://www.qsl.net/kd6pag/AO-40/PowerAnomoly.html

The first two plots therein show the last two orbits, including the attempt
to turn the auxillary batteries back on before everything went into safety
shut down at approximately MA=120 (judging from the plots).

Looking back at one month intervals from the event in question shows that
there's been alot of fluctation in main battery voltage for a couple of
months, starting about a week before Samhein/Halloween (e.g. the point
half-way between the Autumnal Equinox and the Winter Solstice).  Before
that, main battery voltage appears to have been stable for several months.
Some of the fluctation in the past week or two have looked fairly dramatic
to me, but i have no idea what nominal is.

By sheer luck, i came across the end of a previous period of main battery
functuation which might have been similar, ending with the main battery
voltage aburptly going from about 25.5V to almost 28V between roughtly
MA=135 and MA=160, after a long period of fluctuation.  This was happened
quite co-incidentally on 26 April 1993, nine months prior our recent event.
I still need to look more carefully at this data and see if i can determine
when the beginning of the earlier period of main battery fluctation actually
began, etc.

I don't know how much this had to do with the very low power shutdown which
occured last week, but perhaps this might be at least of interest to those
working on AO-40.

I've saved about a year of plots of a few power-related sensors on-line, 
which can be queried via:

	http://www.qsl.net/kd6pag/AO-40/PowerAnomoly.html#forms

This also includes two solar panel temperature sensors, which may provide 
a clue to when the satellite is actually being illuminated.

Sorry, the values ploted are raw sensor values, due to limitations in the
PERL plotting software.  There is a link to the page which shows the actual
sensor values for that orbit, however my telemetry archive currently lives 
on my laptop and thus that information may not always be accessible (but 
the plots should be).  This is not being run on a public server, so please
don't publish the resultant URLs from your on-line queries.

I hope this is at least of interest.  Best of luck to the recover team!

				-- KD6PAG
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