22 March 2002
From: WB4APR
To:   AMSAT/APRS

Subject:   PCsat: it ain't over!

I have been so buried in the round-the-clock keep-alive effort and seeing 
no improvement, and seeing only a worsening eclipse ratio, it seemed like 
the end was at hand.  So having thrown in the towel, I relaxed today and 
had some time to look for some other second order effects...

DUH!  The other biggest factor is that even though Eclipses get worse over
the next week, I realized the solar angle on the +Z face is improving
every day due to precession.  And since +Z is our best face, this could
make a difference.  After an hour in a dark room with a light bulb shining
at a globe and going through dozens of predictions with Instantrack and
gyrations with a dice with -Z pointed at the earths magnetic vector, the
answer is YES!

With 3.2 degrees west precession per day, this means that in 28 days we go
from worst case to best case on the +Z!  Looking at the magnetic vector
relative to the sun my best guestimate is that we will get Maximum +Z on 7
April and working backwards means we had 0 contribution from the +Z panel
on 10 March.... Exactly the day when this problem began!

Thus, as of today we are exactly 40% up the cosine curve towards best
+Z angle.  And +Z contributes 1.5 times as much as any other panel.  So
our peak charging current will be up 2.5 times more on 7 April than it was
on 7 March.  This is a BIG factor!

In fact, it is much bigger than the small worsening of eclipse we will see
before it begins to get better too... So, I'm now betting that +Z is going
to bring us out of this real soon now... and we will be back in the saddle
again! (unless I goofed somewhere)...

So, if I can put the horses back in the barn for this weekend, we might
just make it through this...  The Fat lady ain't sung yet...

Bob, WB4APR

yes, I konw that there are all kinds of programs and models that could
have predicted this, but we don't have anyone working on PCsat but me, and
I havent had the time...  (if someone has the time and the inclination,
such a model of our magnetic stabilization with max contribution from the
+Z panel and 0 from the -Z should be very easy to predict).  In fact, I
fear that someone did send it to me 5 months ago, but in 4000+ emails we
lost it...