Noticed a funny scenario today. All afternoon I had 7-8 satellites locked (On my GT31) then at 5.00pm DST (Sydney time) things started to go bad, by 5.15pm I was down to only 5 and it stayed that way for the next 30 minutes before improving again. It didn't bother me as 5 is still enough to produce doppler speeds. Unfortunately a friend was 50 minutes into an hour attempt when his GW60 dropped to 4 satellites, thus producing invalid doppler data.
I looked at a few other tracks from KA72 and saw a similar thing.
Did anybody else notice this?

Is there a way to look at how many satellites should have been in view at that time?