[amsat-bb] AO7 in Mode B

K4FEG K4FEG at k4feg.com
Sun Jun 16 12:43:14 PDT 2013

Thanks everyone!!

Thanks everyone for the reports on AO7 and it being in Mode B.

I think it should be in Mode B for a few more weeks so Field Day should 
have it in Mode B the entire duration of Field Day.

We are in the middle of the Eclipse Cycle, by all standard means of 
calculating, we (the Earth), are near the furthest distance from the Sun 
and the Southern Hemisphere is quickly approaching their "Winter" 
Equinox (shortest daylight period of the year), so this would be the 
time when AO7 would have the least amount of exposure to the Sun during 
passes over Antarctica. I know there are programs that will tell you 
when a satellite is "in the Sun" or not and SATPC32 seems to do a better 
than average job of predicting when an eclipse period is occurring.

There have been questions as to whether or not a program like SATPC32 is 
calculating the solar position based on ground track or actual satellite 
position in orbit, I have not reached out to find out the method of 
calculations but based on how AO7 has reacted to even the briefest of 
eclipse's as predicted by SATPC32, I suspect the relationship of the 
satellite to the Sun is being predicted based on the actual satellite 
position in orbit and not based on ground track. When AO7 first started 
its "Zero Voltage Reset" and ceased switching modes back on May 21st, 
the eclipse period that triggered the reset was only estimated to be 
about 15 to 20 seconds. Reports that I have received from an operator in 
New Zealand, who has access to the satellite at times when it is heading 
into eclipse and coming out of eclipse, has stated that the satellite 
merely "fades" out and then "fades" back in when it comes out of the 
eclipse. Based on research about the construction of AO7, it has a 
better than needed solar array, from that era in which it was designed 
and built, and appears to suffer no ill effects from the "fading 
voltage" as the satellite loses the sunlight.

If the Eclipse Cycle holds true to the predictions and continues to 
react as we have see it do so for the last almost 4 weeks, it should 
continue to do what I am calling "Zero Voltage Reset" until it is in 
continuous Sun over Antarctica, which will not occur for several more weeks.

This is one of the reasons I have been studying the reactions of AO7 
during this period, the way the satellite was designed gave an outline 
of how it should react coming out of eclipse, with no on-board battery 
system, but to my knowledge there has not been a case study, trying to 
accurately track how the satellite will react. I am just trying to 
collect data that will help in trying to predict how the satellite may 
react when the next Eclipse Cycle occurs. Perhaps during future eclipse 
events we can have a much more scientific study of the "Grand Old Lady" 
of satellites, AO7.

If nothing else I think we can learn much from the how this satellite 
was built and has been "reborn" to help serve the satellite community!

My hat is off to the design team for building one tough bird! Job Well Done!

Thank you everyone who sends me email updates about their observations. 
I hope I am not boring people with my current obsession of AO7, but I 
like the old bird!

GGHQ: EM55aj84ta

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