[amsat-bb] Re: Newbie question about AO-07
Auke de Jong
sparkycivic at shaw.ca
Fri Oct 31 20:04:28 PDT 2008
AO-7 happens to be in "permenantly sun-lit" conditions. I believe this
current period to last fairly long, but I forget now just how much longer,
but I think it's on the order of months. AO-7 has a time counter that
controls the mode A/B toggle therfore, it will change modes every 24 hours
starting at whatever moment the last sun-rise for the spacecraft
was(sometime in early August), and always starting in mode-B.
You can look at the logs on http://www.planetemily.com/ao7/main.php , to
figure out what mode the satellite was most recently used. I just read the
log, and found that the A/B changeover time, these days, is approximately
20:55 UTC. It's likely that the last sunrise AO-7 experienced must have
been about 20:55 on Aug 5.
When not in continuous sunlight, it mostly stays in mode-B, never making it
the full 24 hours to switch, since the eclipse happens every orbit, or about
1 hour 55 min, for some portion of those orbits.
I'm always impressed when I think about the like-a-rock reliability this old
craft has shown! I look forward to perhaps a future craft being launched
that is built using the old-style analog hardware prevalent in this old
bird.. Something retro, maybe with the old hand-laid harnesses, a clever
battery-failsafe scheme, and a dose of enhanced-performance components, it
might just last forever!
----- Original Message -----
From: "Mark Lunday, WD4ELG" <mlunday at nc.rr.com>
To: <amsat-bb at amsat.org>
Sent: Friday, October 31, 2008 7:04 PM
Subject: [amsat-bb] Newbie question about AO-07
> For some reason, I cannot seem to find info which indicates the mode for
> pass...mode A or B. I usually figure it out after listening on 145
> and not hearing anything then going to the 29 MHz downlink. Once, I even
> heard my downlink on 29.45 MHz at the start of the pass only to hear it
> stop. Was not sure what happened until I started tuning around and
> discovered the bird had SWITCHED from mode A to mode B in the middle of
> pass! So my question is...other than trial and error or listening for the
> beacons (which won't help if the bird switches during the pass), is there
> any pattern or location of information for the prediction of the mode?
> Thanks, as I am thrilled each time I can get through this oldie-but-goodie
> with 5 watts on CW. What a blast!
> An additional question since the batteries have long ceased to function on
> AO-7, it only works during sunlight passes. Somebody mentioned that this
> will happen less and less as we get close to winter solstice. Is this
> because AO7 is in a northerly LEO orbit? If it passes in the southern
> hemisphere, would it not have MORE available online time? I see
> http://planetemily.com/ao7/Eclipse.php but it's not a predictor for
> 2008 (and I am not sure I understand it anyway). Should I just set
> Orbitron/HRD for AO7 "in sunlight/illumination" only option?
> Mark Lunday
> wd4elg at arrl.net
> Sent via AMSAT-BB at amsat.org. Opinions expressed are those of the author.
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