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!
73's Auke
----- Original Message ----- From: "Mark Lunday, WD4ELG" mlunday@nc.rr.com To: amsat-bb@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 the pass...mode A or B. I usually figure it out after listening on 145 downlink 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 the 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 November 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 wd4elg@arrl.net http://wd4elg.net
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