>From what I have read that is published, the DOD Colony II 3u cubesats are 3 >axis controlled and pointable to within a degree or something close to that. >As Bob pointed out this isn't a big help for antenna pointing for multiuser >LEO sats, but when you read the power production the Colony II sats have, >you'll see the application in a HEO orbit. I believe a 3u in HEO with this >ability would be an affordable, usuable satellite for AMSAT to launch if we >could duplicate the Colony sats abilities.
73, Drew KO4MA/p at the corner of No and Where, Oklahoma Sent from my iPhone On Aug 18, 2011, at 7:47 AM, "Bob Bruninga" <bruni...@usna.edu> wrote: > [Using attitude control]... > >> We could mount microwave antennas on a nadir-facing >> surface and provide consistent, predictable, strong, >> wideband signals to ground stations during a pass. > > The problem with LEO satellites is that a nadir facing antenna does give > great gain directly overhead ground stations, but only for about the center > 2 minutes of only the one direct overhead pass a day. The problem with > facing antennas "down" on a LEO satellite is that 90% of the users are not > "under it", but to the side of it. > > For example, lets say that we put relatively high gain antennas facing down > giving about a 45 degree antenna pattern (say around 10 dB). Now looking at > the total time that ARISSat is above 45 degrees, turns out to be about 3 > minutes a day or less than 10% of all the time it is in view to any one > ground station. > > But as you say, it is a great advantage if the objective is to provide a 2 > minute comm. window to anyone on the planet once a day, then such a design > does give as much as 16 dB or so advantage over an omni antenna on a > satellite. > > Anyway, just a thought. > Bob, WB4APR > > > _______________________________________________ > Sent via AMSAT-BB@amsat.org. Opinions expressed are those of the author. > Not an AMSAT-NA member? Join now to support the amateur satellite program! > Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb _______________________________________________ Sent via AMSAT-BB@amsat.org. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
