Op 18-8-2011 16:08, Andrew Glasbrenner schreef:
> 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
Has anyone ever considered piggybacking on a geosat in a simular way the
rs11 to 13 did?
Sure you would need a very good lobbyist to get a ride with a multi
milion dollar broadcast sat and it would only see one continent but it
will give that continent 24/7 coverage, using 3 cm as downlink it would
give pleny bandwith for all kinds of experiments and if you can use the
host sat's powerbus there would also be no power restrictions.
73 Andre PE1RDW
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