Re: [amsat-bb] AMSAT has a SECRET!

[Douglas Braun NA1DB <doug@xxxxxxxxxxxxx>]

At 04:03 PM 6/2/01 , John Stephensen, KD6OZH wrote:
>Wideband modes will work fine on LEOs at 2.4 GHz. UoS has 1 MBPS downlinks
>on S-band.


But what sort of antenna do you need to capture such a large-bandwidth
signal?

I stumbled across the web pages for the soon-to-be-launched HESSI satellite.
This satellite will be in a 600 km high orbit, and will have a 5-watt
transmitter on 2215 MHz, with a 5 MBPS data rate.  To receive this, their 
ground station needs a 11-meter dish!  Check out:
http://hessi.ssl.berkeley.edu/ground_systems/Gif/antenna_install_79.jpg
This antenna is speced to point with 0.05 degrees of accuracy,
while slewing fast enough to track a LEO satellite!

Maybe this is overkill for their typical operating conditions, but
it is WAY out of the amateur league.

BTW, the project Web site http://hessi.ssl.berkeley.edu/index.html
is PACKED with detailed technical descriptions of the spacecraft,
the ground station, the software, etc., etc.

(They use a descendant of SatTrack.)

Doug
NA1DB



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