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Re: DSP software on Sunsat SO-35



On Sun, 13 Feb 2000, Johann Lochner wrote:

> Sunsat is equipped with a high resolution imager capable of filling 
> the 64 MB ramtray in a matter of seconds.  However, because of the 
> failed 40 Mbit/s S-band downlink, we are forced to download data at 
> only 9.6 kbit/s.  With about 40 minutes of useful download time per 
> day this is getting extremely boring (not to mention the frustration 
> for not being able to capture such wonderful images more often).

Why be limited to just 40 minutes a day?  When you could have 6 hours
or more?  With just four  people in the USA, one in the UK,
one in Australia, one in Hawaii, one in Japan  and a few other places with
simple Kenwood THD7 walkie-talkies and their build-in 9600 baud TNC's 
we can provide as much as 6 hours a day or more of downlink
connectivity to our amateur satellites.... Its trivial to 
couple the output of the walkietalkie to the internet so that any
satellite operator can get live feeds from other hams anywhere on earth
that the internet goes.

Our site is live and feeding a TELNET port 24 hours a day of every 9600
baud amateur satellite that comes over the East coast of the USA.  I can
privately give you the TELNET address (since it is a single user IP
address).  And my total investment is an HT and and old dos PC running
APRStk for auto doppler tuning.  Anyone with the Kenwood or other
9600 baud receive set up can do the same thing (with the right software).

This is how we feed all the worldwide APRS data "live" everywhere.  We
tried to get others to join us and in 1996 through 1998, we had 3
stations, ours, and one in Madrid and one in Taiwan providing such
continuous feeds for the MIR downlink.

The only thing the satelite needs to do is stream the data in UI frames
instead of a connected protocol.  Then just collect it and munge it back
together as it dribbles in from all over.

Similarly, we could VASTLY improve the downlinks of bulk files from our
existing pacsats if we didnt try to download the same files to every
ground station, but just let everyone pool their captures together.  This
would permit a 10 fold improvement in data throughput or more... (unless
someone is already doing this)...

Yes, the PACSAT PROTOCOL is very effecient, but it still is delivering
identical copies of every single byte in every different footprint
worldwide.  Yes this IS REQUIRED for isolated stations without internet
connectivity.  But if we only had 4 stations in the USA "pooling" their
downlink captures, then you would have a 99.99% chance of getting every
file in only ONE transmission (assuming they get 90% each normally)

Linking ground stations by the internet is a trememdous bandwidth
multiplier which we need to take advantage of in the Amateur Satellite
Service.. 

de WB4APR, Bob   (US Naval Academy Satellite Lab)

All the pieces are there (sort of)...

Kenwood plug-n-play 9600 baud data radios with built in TNC's
WinAPRS and APRS+SA and others automatically feed all UI packets to IP
Tracking programs abound...

(Sorry, my configuration is probbly NOT reproducible because I am using
a BASIC program on a DOS machine feeding a single RS-232 hardware Remote
Terminal LAN which just happens to give an IP address to each
dumb-terminal...

Anyway, just a thought... (and of course, I could have completely
missunderstood your posting, and if so, ignore this..<grin>)


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