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Re: 9600baud questions....



 
> I don't think I've ever had explained to me what people do, exactly, 
> with the packet satellites?

Very briefly, Pacsat satellites act essentially as fileservers in space.
Groundstations may upload files to the satellite specifying a particular
destination address (groundstation callsign).  Groundstation software
requests and reads directory information from the satellite and decides
what files it needs to download.  Such files may include those addressed
to "ALL" or your callsign.

Anyone within the footprint of the satellite may capture files and
directory information broadcast by the satellite.  Pacsat satellites
also interperse their file and directory transmissions with telemetry
and status information, and generally create some of their own files
for download.  These files include images of the earth taken by CCD
cameras, log files showing who's been using the satellite, and other
related information.

Uploads and downloads may take place over numerous passes making it
possible to transfer large files even though a Pacsat satellite may
only remain in range for about 17 minutes.  For example, my first AO-16
download was of an 80 kilobyte JPG image uploaded by a station in Italy.
AO-16, by the way, operates at 1200 baud.  :-)
 
The only digital communication satellites that operate in a manner that
resembles the operation of a packet radio BBS are FO-20 and FO-29 when in
Mode JD.  All the others (AO-16, LO-19, UO-22, KO-23, KO-25) utilize the
FTL0 Pacsat Broadcast Protocol exhibiting the features described above.
WO-18 will be added to this list once its primary mission of taking earth
imagery is exhausted.  IO-26 will also be added once its OBC software has
been uploaded.

Most of the messages carried through Pacsat satellites are person-to-person
messages similar to e-mail messages, but without the privacy.  Occasional
questions, news bulletins, and Keplerian data files are addressed to "ALL"
and are downloaded by all stations working the satellite.

The 1200 baud AO-16 and LO-19 satellites can accept simultaneous uploads on
as many as four uplink frequencies and place as many as 10 groundstations in
their broadcast queues.  The more heavily used 9600 baud satellites (UO-22,
KO-23, and KO-25) have queues that service the requests for as many as 20
stations.

AO-16 also has its digipeat function turned on, although it is seldom used
since there is little practical use of digipeating packets off a satellite
in space when the fileserver serves a much better function.


73, de John, KD2BD

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-=-=-=-=-=-=-=-=-=-=-=-=- John A. Magliacane, KD2BD -=-=-=-=-=-=-=-=-=-=-=-=-
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