[amsat-bb] PSAT digipeating and Position Knowledge

Robert Bruninga bruninga at usna.edu
Fri Jun 19 15:36:43 UTC 2015

We successfully sent commands to re-write PSAT EPROM values to correct the
Orbit clock.  It worked.  Over a few days, we will fine tune the value and
be able to turn on PSAT Position reporting.

In looking at the orbit timing, we also came up with these factoids.

PSAT passes are almost exacrtly 15 minutes earlier every day. (14.7 minutes

And the time between orbits is almost exactly 100 minutes (1 hour 40

You can use these to plan your “free time”… without needin’ no stinkin’

Bob, Wb4APR

An aging Luddite

*From:* Robert Bruninga [mailto:bruninga at usna.edu]
*Sent:* Thursday, June 18, 2015 7:34 AM
*To:* amsat-bb at amsat.org
*Cc:* bruninga at usna.edu
*Subject:* PSAT digipeating and Position Knowledge

PSAT continues to work well, both APRS and PSK31.  The downlink capture on
the PCSAT.APRS.ORG page captures most PSAT packets, but does not capture
any digipeated users if they use the ARISS path.  Although PSAT supports
the VIA ARISS alias so that users can use both ISS and PSAT without
changing parameters the FINDU page does not recognize it.

At this point it is unclear what paths that FINDU recognizes.

These paths are supposed to be digipeated by PSAT:





Here is what we know:

ARISS is not recognized by FINDU.

We are not sure if FINDU recognizes APRSAT

We are not sure if PSAT recognizes PSAT

We have seen VIA WIDEn-N work on FINDU

We have been busy with deadlines on our next satellite, but yesterday we
figured a workaround on the PSAT ORBIT and MA clock.  This morning we sent
the commands and will be watching to see if they work.  If they did, then
PSAT will be able to know where it is, and then we can activate its APRS
POSITION packets plus individual beacons over individual continents.

Although the S#OOOMM… telemetry was supposed to be ORBIT number and MINUTE
of that orbit, the clock is totally off.  SO instead of going from 0 to 95
minutes per orbit, the actual count is more like 0-61 minutes per orbit.
So, if this works, then MM is not real minutes, but is a number between 00
to 61 on every orbit.  And 0 should be when the satellite crosses the
equator (actually 5 South latitude)  on every orbit northbound.

Once we get that under control, then PSAT will know where it is, and it
will be able to report its own position.  And we can activate its attitude
control, and we can activate different bulletins over each continent.


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