[amsat-bb] STP questions

[Jim White <jim@xxxxxxxxxxxxxxxxxxxxx>]

Phil,

A some questions and clarifications regarding your proposed STP.

RUDAK TLM is AX.25 UI frames.  There is no error check information within 
the data portion of the frame.  A TNC strips off the AX.25 CRC and 
typically provides a KISS wrapped frame to the computer.  Would the 
spacecraft telemetry block include the KISS wrapper?  I assume yes.

Some satellites may send TLM frames as often as every 2 or 3 seconds.  Is 
each frame a separate messages in STP, proceeded by the full set header 
lines?  I assume yes.

Many existing 400 bps PSK demods send only 512 bytes of the AO-40 TLM to 
the computer so no CRC or other error checking is available.  Would the 
sync vector still be included in the spacecraft telemetry block?  I assume yes.

One might tentatively suggest the following Source definitions for RUDAK in 
AO-40:
amsat.ao-40.rudaka.standard
amsat.ao-40.rudakb.standard

However, it is possible for either rudak processor (a or b) to send 
independent data streams on as many as 7 different downlink frequencies, or 
even alternately on the same frequency.  For example when a 153k6 downlink 
is activated the data stream may contain the full TLM data set while the 
9k6 downlink would be constrained to a small subset.  Should that be 
implemented how would we define the Source?  Should there be a another 
layer under the subsystem name?  The frequency may not always identify the 
sub-subsystem either because they send on the same frequency or because of 
Doppler (recognizing the frequency header should be the nominal 
frequency).  It would be possible to identify the sub-subsystem by 
examining the callsigns but that would require decoding the spacecraft 
telemetry block which seems to corrupt the concept of the header.  Thoughts?

Jim
jim@coloradosatellite.com
wd0e@amsat.org

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