[amsat-bb] RE: AO-40 E block question

["Stacey E. Mills" <w4sm@xxxxxxxxxx>]

Jim Walls said:

>Hi all,
>     I was watching the AO-40 telemetry for a while this morning, and
>noticed something that made me ask why?  I know that E blocks are events
>that have happened at some point in the past. What I was noticing was
>that the same block was being sent over and over and over.

Nope.  If you look at what you posted these are two distinct blocks, the
"8" event block from 2001-05-13 and the "C" event block from 2001-9-15.

E HI, THIS IS AMSAT OSCAR-40 2001-05-13 04:12:10 #015D
EVENT #0008

E HI, THIS IS AMSAT OSCAR-40 2001-09-15 17:51:08 #02FD
EVENT #000C

There is a 16 event circular buffer which cycles through the most recent 16 
events.  Currently events don't happen very often, which is good!  During 
the last years of AO-13's life there were multiple (often many) events per 
day.  Having a 16 block buffer is prudent.

>Looking at
>the raw data (quick look) and the decoded E block telemetry it looked
>like exactly the same block was being transmitted as many as 5 times in
>a row (with no othere blocks being sent), and it was data that was over
>a year old.

No, see above.  There is a set of 16.

[snip]

>Since the beacon has a rather fixed (and low speed)
>capability, I would think it does not make sense to keep transmitting E
>blocks that have been successfully decoded here on earth and archived.
>Or is there no way to flush old events from the satellite's memory so it
>stops sending them?

The telemetry stream can be changed to send only A blocks, only E blocks or 
whatever. However, things don't happen that fast in space.  What would you 
send instead of the E-blocks?  As it is, we get an A-block every ~23 
seconds.  That's fast enough.  If we need more we can turn the E-blocks off 
for an hour at a time, but there is no reason not to leave things as they 
are.  When the next event comes it will be available without special command.



-- 
  ________________________________________________________________________
  Stacey E. Mills, W4SM    WWW:    http://www.cstone.net/~w4sm/ham1.html
    Charlottesville, VA     PGP key: http://www.cstone.net/~w4sm/key
  ________________________________________________________________________

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