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Re: PCsat Critical



PCsat recovered:

After working 15 out of the last 22 passes over 36 hours as of 1200z this
morning we finally got PCsat back into a positive power budget (and
negative sleep budget for sysop).  But we think we got it.  But we must
keep all user access OFF for the time being.

ALthough we have been doing OK with our power bueget in max eclipse for a
few weeks, this  problem snuck up on us as follows (we think)...

1) The phase of our commanding has been in the AM (local) as the passes
occur earlier and earlier.  But as of this week, no passes are occuring
during morning wake hours, so yesterday I began to command from home in
the late evening when the first passes occur (In hind-sight, this is
when PCsat is going INTO eclipse and so apparently, subsequent resets in
eclipse cancel my low-power commands back to SAFE mode)

2) PCsat is now beginning to pass over the USA and Europe in the late
evening hours (prime time for users) but this is also the worst time for
PCsat in the middle of eclipse.  Thus we are seeing a change in peak user
demand relative to the phase of our eclipses and the phases of our
commanding, and the phases of sleeping and waking.

3) With the experimental -Z panel out, we may be in a phase that has the
-Z panel (north seeking) facing the sun more often when we are in sun, and
thus we may not be getting the same amount of charge that we used to.

But now we learned these lessons, as well as the lesson of how severly
damaging just a few user CONNECT attempts are to our power budget.  We are
going to leave user access off for the next 48 hours to try to get to full
charge so we can do the LED's test tomorrow night.

Thanks!
de WB4APR, Bob



Thu, 15 Nov 2001, Bob Bruninga wrote:

> PCsat critical.
> The good news is that at about 0152z on 16 Nov we did get connected and
> did get both UHF receivers  off and both redundant transmitters isolated,
> and the DIGI turned off for maximum conservation of critical power.
> Battery volts were down to 1.0 volts per cell but picked up a bit.
>
> The bad news is that when we disconnected the command channel, an
> individual decided to try his hand at it.  The ensuing 10 retries of the
> PCsat command channel to this individual at 4 lines a piece (40 lines) ran
> the batteries down to a damaging .84 volts per cell and will probably
> cause a reset and loss of all settings during the remainder of the
> eclipse..
>
> Users must understand that the health of PCsat depends on all of us.  It
> is a simple design and does not have all the protections that a good
> satellite design should have.  Its mission is as a UI digipeater.  There
> is no reason for any user at any time to ever attempt a CONNECTION either
> VIA PCsat or TO any of the callsigns on PCsat.  It is for UI packets only.
> CONNECTIONS are a tremendous waste of very limited  power.  Help us to get
> this word out to HAM's worldwide...
>
> PCsat runs on a simple set of 12 AA nicads like in your HT.  But when it
> goes to SAFE mode for maximum probablility of command, it turns on dual
> redundant receivers and dual redundant transmitters.  The backup receivers
> consume more than twice the receiver load and the transmitters in this
> mode draw a whopping 12 Watts for every packet.  When this happens there
> are 3 things that need to happen soon:
>
> 1) The command station must connect and turn off unnecessary receivers (if
> the primaries are working) and Isolate the transmitters if they are
> working.
>
> 2) Users should eliminate any additional load on the transmitters, by
> ceasing all UI transmissions VIA PCsat or any of its callsigns.
>
> 3) Users must NEVER attempt any "CONNECTIONS" either TO or VIA PCsat at
> any time, safe-mode or not, ever.  Retries and ACKS are killers and can
> quintuple the load on PCsat far over its power budget.  THis forces SAFE
> mode and we are back to square one again...
>
> We have been trying to teach users that typical CONNECTIONS are *bad* for
> the last  10 years of MIR, SHuttle and ISS operations.  But they had LOTS
> of power.  PCsat doesn't and cannot survive the resultant loads.
>
> I am sharing this with everyone, because PCsat is a simple satellite, easy
> to understand since it is no different from your TNC in your shack.  The
> only difference is that we can never ever get back to "fix" it if
> anything goes wrong.  So help us by operating via PCsat only in accordance
> with recommended operating procedures and it should last...
>
> Thanks!
> de WB4APR, Bob
>
> On Thu, 15 Nov 2001, Bob Bruninga wrote:
>
> > Sorry PCsat users,
> > On the next opportunity I am going to have to turn digi OFF.  Seems like
> > on every pass over the northern hemisphere in the  prime-time evening
> > hours while in eclipse, PCsat is running outta juice  before it gets back
> > to sunlight..
> >
> > I want to max conserve batteries until Saturday nights LED test.  So
> > please, no operations for the next 2 days (or more) and in any case, lets
> > get the word out that if you ever see 11111111 in the telemetry and
> > unless otherwise told, do NOT use PCsat.
> >
> > de WB4APR@amsat.org, Bob
> >
> > PCsat WEB  page     http://www.ew.usna.edu/~bruninga/pcsat.html
> >
> > ----
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> >
>
> de WB4APR@amsat.org, Bob
>
> PCsat WEB  page     http://www.ew.usna.edu/~bruninga/pcsat.html
> ISS-APRS FAQ:       http://www.ew.usna.edu/~bruninga/iss-faq.html
> CUBESAT Designs     http://www.ew.usna.edu/~bruninga/cubesat.html
> APRS LIVE pages     http://www.ew.usna.edu/~bruninga/aprs.html
> APRS SATELLITES     http://www.ew.usna.edu/~bruninga/astars.html
> MIM/Mic-E/Mic-Lite  http://www.toad.net/~wclement/bruninga/mic-lite.html
>
> ----
> Via the amsat-bb mailing list at AMSAT.ORG courtesy of AMSAT-NA.
> To unsubscribe, send "unsubscribe amsat-bb" to Majordomo@amsat.org
>

de WB4APR@amsat.org, Bob

PCsat WEB  page     http://www.ew.usna.edu/~bruninga/pcsat.html
ISS-APRS FAQ:       http://www.ew.usna.edu/~bruninga/iss-faq.html
CUBESAT Designs     http://www.ew.usna.edu/~bruninga/cubesat.html
APRS LIVE pages     http://www.ew.usna.edu/~bruninga/aprs.html
APRS SATELLITES     http://www.ew.usna.edu/~bruninga/astars.html
MIM/Mic-E/Mic-Lite  http://www.toad.net/~wclement/bruninga/mic-lite.html



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