[amsat-bb] Re: NO-44 and ISS

Bob Bruninga bruninga at usna.edu
Sun Apr 12 05:25:53 PDT 2009

> I remember that you asked us NOT to
> digipeat via W3ADO-1. From time to time 
> I listen to NO-44 and note that the 
> batteries pretty weak.  Only some 
> packets (from always the same European 
> station) come through...

Good question.  We ask people to never use automatic unattended beacons via W3ADO-1.  

Especially when we are trying to recover PCSAT (3 times a year in the winter time), then we need every possible mA of current to try to get command link.  Then we make many postings asking users to not digipeat via W3ADO-1.

But when PCSAT is mostly dead, the command station does not try to recover, so human attended users may use it if they want.   But everyone must remember that PCSAT is a PACKET digipeaterr and it needs TEN times the current during TX than it does for the receiver and CPU.  This is why you can hear PCSAT attempt to TX a packet, but it cannot even maintain that current for even 1 second, so the packets die before the end of the second and it cannot be decoded.

AND that packet attempt has consumed TEN times the current it needs to operate.  So the only successful packets will be AFTER a long period of silence.  That is why we ask that ONLY human operators MANUALLY transmit a packet ONLY when they think they have a chance at a digipeat.  It is a game of skill with one bullet.  Not a game of shotguns...

EACH attempt at a packet kills the spacecraft for 10 times longer and prevents others from using it.  So we do not want any unattended periodic beacons from users that KILL the satellite when they are not even there to listen.

The problem is, that there is only enough solar energy on a good noon-time pass for maybe 2 or 3 packets TOTAL during the pass.  And that is only if they get lucky and transmit after a long period of silence when no one else attempts it.

Of course, asking everyone to share (not transmit) so that one person can get lucky (and transmit) is a hard problem in human nature.  And especially over densly populated areas like Europe.  See the "tragedy of the commons".

So, yes it is ok.  But no one will be successful if everyone tries.

Hope that helps.

Bob, Wb4APR

>-----Ursprüngliche Nachricht-----
>Auftrag von Bob Bruninga 
> It is easy to see.  Each of these two satellites 
> have an automated APRS web page where you 
> can literally *see* the activity up to date.  
> You can see the last packet heard by anyone, 
> and you can see who heard it.  And you can see
> whree they are.
> For ISS, see www.ariss.net
> For NO-44 see http://pcsat.aprs.org
> Each packet heard is shown, sorted by how 
> long ago it was heard.  If you click on 
> the station, you can see what sat-gate heard 
> it an injected it into the system.  The SATgate 
> is the callsign immediately after the QAO or 
> QAR or QAS construct.  You can then see where 
> they are by entering their call into the
> http://map.findu.com/CALL
>Looking at the ARISS page right now at 9:27 PM Mountain time, you can see
>that about 8 stations have been heard today (about 5 or 6 hours ago) and
>that those are the only ones that have been heard then since 9 days ago.  So
>it looks like you might be lucky.  This tells us that the crew on ISS did
>turn on packet mode about 6 hours ago, and 10 people got through.  ANd this
>is the first time it has been on in 9 days.
>Now, click on KN6NS-1 for example, and you can see in his packet:
>That he was digipeated by RS0ISS-4* (the ISS callsign) and his packet was
>heard by KD8CAO-6 and injected into the APRS internet where this web page
>then saw it and put it on this web page.  The ISS signal is strong.  It is
>black and white.  If it is ON, then you will hear it on ANY base station
>antenna.  When it is off, no one will hear it.
>Now, it has been 5 hours since the last station heard, but this does not
>mean it is back off.  Just look at the orbit.  Where is ISS now and where
>has it been for the last 5 hours.  Maybe it has not been over any active ham
>country.  So it -could- still be on.
>BUT on the other hand.  If you can -see- on your tracking program that the
>ISS has passed over the USA or Europe in the last few hours, and you do
>-not- see any packets on the web page, then it is safe to conclude that the
>system is presently off.
>Similarly, you can look at http://pcsat.aprs.org
>and see that about 8 statiosn were heard today,
>7 a day ago and so on, on down.  But PCSAT (NO44) is not black and white:
>1) it is totally dead in the dark
>2) it is barely alive in the light
>3) it is ONLY strong enough to complete a  1 second user packet relay
>usually when it passes right under the sun. 
>4) and only in the northern hemisphere where the best solar panels face
>5) and it is 10 times weaker than ISS so you will only hear it if it is high
>in the sky at your location.
>6) therefore the only successful stations are usually under the satellite
>about mid-day.  And there is a two  month or so cycle as to where that is
>occuring on any given day...
>7) and these will not get to the web page, unless there is also a satgate in
>the footprint to relay it to the APRS internet and hence to that web page.
>SO, those two web pages give you the global bird's eye view live as to what
>is happening with those birds.  sleuthing out this info can give you a good
>feel what is going on.
>Good luck.
>'At least now you know the ISS does work.  Or at least it did 5 hours ago
>Bob, Wb4APR

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