[amsat-bb] One satellite or many? EmComm
bruninga at usna.edu
Mon Dec 17 18:47:58 PST 2007
I am 100% in support of P4. So this message is not related to that topic...
But I am excited about this Emergency Communications mission that AMSAT-NA is investigating as a means of ensuring our long term relevance. Emergency Preparednes and communications to me has always been a prime motivator in Ham radio.
That said (and without any intent to distract from P4), my vision has beem to promote a low rate LEO satellite emergency message capability that anyone can hit using just what they already have. IE, packet messages on the satellite frequency of 145.825. We have been trying to gather together a constellation of as many LEO satellits as we can get (up to 10 or so), all acting as digipeaters on 145.825 so that we have nearly continuous coverage everywhere. Meaning, at any time, anywhere, if an emergency pops up, then 145.825 can be used to get a message out.
Now this has nothing to do with P4, Because P4 will have much higher capacity, more bandwith, higher rates, higher frequencies and 24/7 coverage. But the 145.825 channel can still be a small backchannel of support. In fact, we have been encouraging all AMSAT members no matter what their operational preferences, to at least verify their ability to send a single-line-email once every month or so to validate their ability to use this channel. See he web page:
The reason I brought up this topic now, is because of the SUBJECT line of this thread. "One Satellite or Many". And I whole-hartedly support AMSAT's energies toward P4. But the purpose of this message is not towards AMSAT, but to solicit all those universities and non-AMSAT entities that are also building satellites to consider this 145.825 mission.
Beacuse almsot all such LEO satellites need a command system. Most will use AX.25, so why not make your command system double as this emergency message channel in support of 1200 baud messaging? We have had all of these satellites on 145.825, all capable of AX.25 message relay:
and Others in work..
But we have never had more than 2 or at most 3 operational at the same time. If most of these cubesats and university sats that use AX.25 allowed digipeating on 145.825, then we would have a fantastic constellation of nearly continuous coverage of 145.825. Just four such satellites could give us an average acccess wait time of uner an hour. Approaching ten of them could average almost continuous coverage with only 5 minutes or so wait times. A cubest can easily support this mission, since the TX is only one for less than 4% of the time even during normal use.
This is A great Emergency Message Capability that anoyone with a mobile APRS rig could hit from anywhere at any time or without no more than say a 30 minute wait for a pass. We should encourage all those cubesat schools to consider this secondary mission for their TX/RX command system.
Again, not wanting to detract from the P4 dialog, but we should endorse this new P4 Emergency Communications initiative of AMSAT and look for ways to make it a reality. FLying 145.825 digipeaters on everything that files in LEO is one supportive way to add some EmCom back-channel capability while not detracting any energy from P4.
If you haven't sent your emergency email test message, dust off that old TNC and give it a go...
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