[amsat-bb] Re: Double leo satellites

Bob Bruninga bruninga at usna.edu
Sun Sep 14 05:54:55 PDT 2008

> Should it be possible to launch two Leo 
> satellites...(satellite A) retransmitts 
> what it hears to the other Leo satellite
> (Satellite B)... I think in that way i 
> could work NA every day?

That is the intent of the APRS constellation of satellites.  All operating packet on 145.825.  We want to get as many of these satellties in orbit as we can to not only provide continuity of coveratge, but also dual-hop capabilities as you suggest.

APRS can inherently, auomatically, work via dual hops, since it uses a generic path which does not need to be configured for each satellite callsign.

That is also why the ISS moved to 145.825 a year or so ago, to be on the same channel, with PCSAT-1,PCSAT2,ANDE, RAFT, and others.  There have been several instances of dual hop packets.  The longest one recorded was from Africa over the Atlantic to Maryland.  See:

Unfortunately, only ISS and PCSAT-1 remain in orbit and PCSAT-1 only works under some conditions, and ISS only works under others.  But if you can find them both working at the same time, then dual hops are possible.

You can watch the downlinks from these two birds and look for activity and dual hops just by looking through the on-line real-time downlink logs:

www.ariss.net for the ISS
http://pcsat.aprs.org for the others

You can see that ISS has been off the air for 79 days except for a brief period 2 weeks ago.  And PCSAT-1 (W3ADO-1) continues to limp along with some lucky packets during northern hemisphere mid-day passes.

Ideally, if we can get 6 to 10 small APRS satellites on 145.825, we can provide near continuous message/email/status capabiliy from anywhere on Earth at any time.  That is why I encourage all Universities making CUBESATS or other small satellites to include a 145.825 1200 baud packet link so their satellites can be used in this constellation after their primary mission is over..

Our next Satellite from the Naval Academy will actually be two-cubesats-at-once.  Both on 145.825 with APRS transponders.

Please, if anyone is working with other universities, see if they would consider this global constellation mission for their transponder...

Bob, Wb4APR

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