[amsat-bb] APRS Cubesat LEO constellation

Robert Bruninga bruninga at usna.edu
Wed Apr 22 14:14:17 PDT 2009

> Will there be any other electronics onboard 
> these cubesats, or just the MT-TT4? 
> http://www.byonics.com/microtrak/mt-tt4.php

Our particular cubesat will also have a basic stamp pic
processor to do the attitude control to keep it pointed at the
sun.  But it is not needed for any other function.  All of our
satellites to date flew with no other CPU or processor on board,
other than the TNC itself.  Just like this MT-TT4, the KPC3
TNC's we flew before in both PCSATS, ANDE and RAFT have all the
functions you need.  Comms, command, inputs, outputs, telemetry,
beacons, digipeater etc.

And even without attitude control a four petal design like we
have as long as there are solar panels on all surfaces and the
petals go back 45 degrees, will have at least half the power as
if it was sun pointing.

Of course we have a 555 timer chip to reset the TNC if it gets
locked up.


> On Wed, Apr 22, 2009 at 1:16 PM, Robert Bruninga 
> <bruninga at usna.edu> wrote:
> 	> A last comment, a LEO would be virtually worthless
> 	> for Emergency NET communications and HF is still
> 	> a viable and reliable means of communications...
> 	Well, I still think a bunch of 145.825 APRS digipeating
> 	satellites in LEO that would allow text-messaging from
> 	in the world at any time, downlinked into the
> 	system and hence global internet connectivity is still a
> 	way to go for basic messaging for emergency response.
With just
> 	6 such tiny 4" cubesats, you could get a message
in-or-out with
> 	no more than a half hour wait from the front panel of
your APRS
> 	mobile radio.  With a dozen of these, you could have
> 	communications anywhere instantly or with no more than a
> 	minute wait.
> 	Our goal is to get more of these up there to join the
> 	digipeater, but of the 4 we have lanuched so far, all
> 	short-term orbits and so the most we have ever had
> 	at one time was 3 (PCSAT-1, ANDE and RAFT).  That is one
of the
> 	main reasons we wanted to see ISS on 145.825 to join the
> 	constellation.  ISS was still on 145.800 during most of
the life
> 	of those three birds (which were all on 145.825)
> 	Today, with 6 AA NiCd's, a 19" whip antennna, and a 3.4"
> 	APRS Microtacker TNC/Radio you can throw together an
> 	satellite for under $400.  Add cheap solar panels, a lot
> 	sweat equity and then find a school to provide the
> 	launch, and bingo, A LEO satellite with great utility
> 	anyone can use while mobile for text messsaging and
email from
> 	the front panel of their APRS radio.
> 	Please see the Microtrack TNC/Radio which can serve as
> 	entire Comms, Command, Control and Telemetry module:
> 	http://www.byonics.com/microtrak/mt-tt4.php
> 	And see our cubesat project:
> 	though this web page needs to be significanly updated..
> 	Bob, WB4APR
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> Andrew Koenig

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