[amsat-bb] Community Survey Request -- crosslinks, multi-hop packet, and satellite DX

Greg D ko6th.greg at gmail.com
Mon Apr 3 01:49:25 UTC 2017

Interesting proposal, with 3 universities "competing".  Images of Battle
Bots in Space coming to mind...

Given that UHF is less efficient for distance contacts (at least by the
physics), and that you'll be running the linking radios at a low power
level, what sort of distance between the satellites do you expect to
maintain contact?  I'm presuming that the cubes are not going to be
actively stabilized, and that the antennas will be more-or-less

Which brings up the last thought...  As the satellites spin, their
respective antenna polarizations will rotate with them.  How will the
satellites deal with cross polarization effects (20-ish dB loss)?  Given
a random polarization between any two satellites, plus the 70cm path
loss penalty, the chances of getting through all 3 birds once they
separate could be vanishingly small, no?

Still, we're getting quite a flury of reports recently of FunCube
telemetry via FO-29, so it is certainly possible for this to work. 
Suggestion might be to figure out why FunCube to FO-29 is working, and
make sure that is part of your design.

Good luck!

Greg  KO6TH

Zach Leffke wrote:
> Hello fellow satellite nuts!
> This email is to humbly request the opinions of those in the Amateur
> Satellite Community about the idea of setting new satellite DX
> records.  Nothing formal, you can email on list or off list as you
> think appropriate.
> So here is the idea:  What if there were a constellation of three
> satellites (3 1Us), built by students (undergrads) at three different
> universities, but launched together and deployed from the same
> deployer that had crosslink packet communications built into the
> design.  Then, what if those birds were licensed via the Amateur Radio
> route (instead of Experimental as is the norm for most University
> birds, with some notable exceptions of course) allowing the entire
> global amateur satellite community to use the crosslink capability in
> an attempt to set new satellite DX records?
> Now, there is a primary science mission (pseudo-range determination as
> the constellation separates, different mass and drag profiles for each
> bird) so during the work week, science happens, but on the weekends,
> the constellation is made available to the community for crosslink
> packet comms.  Additionally, if your setup has enough G/T to monitor
> the lower power crosslink comms, and with a little bit of technical
> tweaking to your ground station (you would need GPS based PPS to
> measure propagation time, maybe ~$100 invested), you could participate
> in Space to Earth pseudo-range measurements that would contribute to a
> secondary orbit determination goal.  To be clear, the up and down
> linking for the satellite DX attempts would be standard FSK9600,
> AX.25, so as long as your station can do that, you can use the
> crosslink path for multi-hop comms.  Its only the S-to-E pseudo range
> measurement that would require a bit of additional HW.
> Does this sound interesting?  Would you as an operator be interested
> in multi-hop satellite packet comms?  Do you think this type of
> operating schedule is acceptable (weekends) to justify Amateur Radio
> licensing instead of Experimental?  Would you be interested in
> contributing to the science mission (S-to-E pseudo-range
> measurement)?  Would you track the telemetry downlinks and forward
> that data on to the mission data warehouse?
> Any and all opinions, good or bad, are welcome.  Again, on or off list
> as you see appropriate is fine with me.  My goal with this is to get a
> sense of what the community's opinion on this topic is and if the
> constellation were available for use, how much interest there would be
> in this type of operation.
> Thanks in Advance!
> Sincerely,
> Zach, KJ4QLP

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