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

Mon Apr 3 00:13:06 UTC 2017

Thanks again for the responses both on and off list, keep 'em coming!

1.  No, not really a an academic goal.  But cross linking is a 
requirement.  And pseudo-range determination is a requirement. So, 
'distance records' or at least multi-hop comms are a natural extension.

2.  3 1Us in a single P-POD.  But, different drag profiles and different 
masses.  One has a drag brake that will be deployed shortly after 
deployment from the PPOD and after initial checkout.  The other two have 
the same profile but different masses.

3.  Aiming for an ISS deployment.  Overall science goal is to generate 
data for atmospheric density models at LEO and low LEO altitudes. So 
higher would be better for the crosslinking/distance, but would be worse 
for the science.  So it will be a relatively short mission, current 
estimates on the order of 6 months or so.

4.  We're still sorting out the exact operating details. Earlier I gave 
a two satellite example, simplest case.  We'll see how complicated we 
can make it as we move forward.  One options is up to one, across to the 
other two, and down from both.  Another is the triple hop (the really 
desirable one), where each time it hits a new bird, it gets sent on the 
crosslink and on the downlink.  We don't have a specific plan yet, which 
is part of why I sent out the survey request, to see what people would 
be interested in, if at all, so we can try to incorporate it into the 
design.

5.  yesss!!! different modes, different options, different ways to 
reconfigure, either from the ground or with built in 'fallback' 
operating modes.  All the kind of things we're discussing and working 
through, but are leaving to the students to decide / figure out.  I'm 
only a faculty advisor on the project, so can lob recommendations at my 
team, but I'm not in charge.  We know for a fact (or are at least really 
really sure) that we will almost certainly lose one of them (the one 
with the drag brake) faster than the others.  So the comms will need to 
be able to adapt.

6.  Thats all the money we could drum up for the mission.  But we'll 
take it, and are grateful for the chance here!  I'm just hoping we can 
balance power budgets appropriately, cause yeah, its tight.

-Zach, KJ4QLP

Research Associate
Aerospace Systems Lab
Ted & Karyn Hume Center for National Security & Technology
Virginia Polytechnic Institute & State University
Work Phone: 540-231-4174
Cell Phone: 540-808-6305

On 4/2/2017 7:12 PM, Stefan Wagener wrote:
> A few quick thoughts:
>
> 1. Is the "long distance record" truly an academic goal? I hope that this
> is just a side effect of a more scientific endeavour :-)
> 2. How will the deployment of the satellites being scheduled? Too close
> together means long time for separation to make it useful but longer
> lifetime for use. Too much initially separation and the satellites won't
> see each other for too long.
> 3. How about the deployment altitude. The higher the better?
> 4. What happens to the sat in the middle, just a link between the other
> ones and no direct contact/use?
> 5. How can the system be programmed that if one satellites fails it still
> works?
> 6. Why 1Us and not bigger for better power budget and redundancies?
>
> Have fun,
>
> 73, Stefan VE4NSA
>
> On Sun, Apr 2, 2017 at 5:54 PM, KO6TZ Bob <my.callsign at verizon.net> wrote:
>
>> Zach,
>>
>> I like what I see so far on your initial proposal.
>>
>> In the past, I have been involved with 2-HOP and 3-HOP packet attempts
>> using various combinations of the ISS, NO-44 and NO-84 when they were all
>> working on 145.825MHz.
>>
>> Your proposal of using a 9K6 FSK 2-port_digi's on board three satellites
>> in the same orbital track resolves what I believe to be the main challenges
>> we faced in our 1200 baud experiment.  If the footprints overlap, the
>> satellites should be able to talk to each other.
>>
>> 1)  Since the satellites were in different orbits, there was Doppler shift
>> in the signal between them.  In your proposal, doppler is minimal for FM
>> packet.
>>
>> 2)  With your 2-port digi, the repeated packets between satellites will
>> not be interfered with by multiple up link signals. Improving the success
>> rate.
>>
>> 3)  I find that 9K6_FSK is as easy to copy as 1200baud, so efficiency in
>> channel usage is gained.
>>
>> Once the operators acquire confidence in establishing basic 2 & 3 Hop
>> packet contacts, the other experiments and distance records you mentioned
>> will follow.
>>
>> I'm in.....
>>
>> BOB
>> KO6TZ
>>
>> _______________________________________________
>> Sent via AMSAT-BB at amsat.org. AMSAT-NA makes this open forum available
>> to all interested persons worldwide without requiring membership. Opinions
>> expressed
>> are solely those of the author, and do not reflect the official views of
>> AMSAT-NA.
>> Not an AMSAT-NA member? Join now to support the amateur satellite program!
>> Subscription settings: http://www.amsat.org/mailman/listinfo/amsat-bb
>>
> _______________________________________________
> Sent via AMSAT-BB at amsat.org. AMSAT-NA makes this open forum available
> to all interested persons worldwide without requiring membership. Opinions expressed
> are solely those of the author, and do not reflect the official views of AMSAT-NA.
> Not an AMSAT-NA member? Join now to support the amateur satellite program!
> Subscription settings: http://www.amsat.org/mailman/listinfo/amsat-bb