[amsat-bb] Community Survey Request -- crosslinks, multi-hop packet, and satellite DX
zleffke at vt.edu
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
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.
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
> 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:
>> 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
>> 2) With your 2-port digi, the repeated packets between satellites will
>> not be interfered with by multiple up link signals. Improving the success
>> 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.....
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