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CX2SA > SATDIG 04.04.17 03:52l 845 Lines 34409 Bytes #999 (0) @ WW
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To : SATDIG@WW
Today's Topics:
1. Re: Community Survey Request -- crosslinks, multi-hop packet,
and satellite DX (Zach Leffke)
2. Re: Community Survey Request -- crosslinks, multi-hop packet,
and satellite DX (Zach Leffke)
3. Re: Amsat live Oscar satellite status page (Joe Fitzgerald)
4. Re: Community Survey Request -- crosslinks, multi-hop packet,
and satellite DX (KO6TZ Bob)
5. Re: Community Survey Request -- crosslinks, multi-hop packet,
and satellite DX (Greg D)
6. Working from EK28. (David Maciel (XE3DX))
7. amsat.org.ar online again (Pedro Converso)
8. Re: Community Survey Request -- crosslinks, multi-hop packet,
and satellite DX (Zach Leffke)
9. Re: Community Survey Request -- crosslinks, multi-hop packet,
and satellite DX (John Brier)
10. W5PFG/p DM83/93 line tonight April 3, 2017 (Clayton Coleman)
----------------------------------------------------------------------
Message: 1
Date: Sun, 2 Apr 2017 20:13:06 -0400
From: Zach Leffke <zleffke@xx.xxx>
To: amsat-bb@xxxxx.xxx
Subject: Re: [amsat-bb] Community Survey Request -- crosslinks,
multi-hop packet, and satellite DX
Message-ID: <f2b2f37a-a2f0-09a1-cb5f-fc04ecc38a6e@xx.xxx>
Content-Type: text/plain; charset=windows-1252; format=flowed
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@xxxxxxx.xxx> 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@xxxxx.xxx. 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@xxxxx.xxx. 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
------------------------------
Message: 2
Date: Sun, 2 Apr 2017 20:16:33 -0400
From: Zach Leffke <zleffke@xx.xxx>
To: amsat-bb@xxxxx.xxx
Subject: Re: [amsat-bb] Community Survey Request -- crosslinks,
multi-hop packet, and satellite DX
Message-ID: <a28b8fdb-1897-e050-2764-2397e31bd88e@xx.xxx>
Content-Type: text/plain; charset=windows-1252; format=flowed
Oh and I should also mention that for #1 there, I'm really really
pushing that 'providing a service to the Amateur Radio Community' be an
actual project goal. Like, they can't declare mission success unless
hams are also using the constellation. So 'distance records' per say
aren't a requirement, but if I get my way, 'Providing Amateur Service'
will be on the Mission Goals list along with the science goals.
-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 8:13 PM, Zach Leffke wrote:
> 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@xxxxxxx.xxx>
>> 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@xxxxx.xxx. 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@xxxxx.xxx. 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@xxxxx.xxx. 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
------------------------------
Message: 3
Date: Sun, 2 Apr 2017 20:58:03 -0400
From: Joe Fitzgerald <jfitzgerald@xxxx.xxx.xxx>
To: amsat-bb@xxxxx.xxx
Subject: Re: [amsat-bb] Amsat live Oscar satellite status page
Message-ID: <ffa8876f-d66c-fafc-1939-5b064070a936@xxxx.xxx.xxx>
Content-Type: text/plain; charset=windows-1252
Someone played an April Fools joke on us and slipped in some naughty
stuff through the submission page. I plugged the hole and removed the
offending database entries.
As always, send problem reports to webmaster@xxxxx.xxx for fastest results.
73 de KM1P Joe
------------------------------
Message: 4
Date: Sun, 2 Apr 2017 18:00:26 -0700
From: KO6TZ Bob <my.callsign@xxxxxxx.xxx>
To: amsat-bb@xxxxx.xxx
Subject: Re: [amsat-bb] Community Survey Request -- crosslinks,
multi-hop packet, and satellite DX
Message-ID: <69d41efe-f8cf-4348-06a1-a893af41ccf9@xxxxxxx.xxx>
Content-Type: text/plain; charset=utf-8; format=flowed
Zach,
Thinking about this, when the satellites are still bunched up in the
days soon after launch, everyone would be able to confirm their own 2 or
3 Hop packet. It is only after the satellites spread out that distant
stations will be needed to confirm the multi-hop. Certainly it takes a
DX station for a DX contact.
BOB
KO6TZ
------------------------------
Message: 5
Date: Sun, 2 Apr 2017 18:49:25 -0700
From: Greg D <ko6th.greg@xxxxx.xxx>
To: Zach Leffke <zleffke@xx.xxx>, amsat-bb@xxxxx.xxx
Subject: Re: [amsat-bb] Community Survey Request -- crosslinks,
multi-hop packet, and satellite DX
Message-ID: <9752b837-043f-8a37-ca89-21425b7969f3@xxxxx.xxx>
Content-Type: text/plain; charset=us-ascii
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
omnidirectional.
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
>
>
------------------------------
Message: 6
Date: Sun, 2 Apr 2017 20:59:46 -0500
From: "David Maciel (XE3DX)" <david.xe3dx@xxxxx.xxx>
To: Grupo Amsat BB <amsat-bb@xxxxx.xxx>
Subject: [amsat-bb] Working from EK28.
Message-ID:
<CA+3j0OOE0WwPyOu89fsesZzRX4S5p8wqM50HVsbCethu83C9ZA@xxxx.xxxxx.xxx>
Content-Type: text/plain; charset=UTF-8
Hi guys, I am now in EK28, Coatzacoalcos, Veracruz. I'm going to work on
FM and SSB satellites in my free time, I think they're going to be few
passes, the office work to occupy all day, maybe be here Monday and Tuesday
only. I will be in touch via twitter @ xe3dx, contacts are confirmed via
direct or LoTW preference. I hope to listen to them in the birds and to be
able to give this rare grid on the Gulf of Mexico.
PS.- Please be very patient on the FM satellites, I am getting very noisy
on my Arrow antenna, sometimes I do not hear everyone's calls. You can help
a good QSO by using the "International Phonetic Code".
David Maciel XE3DX
*http://www.qsl.net/xe3dx/ <http://www.qsl.net/xe3dx/>*
*david.xe3dx@xxxxx.xxx <david.xe3dx@xxxxx.xxx>*
------------------------------
Message: 7
Date: Sun, 2 Apr 2017 23:59:45 -0300
From: Pedro Converso <pconver@xxxxx.xxx>
To: AMSAT <amsat-bb@xxxxx.xxx>
Subject: [amsat-bb] amsat.org.ar online again
Message-ID:
<CANTZqKm64yMVG8pva1rt61NpebpnVZw9VB4xyQNXbJ5KkPrayA@xxxx.xxxxx.xxx>
Content-Type: text/plain; charset=UTF-8
Site amsat.org.ar had been recovered and is online again.
Web available at http://amsat.org.ar
Satellite Passes at http://amsat.org.ar/pass
SAm Satellite logs http://lu7aa.org.ar/log.html
Lusex Logs at http://lusex.org.ar
Latest Keplerians http://lu7aa.org.ar/text/keps.txt
WSPR PicoBalloon http://lu7aa.org.ar/wspr.asp
Calculations at http://amsat.org.ar/calcule.html
QSL Factory at http://lu7aa.org.ar/qsl.asp
In Spanish:
ENACOM Ham exams http://amsat.org.ar/examen/examen?p=n
Amsat-LU Balloons http://amsat.org.ar/globo12.htm
Balloon tracking http://lu7aa.org.ar/vor.asp
LUSAT web site http://lusat.org.ar
Local Weather Sats http://amsat.org.ar/wx
South Am. Sat Award http://amsat.org.ar/certsat.html
Users upload area http://amsat.org.ar/index.php
73, LU7AA, Amsat Argentina
http://amsat.org.ar
info at amsat.org.ar
https://facebook.com/Amsat.LU
------------------------------
Message: 8
Date: Mon, 3 Apr 2017 15:23:40 -0400
From: Zach Leffke <zleffke@xx.xxx>
To: Greg D <ko6th.greg@xxxxx.xxx>, amsat-bb@xxxxx.xxx
Subject: Re: [amsat-bb] Community Survey Request -- crosslinks,
multi-hop packet, and satellite DX
Message-ID: <eb3c4dfc-de50-439d-7c7b-d13ed91c660e@xx.xxx>
Content-Type: text/plain; charset=windows-1252; format=flowed
All,
Many thanks for the plethora of responses on and off list. I think the
simple answer that I was looking for is that generally yes there is
interest from the community.
Below is my attempt to answer multiple questions/points from the
numerous (and appreciated!) comments and questions (some overlap):
1. Technically the universities involved are not competing, we are
cooperating (weekly telecons, ICDs, etc. etc.). Not 3 cubesats designed
in a vacuum (hi hi) the magically working together. Three designs that
are done individually by the institutions, but with open lines of
communication between the respective design teams and subsystem teams
(turns out things are cheaper when you buy in bulk too!). That being
said, if you ever eavesdrop on those phone calls, sometimes it might
sound like competition.......but not unexpected, good lesson in teamwork
for the students (and faculty.....).
2. combination of active and passive stabilization is *planned.* I
have yet to get the 'warm and fuzzy' feeling concerning the active
stabilization bounced against the power budget.
3. Concerning expected ranges..........good question, thats a bit what
the experiment is all about. We're hoping for a few tens of kilometers,
100km is probably a stretch (OK so maybe not satellite DX per se). One
path I have the students going down is tradeoffs between crosslink radio
'modes of operation.' The RFM69HCW has power control, baud rate
control, channel filter BW control, and RX gain control (which affects
linearity and Noise Figure). So maybe as things get further and
further, FSK9600 becomes, FSK48000, then FSK2400, then FSK1200. Maybe
that is tied to a bit of power control where before we drop back in baud
rate we have reached peak power output. Likely not an 'automagic'
decision made onboard, likely all three get commanded to the new modes
of operation by ground. We'll see..........which reminds me, the
students owe me link budgets........
3.b Also, as a super-rough back of the envelope, MO-76 links were
closing with Arrow antennas on the ground when the slant range was on
the order of around 800km. Assume ~12 dB of gain from the arrow, and
the loss of 6dB for doubling of slant range. So if we go from an Arrow
to a 0 dBi antenna, we've cut our range by a quarter (two 6dB losses in
the link) so looking at 200km. BUT MO-76 was low bit rate and various
modulation schemes, some of which are very narrow (like CW). So
accounting for increased bandwidth, and polarization
mismatches..........we'll be happy with a few 10s of km.
4. #s 1, 2, and 3(b) are hinging in large part on simulations in AGI's
STK. First step for the undergrads: learn how to use STK. Very complex
program, very easy for garbage in garbage out situations. But we have a
good number of AOE types working on it.
5. Polarization. Looks like crossed dipoles all around at the moment,
shared between command radio and crosslink radio. Definite problem.
Especially when you consider the L/R flip depending on look angle. So
we're playing around with ideas about monopoles, dipoles, crossed
dipoles, maybe one type on one bird, different type on another, etc.
etc. How does that tie into attitude control. What about if we lose
attitude control. What is the balance between command radio
requirements with the ground and crosslink requirements. What about
when the third bird deploys their drag brake and *speeds up* (one of
those cool counter intuitive things about space, drag break slows them
down, they drop altitude, which speeds them up relative to the other
birds). Lots of tradeoffs to consider.
6. Ground networks. Currently a lot of igates are out there monitoring
UHF bands for ISS (since the 2m radio failure and switch to UHF). Would
be superrrrrrrr sweet if those stayed up and running to monitor the hops
for this constellation. However, it is likely going to be a year or
more before the first launch opportunity (we turned down a chance for
this August, way to soon for us). We are still pretty early in the
evolution of this project, so its possible ISS issues could be rectified
(replacement installed), they switch back to 2m, and the UHF igates go
bye bye. So maybe there will be a follow up request in a year or so to
knock the dust off those raspberry pis and RTL-SDRs and stick em back
outside. We'll see.....Fantastic idea....
7. RFM69 is a cool little radio, but there are definitely better
options for crosslink radios. We settled on this one due to the MO-76
flight heritage from the RFM22 family, the availability of interrupt
outputs (6 different programmeable ones) that we could use for the time
of flight measurements, as well as the ease of integration (C++ code and
arduino sketches exist on github). Our first idea (before we settled on
packet) was inspired heavily by the AO-73/FO-29 (and now EO-79)
crosslinks, so we were looking at what could be done with linear
transponders (and more traditional ranging techniques). Also back then
we were considering PSK modulation formats for the digital data we
needed to move around, along with heavy FEC (again AO-73 inspirations),
but in the end we settled on the RFM69 (mainly once we found out 1U per
bird, so the power budget got thrown out the window). For future flight
opportunities though (Assuming the massive success of this one and the
crazy influx of cash that is sure to ensue for follow up missions, hi
hi), we'll definitely throw all the options back on the table, AFSK,
FSK, PSK, linears, etc.
8. There are probably a few more comments/questions I'm forgetting to
address, I apologize for that. But again many thanks to all for the
very positive feedback and great recommendations.
-Zach
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 9:49 PM, Greg D wrote:
> 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
> omnidirectional.
>
> 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
>>
>>
------------------------------
Message: 9
Date: Mon, 3 Apr 2017 15:32:18 -0400
From: John Brier <johnbrier@xxxxx.xxx>
To: Zach Leffke <zleffke@xx.xxx>
Cc: AMSAT BB <amsat-bb@xxxxx.xxx>
Subject: Re: [amsat-bb] Community Survey Request -- crosslinks,
multi-hop packet, and satellite DX
Message-ID:
<CALn0fKOVTSnC2zDF8V-L7xP5sV-ecJtZ70Bo7_RfGY1CCnhxCw@xxxx.xxxxx.xxx>
Content-Type: text/plain; charset=UTF-8
Regarding 6, the VHF Ericsson is expected to be swapped back in by the
middle of April:
https://twitter.com/RF2Space/status/847840747562835968
On Mon, Apr 3, 2017 at 3:23 PM, Zach Leffke <zleffke@xx.xxx> wrote:
> 6. Ground networks. Currently a lot of igates are out there monitoring UHF
> bands for ISS (since the 2m radio failure and switch to UHF). Would be
> superrrrrrrr sweet if those stayed up and running to monitor the hops for
> this constellation. However, it is likely going to be a year or more before
> the first launch opportunity (we turned down a chance for this August, way
> to soon for us). We are still pretty early in the evolution of this
> project, so its possible ISS issues could be rectified (replacement
> installed), they switch back to 2m, and the UHF igates go bye bye. So maybe
> there will be a follow up request in a year or so to knock the dust off
> those raspberry pis and RTL-SDRs and stick em back outside. We'll
> see.....Fantastic idea....
73, John Brier KG4AKV
------------------------------
Message: 10
Date: Mon, 3 Apr 2017 20:44:09 -0500
From: Clayton Coleman <kayakfishtx@xxxxx.xxx>
To: AMSAT-BB <amsat-bb@xxxxx.xxx>
Subject: [amsat-bb] W5PFG/p DM83/93 line tonight April 3, 2017
Message-ID:
<CAPovOwe8ZqqEZUOBMiG9yOv5Vf7D0AJ3xZaZOsnG2wO4yFCGag@xxxx.xxxxx.xxx>
Content-Type: text/plain; charset=UTF-8
I'll work the following passes tonight from the DM83/93 line in West Texas:
0243 AO-73
0253 EO-88
0319 SO-50
All times UTC.
73
Clayton
W5PFG
------------------------------
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End of AMSAT-BB Digest, Vol 12, Issue 89
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