FUNCube-1 (AO-73) Telemetry via FO-29??
While monitoring FO-29 for activity tonight, I saw what appeared to be the distinctive waveform of the telemetry stream from FUNCube-1.
Is this common? Or even possible? It was certainly a first for me. I see that the telemetry frequency on FUNCube-1 falls inside of the uplink range for FO-29.
The signal was a little too weak for me to decode with the FUNCube dashboard ground station app, but I made some screen shots if anyone is interested. My Tweet with pics is at:
https://twitter.com/scott23192/status/763990419378057216
FUNCube-1 was over Alaska & FO-29 was flying North-to-South down the Eastern US. Would that put them in sight of each other?
If this is what happened, then it's my first satellite-to-satellite reception, which I thought was pretty cool.
Thanks!
-Scott, K4KDR Montpelier, VA USA
El 12/08/16 a las 08:58, Scott escribió:
While monitoring FO-29 for activity tonight, I saw what appeared to be the distinctive waveform of the telemetry stream from FUNCube-1.
Is this common? Or even possible? It was certainly a first for me. I see that the telemetry frequency on FUNCube-1 falls inside of the uplink range for FO-29.
Hi Scott,
Certainly it's FUNCube-1 via FO-29. That's not so common, but I've seen a few reports of this before on the mailing list. Someone even managed to decode the telemetry. Probably you can google if you're interested in previous reports. Also, satellite-to-satellite QSO is also possible for some pairs of satellites and has being done (for AO-7 and FO-29 as far as I can remember). Note that the transponder of FO-29 is quite wide and will retransmit a lot of birds that downlink on 2m, so lots of possibilities for reception via FO-29.
73,
Dani.
It is possible to decode, though conditions need to be just so. I was able to turn this exact phenomenon into a student project at VT for the undergrad SatCom course. The students had to simulate the event to predict when the chain (crosslink) events would occur (line of sight between the two birds and FO-29 over the VTGS), what the Link Budget looks like during the chain event (so we can predict the best opportunity for successful decodes), and what the Doppler profile would look like during the event (which tends to be really different than expected, like the center frequency drifting UP due to the relative motion between the birds). We then used the VTGS to monitor a few of the events based of the student generated schedules and two of the students got extra credit on the project because they were present during a successful demodulation (and their predictions were spot on!).
I posted a short blurb on our facebook page about it: https://www.facebook.com/vtgroundstation/
During that event we were able to dig out 6 packets using GNU Radio and a custom AO-73 modem (Basicaly Phil Karn's AO-40 reference code wraped for GNU Radio, also implemented by a student). Probably of more interest to this list though is Paul's (N8HM) success with standard equipment. He dug out 9 packets using the Funcube Dashboard and I believe the Funcube dongle.
During that particular conjunction event, one REALLY interesting thing that happened is that we caught the instant in time when AO-73 moved out of eclipse. We could see the signal drifting along just a few dB above the noise (willing it to increase just a bit to achieve sufficient SNR for a solid decode) then all of a sudden it jumped up by 10 dB and packets started decoding!
Very cool stuff. FO-29 is one of my favorite birds for looking at these types of exotic cases precisely because it's transponder covers half of the Amateur Satellite Service 2m band. As previously mentioned, lots of opportunities for interesting events (crosslinks, gelocating the FM interferers, etc.). AO-73 is also a great bird because of the Forward Error Correction on the TLM link (among other reasons). For our GNU-Radio modem, we need about 7 dB SNR (including implementation loss there) for solid demodulation.
Fine Business!
-Zach, KJ4QLP
Research Associate Ted & Karyn Hume Center for National Security & Technology Virginia Polytechnic Institute & State University Work Phone: 540-231-4174 Cell Phone: 540-808-6305
On 8/12/2016 4:16 AM, Daniel Estévez wrote:
El 12/08/16 a las 08:58, Scott escribió:
While monitoring FO-29 for activity tonight, I saw what appeared to be the distinctive waveform of the telemetry stream from FUNCube-1.
Is this common? Or even possible? It was certainly a first for me. I see that the telemetry frequency on FUNCube-1 falls inside of the uplink range for FO-29.
Hi Scott,
Certainly it's FUNCube-1 via FO-29. That's not so common, but I've seen a few reports of this before on the mailing list. Someone even managed to decode the telemetry. Probably you can google if you're interested in previous reports. Also, satellite-to-satellite QSO is also possible for some pairs of satellites and has being done (for AO-7 and FO-29 as far as I can remember). Note that the transponder of FO-29 is quite wide and will retransmit a lot of birds that downlink on 2m, so lots of possibilities for reception via FO-29.
73,
Dani.
Sent via [email protected]. 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
El 12/08/16 a las 16:48, Zach Leffke escribió:
For our GNU-Radio modem, we need about 7 dB SNR (including implementation loss there) for solid demodulation.
Hi Zach,
Is this GNU-radio AO-73 receiver available online? It would be interesting to take a look at. How does it compare (in terms of SNR performance) to the dashboard software?
73,
Dani EA4GPZ.
Hi Dani,
Great questions. On my long list of 'TO DOs' for the VTGS is to get our github account up and running to push our satellite GNU Radio work back out to the Open Source community. Once we do I'll post the code along with the pyBOMBS recipes for installation. I don't have an ETA for that though (maybe this Fall semester.....?). There are a few other things in the Out of Tree Module that would be of use to Hams as well. For example we have scramblers and descramblers that are AX.25 compliant. We also have an AFSK TRANSMITTER as well as an AFSK receiver (I've seen a few AFSK/AX.25 GNU Radio projects, but they are all receivers and they don't separate the demodulator from the link layer protocol). Fair warning if I ever do get the code posted and you play with it, the output of the modem is the raw 256 byte packet (after FEC decode and CRC check, that I send to a PDU socket). There is no pretty dashboard in our code. The intent was to develop a separate dashboard for AO-73 that would connect to the GNU-Radio modem over the socket (we operate our ground station remotely from a mini Mission Control at Space@VT). That is also on the long list of to dos.
I've never compared our receiver to the funcube dashboard side-by-side in a real detailed way. That is definitely something I would be interested in seeing the results of. I do use a funcube dongle with the dashboard for student demos with an arrow antenna. I would say comparing my 'impressions' of both is that they both work very well and basically just after AO-73 pops over the horizon we get solid decodes on both (FEC is great!). My gut is that with all of the great folks at AMSAT-UK and all of the good engineering effort they put into that software, that theirs probably performs a bit better. We make up for our probably higher implementation loss by have a pair of 14 element crossed yagis (2 M2 antennas 2MCP14s combined in phase), so lots of gain. The AO-73 dashboard also does the Automatic Frequency Correction, which is something we don't quite have implemented in our GNU Radio flowgraphs yet (we tune either manually or via a Gpredict interface to GNU-Radio to get inside the capture bandwidth of our differential bpsk demod).
Something that would make a good comparison easier to implement, and that I would like to see, is a Linux version (and open source) of the FunCube Dashboard. I don't really want to mess around with Windows emulators on our Linux servers/workstations in the VTGS. That could be a fun student project to try to integrate a Linux version of the Dashboard with the Socket interface to GNU Radio (and would allow us to forward the tlm packets to the data warehouse easier). That's one of the things I really like about the AO-85 dashboard is the cross-platform support.
Good questions, thanks for the interest. I'll try to put more effort into elevating the github thing on the to do list this semester.
-Zach, KJ4QLP
Research Associate Ted & Karyn Hume Center for National Security & Technology Virginia Polytechnic Institute & State University Work Phone: 540-231-4174 Cell Phone: 540-808-6305
On 8/12/2016 10:55 AM, Daniel Estévez wrote:
El 12/08/16 a las 16:48, Zach Leffke escribió:
For our GNU-Radio modem, we need about 7 dB SNR (including implementation loss there) for solid demodulation.
Hi Zach,
Is this GNU-radio AO-73 receiver available online? It would be interesting to take a look at. How does it compare (in terms of SNR performance) to the dashboard software?
73,
Dani EA4GPZ.
Sent via [email protected]. 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
El 12/08/16 a las 17:29, Zach Leffke escribió:
Hi Dani,
Great questions. On my long list of 'TO DOs' for the VTGS is to getour github account up and running to push our satellite GNU Radio work back out to the Open Source community. Once we do I'll post the code along with the pyBOMBS recipes for installation. I don't have an ETA for that though (maybe this Fall semester.....?). There are a few other things in the Out of Tree Module that would be of use to Hams as well. For example we have scramblers and descramblers that are AX.25 compliant. We also have an AFSK TRANSMITTER as well as an AFSK receiver (I've seen a few AFSK/AX.25 GNU Radio projects, but they are all receivers and they don't separate the demodulator from the link layer protocol).
Hi Zack,
Looking forward to it, as this will be useful for me and probably other hams. I understand that it is a bit of work to clean the code up to push to github.
In fact, I also have my own AFSK/AX.25 GNUradio transceiver in github, as I wasn't too happy with any of the other projects (it also does FSK and BSPK, which is useful for QB50p). For AX.25 (de)scrambling I use the default GNUradio blocks. They can be used if you understand what parameters you need to put.
In case anyone is interested:
https://github.com/daniestevez/gr-kiss
http://destevez.net/2016/05/scramblers-and-their-implementation-in-gnuradio/
The AO-73 dashboard also does the Automatic Frequency Correction, which is something we don't quite have implemented in our GNU Radio flowgraphs yet (we tune either manually or via a Gpredict interface to GNU-Radio to get inside the capture bandwidth of our differential bpsk demod).
It's not as good as the software in the dashboard, which will search for the signal in all the passband and track it, but in GNUradio you can use FLL band edge, which will correct mistunings of up to a 1 or 2kHz. Together with Gpredict, this usually solves all tuning problems. Probably you already knew this.
Something that would make a good comparison easier to implement, and that I would like to see, is a Linux version (and open source) of the FunCube Dashboard.
That's one of the things I really like about the AO-85 dashboard is the cross-platform support.
Same opinion here. For me it's a hassle to run the dashboard inside a virtual machine, if only because I have to feed it the audio via wav files. Between linux programs I can use pulseaudio to exchange real time audio.
73,
Dani EA4GPZ.
Hi Zach,
Yes, I got 9 packets using an Arrow, a FT-817ND, and a High Sierra Microwave LNAA432 preamp. I did not decode them live, I was using an Olympus VN-702PC recorder and fed the audio into the Dashboard later. I was not expecting success, but it did work quite well!
73,
Paul, N8HM
On Fri, Aug 12, 2016 at 10:48 AM, Zach Leffke [email protected] wrote:
It is possible to decode, though conditions need to be just so. I was able to turn this exact phenomenon into a student project at VT for the undergrad SatCom course. The students had to simulate the event to predict when the chain (crosslink) events would occur (line of sight between the two birds and FO-29 over the VTGS), what the Link Budget looks like during the chain event (so we can predict the best opportunity for successful decodes), and what the Doppler profile would look like during the event (which tends to be really different than expected, like the center frequency drifting UP due to the relative motion between the birds). We then used the VTGS to monitor a few of the events based of the student generated schedules and two of the students got extra credit on the project because they were present during a successful demodulation (and their predictions were spot on!).
I posted a short blurb on our facebook page about it: https://www.facebook.com/vtgroundstation/
During that event we were able to dig out 6 packets using GNU Radio and a custom AO-73 modem (Basicaly Phil Karn's AO-40 reference code wraped for GNU Radio, also implemented by a student). Probably of more interest to this list though is Paul's (N8HM) success with standard equipment. He dug out 9 packets using the Funcube Dashboard and I believe the Funcube dongle.
During that particular conjunction event, one REALLY interesting thing that happened is that we caught the instant in time when AO-73 moved out of eclipse. We could see the signal drifting along just a few dB above the noise (willing it to increase just a bit to achieve sufficient SNR for a solid decode) then all of a sudden it jumped up by 10 dB and packets started decoding!
Very cool stuff. FO-29 is one of my favorite birds for looking at these types of exotic cases precisely because it's transponder covers half of the Amateur Satellite Service 2m band. As previously mentioned, lots of opportunities for interesting events (crosslinks, gelocating the FM interferers, etc.). AO-73 is also a great bird because of the Forward Error Correction on the TLM link (among other reasons). For our GNU-Radio modem, we need about 7 dB SNR (including implementation loss there) for solid demodulation.
Fine Business!
-Zach, KJ4QLP
Research Associate Ted & Karyn Hume Center for National Security & Technology Virginia Polytechnic Institute & State University Work Phone: 540-231-4174 Cell Phone: 540-808-6305
On 8/12/2016 4:16 AM, Daniel Estévez wrote:
El 12/08/16 a las 08:58, Scott escribió:
While monitoring FO-29 for activity tonight, I saw what appeared to be the distinctive waveform of the telemetry stream from FUNCube-1.
Is this common? Or even possible? It was certainly a first for me. I see that the telemetry frequency on FUNCube-1 falls inside of the uplink range for FO-29.
Hi Scott,
Certainly it's FUNCube-1 via FO-29. That's not so common, but I've seen a few reports of this before on the mailing list. Someone even managed to decode the telemetry. Probably you can google if you're interested in previous reports. Also, satellite-to-satellite QSO is also possible for some pairs of satellites and has being done (for AO-7 and FO-29 as far as I can remember). Note that the transponder of FO-29 is quite wide and will retransmit a lot of birds that downlink on 2m, so lots of possibilities for reception via FO-29.
73,
Dani.
Sent via [email protected]. 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 [email protected]. 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
participants (5)
-
Dani EA4GPZ -
Daniel Estévez
-
Paul Stoetzer -
Scott -
Zach Leffke