Community Survey Request -- crosslinks, multi-hop packet, and satellite DX
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
one clarification point.. all opinions are good, and I'm interested in them.
I meant all opinions, whether positive ('Hey that's cool, I'd play') or negative ('stupid idea, will never work') related to the concept of operations, are welcome.
-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 4:26 PM, 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
Would it/could it/should it use the standard APRS mode on 145.825 MHz with ARISS path to take advantage of the ISS and PSAT digipeaters? That could allow for longer/more robust sat DX opportunities. If it were like the existing digipeaters that use APRS it would be easy for me to use with my Kenwood TH-D72 but if it required specially configured computer software that would be harder for me to use as I only have a portable sat setup now.
73, John Brier KG4AKV
On Sun, Apr 2, 2017 at 4:31 PM, Zach Leffke [email protected] wrote:
one clarification point.. all opinions are good, and I'm interested in them.
I meant all opinions, whether positive ('Hey that's cool, I'd play') or negative ('stupid idea, will never work') related to the concept of operations, are welcome.
-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 4:26 PM, 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
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
still working out details, so I can't give concrete answers. But here is the spirit of the idea to try to answer your question (specifically about packet crosslink comms, not the S-E range measurements):
One decision that has been made is the Astrodev Lithium radio on UHF frequencies (radios have been bought). Single UHF frequency per bird for uplinking and downlinking on (half duplex). A second common/shared UHF freq for the crosslink. FSK9600/AX.25 UI for all up and down links (I'm 99% sure the Lithium can't do AFSK1200, but still investigating, and if anyone on the list has experience with the Lithium I'm all ears). Crosslink radio is the RFM69HCW, which is similar to MO-76's RFM22 radio, also on UHF freqs.
So a definitely frequency incompatibility with existing APRS fleet.
Other than the frequency incompatibility though, when switched into 'weekend ops' mode, it would likely be standard FSK9600 up and down, AX.25 UI Frame, and APRS 'encoded' packets from/to the ground. The crosslink is a more custom link that would be 'transparent' to the operator. It is still FSK9600, but not AX.25 (based on RFM69HCW chips capabilities). The students are currently playing with prototypes to work out the specifics for the crosslink data format. Its easier to use the built in 'packet mode' on the chips, but more flexible (and harder) to use the 'transparent mode.' We're currently examining both options.
So FSK9600/AX.25 UI/APRS encoded up, data decoded and updated per APRS digipeat standards, APRS message encapsulated for transport across the RFM69 crosslink, then APRS message updated again at the next satellite, then downlinked in FSK9600/AX.25 UI/APRS format. The original receiving bird will possibly also digipeat on the Lithium radio as well as sending to the crosslink radio to 'confirm' reception of the uplink, since the crosslink will be different freq, different protocol, still TBD though. so 3 freqs (one up, one across, one down), probably two protocols (one for up/down, one for across).
As far as software/hardware goes on the ground, standard TNCs capable of 9600 baud comms should work, much like the current operating mode for ARISS packet. So D700s/710s for sure should be able to play, as well as any radio with a 9600 baud data jack (and standard AX.25 TNC) should also work. Any APRS software driving the TNC should work as well. My hope is that any 'special software' that might ride on top of that would be available on github for the interested user (likely derived from the open source Fox Dashboard currently out there, but again, undergrad student project here).
For those interested in the S-to-E measurements, with enough G/T, some recommended HW would need to be obtained (according to a 'User Guide,' still to be written, but basically some cheap parts from Adafruit/Sparkfun) and the same Dashboard mentioned above would have the relevant code to use that HW and obtain the data and forward on to our servers.
Hope that helps clarify the CONOP.
-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 4:42 PM, John Brier wrote:
Would it/could it/should it use the standard APRS mode on 145.825 MHz with ARISS path to take advantage of the ISS and PSAT digipeaters? That could allow for longer/more robust sat DX opportunities. If it were like the existing digipeaters that use APRS it would be easy for me to use with my Kenwood TH-D72 but if it required specially configured computer software that would be harder for me to use as I only have a portable sat setup now.
73, John Brier KG4AKV
On Sun, Apr 2, 2017 at 4:31 PM, Zach Leffke [email protected] wrote:
one clarification point.. all opinions are good, and I'm interested in them.
I meant all opinions, whether positive ('Hey that's cool, I'd play') or negative ('stupid idea, will never work') related to the concept of operations, are welcome.
-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 4:26 PM, 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
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
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
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 [email protected] 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.
- 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.
- With your 2-port digi, the repeated packets between satellites will
not be interfered with by multiple up link signals. Improving the success rate.
- 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 [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
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:
- 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 [email protected] 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.
- 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.
- With your 2-port digi, the repeated packets between satellites will
not be interfered with by multiple up link signals. Improving the success rate.
- 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 [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
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!
- 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.
- 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.
- 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.
- 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.
- 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.
- 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:
- 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 [email protected] 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.
- 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.
- With your 2-port digi, the repeated packets between satellites will
not be interfered with by multiple up link signals. Improving the success rate.
- 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 [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
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
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
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
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
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 [email protected] wrote:
- 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
participants (5)
-
Greg D -
John Brier -
KO6TZ Bob -
Stefan Wagener -
Zach Leffke