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Radio Amateur Copies Signal from Mars-Orbiting Satellite

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Re: Radio Amateur Copies Signal from Mars-Orbiting Satellite

#31

Post by lebuffon »

treesknees wrote: post #29

As someone not familiar with ham - what can you do with this signal? Can you decode it to view stats or pictures? Or is it mostly just "hearing" it speak to Earth? I'm also curious what prevents say an amateur operator or even another country from sending commands or disrupting communication to remote systems on Mars. Is it the just the amount of work they'd have to do, proprietary/secret protocol, encryption?

The amateur radio frequencies that are "legal" for a ham operator to transmit on are well defined. If the NASA devices used Amateur frequencies for commercial work I believe they would be breaking US law as well. So the terms of the amateur license prohibit transmitting signals to the remote systems on Mars.

The practical requirements of getting a strong enough signal to Mars would require a big dish to focus the energy and some high power microwave equipment which make it more difficult but not impossible given enough resources. Then as you mentioned one needs to know the communication protocols.

BTW there were Ham built satellites in orbit, that piggybacked onto other missions. (OSCAR) Not sure if they are still in orbit. And again they used reserved spectrum for licensed experimental Amateur radio stations.

Re: Radio Amateur Copies Signal from Mars-Orbiting Satellite

#32

Post by madengr »

myth2018 wrote: post #13
schoen wrote: post #9

Earlier quoted context omitted.

Apparently the Deep Space Network dishes are (now up to) 34 meters: https://www.nasa.gov/feature/jpl/nasa-s-deep-space-network-w... I guess they achieve higher reliability than amateurs on a number of counts, but that contrast also makes the amateur efforts seem even more impressive. (Since area is proportional to the square of diameter, the DSN dishes would each be over 3,000 times larger than Scott Tilley's dish.)

Indeed, but there are other important factors besides size. DSN have way bigger requirements in terms of signal to noise ratios, since they need to demodulate received signals. Scott Tilley, on the other hand, seems to be mainly interested on detecting the presence of signals, not necessarily extracting information from it. Then, he could build a bigger dish, but he doesn't actually need one to achieve his goal. I no…

I'm the shadow banned commenter, due to comments that fall in the right half of the plane; disagreeable to HN mods.

But not to digress, it's likely 120 degree BPSK (i.e. QPSK with a DC level for the Q). I'm not in the deep space field (but do RF/Microwave professionally), but the DSN (deep space network) on Earth sends out a carrier with 120 BPSK modulation with PN (pseudo noise) code. The spacecraft transverts and sends that back (a bent pipe). Velocity is determined via Doppler shift of the carrier. Range from the delay in the PN code. So knowing velocity and range (and bearing using antenna pointing or interferometry), you can track the spacecraft with great precision.

Even without a bent pipe, you need carrier recovery first, before you can demodulate, and the leakage helps with that. You can also do geolocation with carrier leakage (e.g. ARGOS satellites) and via isodops (contours of constant Doppler shift) like a reverse GPS uses isochrones (contours of constant time delay).

So in short, there are benefits of wasting carrier energy. The ham guy can detect it as he can do lots and lots of coherent averaging (i.e. long FFTs or very narrow resolution bandwidths) to find that carrier. Though to recover any modulation will take a much bigger (or lower noise temp) antenna.

Re: Radio Amateur Copies Signal from Mars-Orbiting Satellite

#33

Post by weezer »

lebuffon wrote: post #31
treesknees wrote: post #29

As someone not familiar with ham - what can you do with this signal? Can you decode it to view stats or pictures? Or is it mostly just "hearing" it speak to Earth? I'm also curious what prevents say an amateur operator or even another country from sending commands or disrupting communication to remote systems on Mars. Is it the just the amount of work they'd have to do, proprietary/secret protocol, encryption?

The amateur radio frequencies that are "legal" for a ham operator to transmit on are well defined. If the NASA devices used Amateur frequencies for commercial work I believe they would be breaking US law as well. So the terms of the amateur license prohibit transmitting signals to the remote systems on Mars. The practical requirements of getting a strong enough signal to Mars would require a big dish to focus the ene…

What you said is mostly true but there are also frequencies that ham operators can transmit in, but only have secondary priority to other uses.

For example hams can only transmit in the 1.25 meter band if they don't interfere with other users like the Automated Maritime Telecommunications Systems (AMTS).

https://hamradioprepper.com/us-amateur-radio-bands/

Re: Radio Amateur Copies Signal from Mars-Orbiting Satellite

#34

Post by [deleted] »

madengr wrote: post #32
myth2018 wrote: post #13

Earlier quoted context omitted.

Indeed, but there are other important factors besides size. DSN have way bigger requirements in terms of signal to noise ratios, since they need to demodulate received signals. Scott Tilley, on the other hand, seems to be mainly interested on detecting the presence of signals, not necessarily extracting information from it. Then, he could build a bigger dish, but he doesn't actually need one to achieve his goal. I no…

I'm the shadow banned commenter, due to comments that fall in the right half of the plane; disagreeable to HN mods. But not to digress, it's likely 120 degree BPSK (i.e. QPSK with a DC level for the Q). I'm not in the deep space field (but do RF/Microwave professionally), but the DSN (deep space network) on Earth sends out a carrier with 120 BPSK modulation with PN (pseudo noise) code. The spacecraft transverts and s…

[deleted]

Re: Radio Amateur Copies Signal from Mars-Orbiting Satellite

#35

Post by myth2018 »

treesknees wrote: post #29

As someone not familiar with ham - what can you do with this signal? Can you decode it to view stats or pictures? Or is it mostly just "hearing" it speak to Earth? I'm also curious what prevents say an amateur operator or even another country from sending commands or disrupting communication to remote systems on Mars. Is it the just the amount of work they'd have to do, proprietary/secret protocol, encryption?

My two cents in addition to lebuffon's reply:

The occasional amateur gear is usually not enough to demodulate signals from Mars, since they're too faint. You'd need much larger dishes to, roughly speaking, "ingest" more energy into your receiver so that it become more distinguishable from noise and you can extract information from it.

It would be possible to demodulate with smaller, amateur dishes if the spacecraft transmitted in a very narrow bandwidth. It wouldn't make sense for space agencies to do that, though, since they would trade higher bit rates for cheaper receivers, whilst powerful receivers aren't that difficult to build and are totally on budget for an agency capable of launching a spacecraft.

But I must say that that would be a very nice citizen science project.

Re: Radio Amateur Copies Signal from Mars-Orbiting Satellite

#36

Post by tyldum »

myth2018 wrote: post #13
schoen wrote: post #9

Earlier quoted context omitted.

Apparently the Deep Space Network dishes are (now up to) 34 meters: https://www.nasa.gov/feature/jpl/nasa-s-deep-space-network-w... I guess they achieve higher reliability than amateurs on a number of counts, but that contrast also makes the amateur efforts seem even more impressive. (Since area is proportional to the square of diameter, the DSN dishes would each be over 3,000 times larger than Scott Tilley's dish.)

Indeed, but there are other important factors besides size. DSN have way bigger requirements in terms of signal to noise ratios, since they need to demodulate received signals. Scott Tilley, on the other hand, seems to be mainly interested on detecting the presence of signals, not necessarily extracting information from it. Then, he could build a bigger dish, but he doesn't actually need one to achieve his goal. I no…

And smaller dish has larger beam width, making it really difficult to track the signal.

Re: Radio Amateur Copies Signal from Mars-Orbiting Satellite

#37

Post by myth2018 »

chokeartist wrote: post #30
myth2018 wrote: post #13

Earlier quoted context omitted.

Indeed, but there are other important factors besides size. DSN have way bigger requirements in terms of signal to noise ratios, since they need to demodulate received signals. Scott Tilley, on the other hand, seems to be mainly interested on detecting the presence of signals, not necessarily extracting information from it. Then, he could build a bigger dish, but he doesn't actually need one to achieve his goal. I no…

> I've always asked myself why spacecrafts "wasted" energy with carriers and never realized they make the signal easer to find. Not exactly. You need a carrier wave / signal to modulate information onto. Can't modulate info onto nothing.

Yes, you can. There are a number of supressed-carrier modes, e.g. single side band.

Re: Radio Amateur Copies Signal from Mars-Orbiting Satellite

#38

Post by myth2018 »

madengr wrote: post #32
myth2018 wrote: post #13

Earlier quoted context omitted.

Indeed, but there are other important factors besides size. DSN have way bigger requirements in terms of signal to noise ratios, since they need to demodulate received signals. Scott Tilley, on the other hand, seems to be mainly interested on detecting the presence of signals, not necessarily extracting information from it. Then, he could build a bigger dish, but he doesn't actually need one to achieve his goal. I no…

I'm the shadow banned commenter, due to comments that fall in the right half of the plane; disagreeable to HN mods. But not to digress, it's likely 120 degree BPSK (i.e. QPSK with a DC level for the Q). I'm not in the deep space field (but do RF/Microwave professionally), but the DSN (deep space network) on Earth sends out a carrier with 120 BPSK modulation with PN (pseudo noise) code. The spacecraft transverts and s…

Thank you so much for the information.

In case you have any links to share about how DSN works, I'd appreciate.

And thank you also for mentioning coherent averaging. I'm more or less familiar with the concept but I've been trying to find out the name of the thing so that I could google on how to implement it (I've been collecting some information for assessing the feasibility of a project involving high-loss antennas).

Besides, I've never wondered how they tracked spacecrafts, especially those ones as far as new horizons and voyagers.

Re: Radio Amateur Copies Signal from Mars-Orbiting Satellite

#39

Post by texasbigdata »

DrAwdeOccarim wrote: post #25
texasbigdata wrote: post #21

Earlier quoted context omitted.

As an outsider what’s the order of magnitude on humans that have this setup currently functional? 100? 1,000? Etc.

There are 774,562 amateur radio licensed people in the US [1]. I would assume 10% of them are super active, so 77,456, and of those super active people, I'd say 1% of them are pushing the boundaries. So 1000? [1] http://www.arrl.org/fcc-license-counts

This comment is amazing. Thank you so much.

Re: Radio Amateur Copies Signal from Mars-Orbiting Satellite

#40

Post by madengr »

myth2018 wrote: post #38
madengr wrote: post #32

Earlier quoted context omitted.

I'm the shadow banned commenter, due to comments that fall in the right half of the plane; disagreeable to HN mods. But not to digress, it's likely 120 degree BPSK (i.e. QPSK with a DC level for the Q). I'm not in the deep space field (but do RF/Microwave professionally), but the DSN (deep space network) on Earth sends out a carrier with 120 BPSK modulation with PN (pseudo noise) code. The spacecraft transverts and s…

Thank you so much for the information. In case you have any links to share about how DSN works, I'd appreciate. And thank you also for mentioning coherent averaging. I'm more or less familiar with the concept but I've been trying to find out the name of the thing so that I could google on how to implement it (I've been collecting some information for assessing the feasibility of a project involving high-loss antennas…

Uplink Downlink is a good, technical history:

https://www.amazon.com/Uplink-Downlink-History-1957-1997-033...

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