5 ms·

> If amateurs can detect the signal from the Voyager probes with a small dish antenna They can't, at least not for any reasonable definition of small. As I'm w

> If amateurs can detect the signal from the Voyager probes with a small dish antenna They can't, at least not for any reasonable definition of small. As I'm writing this, NASA is listening to Voyager using the DSS-14 antenna of the Deep Space Network, a dish with a 70 meter diameter, and the signal it receives is 10^-19 Watt. That's only 15000 photons per second. Coincidentally the area of that 70 meter dish is also roughly 15000 m^2, so a small dish of 1 m^2 will catch roughly 1 photon per second. Given that the datarate is 40 bits/second, it's physically plain impossible to receive the signal with a small dish. Voyager's security is that it's really far away and you need a big, expensive dish to talk with it.

zamadatix 2y ago
If 70 m is the diameter, not radius, that area is a factor of 4 too high. Should be more like ~3850 m^2. Still physically impossible at that size but it does make the required size a bit more tenable.
- dgfitz 2y ago
  For those using freedom units that is about 200ft diameter, or about 31,000 square feet. This works out to roughly 0.7 acres.
  - vdvsvwvwvwvwv 2y ago
    Funny enough the foot was restandardized to .3048m in 1959. So it is a metric-derived unit. Before that it was a feifdom unit, set by kings.
    - dgfitz 2y ago
      Was a tongue-in-check turn-of-phrase. This place is wound tight apparently.
      - Brian_K_White 2y ago
        Your tangential remark is ok but anyone else's is wound up too tight. OK.
        dgfitz 2y ago
        I was trying to frame the numbers for people who don’t have an engineering background. My mistake.
        lukeck 2y ago
        And they provided an interesting tidbit of information about some of the units mentioned. I didn’t read it as anything negative towards your comment at all. Both your’s and their’s added to the conversation.
        DonHopkins 2y ago
        Oh, now you're just trolling the Apostrophe Nazis! ;)
        47282847 2y ago
        And it made sense for you to then call it “freedom units“ why, of all possibilities?
        wiml 2y ago
        Eh, it's a pretty common tongue-in-cheek way to refer to America's love of a slightly old fashioned system. I wouldn't read much into it.
        47282847 2y ago
        Words matter.
        47282847 2y ago
  - BiteCode_dev 2y ago
    Usually this joke flies but apparently, after the last election, people seem to take it seriously.
- justsomehnguy 2y ago
  Antennas at Goldstone Deep Space Communications Complex Name Diameter Description DSS 12: "Echo" 34m Decommissioned in 2012. DSS 13: "Venus" 34m Beam waveguide antenna (BWG) on altazimuth mount, located in Venus, California. ~910 m2 aperture. -> DSS 14: "Mars" 70m Cassegrain reflector on Alt/Az mount. ~3850 m2 aperture. DSS 15: "Uranus" 34m "High Efficiency" reflector on Alt/Az mount DSS 24, 25, 26: "Apollo" 34 m BWG reflector on Alt/Az mount DSS 27, 28: "Gemini" 34 m BWG reflector on "High Speed" Alt/Az mount https://en.wikipedia.org/wiki/Goldstone_Deep_Space_Communications_Complex#Antennas https://en.wikipedia.org/wiki/Goldstone_Deep_Space_Communica...
  - Retric 2y ago
    To be clear, the heading of that column is Diameter. https://www.jpl.nasa.gov/news/nasas-deep-space-network-looks-to-the-future/ https://www.jpl.nasa.gov/news/nasas-deep-space-network-looks... As a sanity check, the video says the area of the dish is approximately one acre which would be ~4,046m2 and a 35m radius disk is ~3,850 m^2.
sandworm101 2y ago
But you dont need to hear voyager in order to hack it. It just needs to hear you. Nasa needs the big dish to hear voyager's tiny transmitters. Someone wanting to send a disruptive message to voyager could use a massive transmitter and a relatively smaller dish. But you dont even need that. You need just enough outbound signal to jam the legitimate uplink, enough that voyager can no longer tell you from the real signal. That is likely much less than the power needed to send a command. Or you could jam the nasa ground stations. A one-watt transmitter on a carefully positioned cubesat in low orbit would be enough to nullify voyager's real signal. (Setup the orbit to be over the deep space network stations every day as voyager comes into view.)
- manquer 2y ago
  Even then you need a fairly large transmitter. It is quite easy to detect EM transmissions even when they are low energy. This would be incredibly easy to detect. There are plenty of regulations already by FCC, ITU and equivalent on what is allowed on what wavelength which most nations are signatories too. Violating these is already solved by law enforcement, even if a rogue nation state is protecting you it will be handled with big gun diplomacy, America after all has the biggest guns. As xkcd put it, $5 wrench is all it takes no matter how strong your encryption, that works both ways, if a government can find a malicious actor all it takes is $5 wrench to stop you. There is limited value for nation state to protect you from hacking voyager, there is no military or strategic value in it. Dormant satellites in LEO or GEO can be used as kinetic weapons so are lot more valuable. There are also tech solutions like active jamming that could easily be deployed to counteract you that civilized world can use first even if they don't/can't blow you up without risking retaliation from your state sponsor.
  - tivert 2y ago
    > Violating these is already solved by law enforcement, even if a rogue nation state is protecting you it will be handled with big gun diplomacy, America after all has the biggest guns. No one is going to war over ITU regulations or Voyager.
    - 2y ago
iancmceachern 2y ago
It's an air gapped system effectively
- jamiek88 2y ago
  More like heliopause gapped !
- thebruce87m 2y ago
  There is some air in the gap, I suppose.
  - iancmceachern 2y ago
    Thank you. Indeed, it's more accurate to say it is space gapped
deleted 2y ago
[deleted]
tzs 2y ago
> […] a small dish of 1 m^2 will catch roughly 1 photon per second. Given that the datarate is 40 bits/second, it's physically plain impossible to receive the signal with a small dish. Do you just mean plain impossible with the specific type of system used with Voyager, or are making a general argument that all systems that have a 1 photon/second rate cannot carry 40 bits/second of data?
tim333 2y ago
pic of the dish for those curious https://www.planetary.org/space-images/the-70-meter-dss-14-antenna-at-goldstone https://www.planetary.org/space-images/the-70-meter-dss-14-a...
- tim333 2y ago
  Also as seen from Google maps satellite view https://www.google.co.uk/maps/search/+goldstone+dss-14+/@35.425922,-116.8906934,407m/data=!3m1!1e3?entry=ttu&g_ep=EgoyMDI0MTEwNi4wIKXMDSoASAFQAw%3D%3D https://www.google.co.uk/maps/search/+goldstone+dss-14+/@35....
lr1970 2y ago
There is fundamental limit (Shannon limit) on decoding a signal Eb/No = -1.6dB [0] where Eb is energy received per bit of information and No is noise spectral density. This makes it paramount to collect as much energy per bit (Eb) as possible which in turn requires large antennas for far away objects such as Voyager probe. [0] https://en.wikipedia.org/wiki/Eb/N0#Shannon_limit https://en.wikipedia.org/wiki/Eb/N0#Shannon_limit
DonHopkins 2y ago
https://news.ycombinator.com/item?id=34227604 https://news.ycombinator.com/item?id=34227604 DonHopkins on Jan 3, 2023 | root | parent | next [–] John McCarthy trolled me once! When I met him, we were chatting about Stanford, and I mentioned that I really admired that huge radio telescope that you could see around 280 and Page Mill Road in the hills above Stanford. He looked puzzled and confused, and asked "Which huge radio telescope?" I was flustered and explained how you couldn't miss it, right by 280 and Page Mill Road, it's out there in a field, its huge, it's enormous, gigantic I tell you, there's no way you can miss it, bla bla bla... He let me go on and on, describing it, and acted like he had absolutely no idea what I was talking about, like I was crazy for hallucinating a gigantic radio telescope that both of us must have passed zillions of times. Finally he let on and said, "Oh, you mean that SMALL radio telescope???" inamberclad on Jan 3, 2023 | root | parent | next [–] It's just called The Dish, and I mean, it's only medium sized (46 meters) compared to the main antenna at a DSN site (70 meters).
trollied 2y ago
At the current rate of progress, when will it become physically impossibe to receive signals from it?

zamadatix 2y ago

If 70 m is the diameter, not radius, that area is a factor of 4 too high. Should be more like ~3850 m^2. Still physically impossible at that size but it does make the required size a bit more tenable.

dgfitz 2y ago
For those using freedom units that is about 200ft diameter, or about 31,000 square feet. This works out to roughly 0.7 acres.
- vdvsvwvwvwvwv 2y ago
  Funny enough the foot was restandardized to .3048m in 1959. So it is a metric-derived unit. Before that it was a feifdom unit, set by kings.
  - dgfitz 2y ago
    Was a tongue-in-check turn-of-phrase. This place is wound tight apparently.
    - Brian_K_White 2y ago
      Your tangential remark is ok but anyone else's is wound up too tight. OK.
      - dgfitz 2y ago
        I was trying to frame the numbers for people who don’t have an engineering background. My mistake.
        lukeck 2y ago
        And they provided an interesting tidbit of information about some of the units mentioned. I didn’t read it as anything negative towards your comment at all. Both your’s and their’s added to the conversation.
        DonHopkins 2y ago
        Oh, now you're just trolling the Apostrophe Nazis! ;)
        47282847 2y ago
        And it made sense for you to then call it “freedom units“ why, of all possibilities?
        wiml 2y ago
        Eh, it's a pretty common tongue-in-cheek way to refer to America's love of a slightly old fashioned system. I wouldn't read much into it.
        47282847 2y ago
        Words matter.
        47282847 2y ago
- BiteCode_dev 2y ago
  Usually this joke flies but apparently, after the last election, people seem to take it seriously.
justsomehnguy 2y ago
Antennas at Goldstone Deep Space Communications Complex Name Diameter Description DSS 12: "Echo" 34m Decommissioned in 2012. DSS 13: "Venus" 34m Beam waveguide antenna (BWG) on altazimuth mount, located in Venus, California. ~910 m2 aperture. -> DSS 14: "Mars" 70m Cassegrain reflector on Alt/Az mount. ~3850 m2 aperture. DSS 15: "Uranus" 34m "High Efficiency" reflector on Alt/Az mount DSS 24, 25, 26: "Apollo" 34 m BWG reflector on Alt/Az mount DSS 27, 28: "Gemini" 34 m BWG reflector on "High Speed" Alt/Az mount https://en.wikipedia.org/wiki/Goldstone_Deep_Space_Communications_Complex#Antennas https://en.wikipedia.org/wiki/Goldstone_Deep_Space_Communica...
- Retric 2y ago
  To be clear, the heading of that column is Diameter. https://www.jpl.nasa.gov/news/nasas-deep-space-network-looks-to-the-future/ https://www.jpl.nasa.gov/news/nasas-deep-space-network-looks... As a sanity check, the video says the area of the dish is approximately one acre which would be ~4,046m2 and a 35m radius disk is ~3,850 m^2.

sandworm101 2y ago

But you dont need to hear voyager in order to hack it. It just needs to hear you. Nasa needs the big dish to hear voyager's tiny transmitters. Someone wanting to send a disruptive message to voyager could use a massive transmitter and a relatively smaller dish. But you dont even need that. You need just enough outbound signal to jam the legitimate uplink, enough that voyager can no longer tell you from the real signal. That is likely much less than the power needed to send a command. Or you could jam the nasa ground stations. A one-watt transmitter on a carefully positioned cubesat in low orbit would be enough to nullify voyager's real signal. (Setup the orbit to be over the deep space network stations every day as voyager comes into view.)

manquer 2y ago
Even then you need a fairly large transmitter. It is quite easy to detect EM transmissions even when they are low energy. This would be incredibly easy to detect. There are plenty of regulations already by FCC, ITU and equivalent on what is allowed on what wavelength which most nations are signatories too. Violating these is already solved by law enforcement, even if a rogue nation state is protecting you it will be handled with big gun diplomacy, America after all has the biggest guns. As xkcd put it, $5 wrench is all it takes no matter how strong your encryption, that works both ways, if a government can find a malicious actor all it takes is $5 wrench to stop you. There is limited value for nation state to protect you from hacking voyager, there is no military or strategic value in it. Dormant satellites in LEO or GEO can be used as kinetic weapons so are lot more valuable. There are also tech solutions like active jamming that could easily be deployed to counteract you that civilized world can use first even if they don't/can't blow you up without risking retaliation from your state sponsor.
- tivert 2y ago
  > Violating these is already solved by law enforcement, even if a rogue nation state is protecting you it will be handled with big gun diplomacy, America after all has the biggest guns. No one is going to war over ITU regulations or Voyager.
  - 2y ago

iancmceachern 2y ago

It's an air gapped system effectively

jamiek88 2y ago
More like heliopause gapped !
thebruce87m 2y ago
There is some air in the gap, I suppose.
- iancmceachern 2y ago
  Thank you. Indeed, it's more accurate to say it is space gapped

deleted 2y ago

[deleted]

tzs 2y ago

> […] a small dish of 1 m^2 will catch roughly 1 photon per second. Given that the datarate is 40 bits/second, it's physically plain impossible to receive the signal with a small dish. Do you just mean plain impossible with the specific type of system used with Voyager, or are making a general argument that all systems that have a 1 photon/second rate cannot carry 40 bits/second of data?

tim333 2y ago

pic of the dish for those curious https://www.planetary.org/space-images/the-70-meter-dss-14-antenna-at-goldstone https://www.planetary.org/space-images/the-70-meter-dss-14-a...

tim333 2y ago
Also as seen from Google maps satellite view https://www.google.co.uk/maps/search/+goldstone+dss-14+/@35.425922,-116.8906934,407m/data=!3m1!1e3?entry=ttu&g_ep=EgoyMDI0MTEwNi4wIKXMDSoASAFQAw%3D%3D https://www.google.co.uk/maps/search/+goldstone+dss-14+/@35....

lr1970 2y ago

There is fundamental limit (Shannon limit) on decoding a signal Eb/No = -1.6dB [0] where Eb is energy received per bit of information and No is noise spectral density. This makes it paramount to collect as much energy per bit (Eb) as possible which in turn requires large antennas for far away objects such as Voyager probe. [0] https://en.wikipedia.org/wiki/Eb/N0#Shannon_limit https://en.wikipedia.org/wiki/Eb/N0#Shannon_limit

DonHopkins 2y ago

https://news.ycombinator.com/item?id=34227604 https://news.ycombinator.com/item?id=34227604 DonHopkins on Jan 3, 2023 | root | parent | next [–] John McCarthy trolled me once! When I met him, we were chatting about Stanford, and I mentioned that I really admired that huge radio telescope that you could see around 280 and Page Mill Road in the hills above Stanford. He looked puzzled and confused, and asked "Which huge radio telescope?" I was flustered and explained how you couldn't miss it, right by 280 and Page Mill Road, it's out there in a field, its huge, it's enormous, gigantic I tell you, there's no way you can miss it, bla bla bla... He let me go on and on, describing it, and acted like he had absolutely no idea what I was talking about, like I was crazy for hallucinating a gigantic radio telescope that both of us must have passed zillions of times. Finally he let on and said, "Oh, you mean that SMALL radio telescope???" inamberclad on Jan 3, 2023 | root | parent | next [–] It's just called The Dish, and I mean, it's only medium sized (46 meters) compared to the main antenna at a DSN site (70 meters).

trollied 2y ago

At the current rate of progress, when will it become physically impossibe to receive signals from it?