| ▲ | polalavik 6 hours ago |
| Free space pathloss for rf signals is proportional to 1/r^2, absolutely bonkers we can get anything from voyager. |
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| ▲ | rnhmjoj 5 hours ago | parent | next [-] |
| 1/r² is for an isotropic radiator, but Voyager 1 mounts (thankfully) a high gain directional antenna. The gains seem to be 36dBi or 48dBi, depending on the frequency [1]. This means that when pointed towards Earth, the signal power is actually between 4000 to 63000 times stronger than what that formula would give you. It's still tiny, but not as bad as that would suggest. [1]: https://space.stackexchange.com/questions/65801/what-are-the... |
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| ▲ | jacquesm 3 hours ago | parent | next [-] | | No, it is for any radiator. The gain of the antennas has absolutely nothing to do with the free path loss, it just changes the effective radiated power or the concentration effect of the antenna because of antenna related gains. Every kind of antenna has its own specific gain and corresponding losses diagram based on which way the source is relative to the antenna, with the baseline being an omnidirectional radiator (which no antenna really is, but we assume it is). GP was very specific when they mentioned free path loss: the implication is that if you know what free path loss is then you also know that those losses are accurately modeled with that formula, no matter how large your ERP or receiver antenna gain is. At those distances it would make zero sense to use an omnidirectional antenna you will need every bit of gain you can get. | |
| ▲ | robotresearcher 5 hours ago | parent | prev [-] | | For clarity, it’s still proportional to 1/r², but with a much larger multiplier than one. | | |
| ▲ | debo_ 3 hours ago | parent [-] | | This is a practical big-O notation question just waiting to happen. | | |
| ▲ | jacquesm 3 hours ago | parent [-] | | They're totally correct though. Besides that, the performance of this system is incredible and gggp seems to pooh-pooh that. |
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| ▲ | freedomben 5 hours ago | parent | prev [-] |
| And with 50 year old tech! I do wonder if humanity will get to a point where we can retrieve the spacecraft at some point in the future (cue Star Trek fantasies) |
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| ▲ | bonzini 5 hours ago | parent | next [-] | | Technically, the receivers need not use 50 years old tech. I am saying that not to be annoying but because I wonder how much that matters. | | |
| ▲ | cryptonector 4 hours ago | parent | next [-] | | Indeed, it could have been obsolete tech as of launch. That's typically how it goes. | | |
| ▲ | absoflutely 3 hours ago | parent [-] | | I believe they meant that the receivers/transmitters on Earth are likely newer than 50 years old. And you're also probably right that the hardware installed on the voyager could be several years older than the launch date of the craft | | |
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| ▲ | 5 hours ago | parent | prev [-] | | [deleted] |
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| ▲ | deadnomore 5 hours ago | parent | prev [-] | | I would prefer they just maintain it as long as possible and maybe deploy a proxy for earth that trails behind it indefinitely once it’s finally out of range. Let’s set an unbreakable record. |
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