We're still in communication with Voyager 1, which is operating on a grand total of about 20W of RF power; and is currently about 14.5 billion miles away.
At the receiver, you have "minimum detectable signal", MDS, measured in dBm.
At the transmitter, you have power out, measured in dBm. Add transmitting antenna gain, in dB, subtract propagation loss through medium(s), add receiving antenna gain, and if that number is greater than MDS, you win! The Really Great Science in Voyager is the added factor of "coding gain" -- sophisticated error correction codes can give you a many dB adder, at the expense of data rate (nobody cheats Claude Shannon).
https://www.guinnessworldrecords.com/world-records/635980-lo...
Man I would not want to be the one to brick that.
Going on a lot of presumption here (and a bit of optimism...), I would presume "don't brick it" is backed up by an appropriate level of funding to cover the training people receive before they get to touch production. In an optimal scenario (don't be wrong... don't be wrong...) this would cover component-level electrically-accurate (because radiation) logic simulation that everything gets tested on first.
I think there may be other computers, right here on Earth, that may be able to at least compete given those criteria.
[1]: From the linked page:
> The CCS originally ran software written in the Fortran programming language, but this has been continually upgraded since its launch (software updates can be transmitted and installed remotely). The current software is written in a mixture of C and Fortran.
The following is fascinating.
> The age of the computer and its codebase has caused problems for NASA in recent years. In 2015 Larry Zottarelli, the last of the project's original programmers, retired, and it was difficult to find a replacement with such in-depth knowledge of what now seem like ancient hardware and design principles.
So 43 hours 10 minutes 26 seconds minimum, excluding processing time.
That's probably another record... Although I'm pretty sure it can't process ICMPs, so "ping" in the more general sense.
Joking, but thanks for the interesting info (and Frost1x also).
I think an older probe also took the first digital pictures before bitmap images were a thing, they could digitise it at the probe end but had to colour in the pixels on a piece of paper at the other end if I recall correctly. Point is, NASA had to solve a lot of digital communication problems long before they had established terrestrial solutions or before computers were even capable of solving the whole problem on their own.
Then again, even if the timing was reversed, a lot of terrestrial communication protocols have no chance of working properly at the ranges required for space exploration - something I've been meaning to look into is the redundancy requirements over those long distances, since re-transmission is so costly in terms of latency that it probably makes sense to pack as much redundancy into the signal as possible, we already do this with terrestrial communication in the form of various codes, but there's a finer balance between increased bandwidth and the relatively low latency cost of re-transmission in the case of unrecoverable sequences... I'm guessing you want a far lower probability of loss for a 43 hour round trip.
Hello. You've reached the Voyager I spacecraft. We can't answer your ping right now but if you'd like to leave a message, please, do so after the beep. We look forward to servicing your request as soon as possible.
https://www.nasa.gov/feature/jpl/nasa-contacts-voyager-2-usi...
Indeed. If you grow up with your most common radio interactions being an FM car radio and a dumbphone, you get the impression it's entirely about range. Then you buy a drone and find out one pine needle shaves 50% off of your signal strength.
iirc the claimed range is around 8km on the one i have, about 5 miles. I have assuredly gone well over 2km with no issues with control or video feed. This was over a straight highway. I routinely fly around a kilometer away, and the only issues i have is if i launch from an extremely dense patch of pine trees, and only at about 800-900 meters, i will lose video (artifacting for a second), but not control. It's never had to RTH.
In case you're curious about city usage, i have a friend that has one he launches from a culdesac in Orange County and can fly in nearly any direction for about 8 minutes* before he hits a geofence, the drone still functions normally. If there is any issues, he can just fly higher.
The newest newest DJI stuff claims even more ridiculous range, 15km+ over open water, for instance.
If i hadn't used it myself, i wouldn't have believed it, it sounds like BS.
* this is 5-7km depending on the tailwind
That's really awesome though.
That is not accurate. The modified wi-fi some DJI drones use is not reliant on the smartphone/tablet attached to the controller. It's strictly between the drone and the controller, which passes data on to the phone via USB. The drones can be switched into AP mode for faster media downloads, but at that point they lose connection with the controller. Ocusync controllers weigh 390 grams, and that isn't that much considering their build quality and the fact they have two 18650 cells inside.
Is there anything particularly special about the antennae on the spaceship? They must be rigorously aligned to point at Earth, and even a slight knock would spoil everything? Or is it more resilient than that?
If you threw a beach ball from the distance of voyager straight to earth it would eventually make it here.
There is almost perfect vacuum between Earth and every star in the galaxy, and yet they don't appear nearly as bright as the Sun.
At $865 million[1] and 14.5B miles that about 0.034 Euros/Km. 1/20 of what he did in 2005.
1: https://voyager.jpl.nasa.gov/frequently-asked-questions/fact...
In terms of size usually guard interval < slot size < inter-frame space. If propagation exceeds guard interval AND have a channel with lots of echo any communication will be difficult. If propagation exceeds slot timing then coordination between more than 2 devices will be different (high retries/low throughput). If propagation exceeds interframe spacing a two-way wifi connection will not be possible as both stations will think every frame timed out waiting for an ACK.
More info here: https://en.wikipedia.org/wiki/Guard_interval https://en.wikipedia.org/wiki/Distributed_coordination_funct... https://en.wikipedia.org/wiki/Short_Interframe_Space
For really long range propagation on earth, reflections on atmospheric layers are the dominant factor (as there is no line of sights due to the curvature of the planetary surface).
See https://www.sciencedirect.com/topics/engineering/atmospheric... for some nice graphs.
Now this might be significant enough in directional waves with a huge constant multiplier (like a 'ideal' laser with no divergence). Someone can probably give insight on it here.
1. https://www.researchgate.net/publication/270512069_Propagati...