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Voyager 1 stops communicating with Earth

cnn.com

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Re: Voyager 1 stops communicating with Earth

#441

Post by anonymous_sorry »

ekianjo wrote: post #183
anonymous_sorry wrote: post #93

> Initially designed to last five years NASA tech often seems to outlive its initial mission length by a massive margin. The Mars rovers spring to mind. It's incredibly impressive, and almost embarrassing! Surely this isn't accidental. Is the kit massively over-specced? Do the uncertainties and risks necessitate such a depth of redundancy that when stuff goes kinda smoothly the thing lasts 9 times longer than it was…

> NASA tech often seems to outlive its initial mission length by a massive margin NASA tech from the 60s 70s Ftfy

I mentioned the Mars rovers as well.

Re: Voyager 1 stops communicating with Earth

#442

Post by pndy »

nonethewiser wrote: post #226
CSMastermind wrote: post #217

Earlier quoted context omitted.

If I remember correctly Voyager benefitted from a particular alignment of the planets to get multiple slingshot boosts from gravity wells. Part of the appeal of the mission was that it will be a very long time before we could possibly do this again because the planets won't line up correctly and we have no technology to speed the probes up to the velocities that the voyager probes achieved.

> Voyager benefitted from a particular alignment of the planets to get multiple slingshot boosts from gravity wells. What exactly does that get us? It gets further into space faster? It travels faster? Cheaper to launch? I mean if it just means it leaves the solar system 20 years faster or something then it seems like cheaper launches far outweigh those favorable conditions.

This is the Project Lyra [1], where a UK-registered not-for-profit company suggest sending a spacecraft to catch-up with ʻOumuamua object that pass thru solar system in 2017, by using orbital mechanic. Spacecraft set off at right window would speed up using gravity assist maneuver [2] around objects in the solar system and save a lot of fuel to hopefully reach 'Oumuamua in 26 years

[1] - https://en.wikipedia.org/wiki/Project_Lyra

[2] - https://vid.pr0gramm.com/2023/12/11/99b60d87a3679fe0-vp9.mp4

Re: Voyager 1 stops communicating with Earth

#443

Post by Aerbil313 »

puzzledobserver wrote: post #416
taylorius wrote: post #385

Earlier quoted context omitted.

According to Wikipedia, the abrupt change occurs at the point when the solar wind's speed decreases into the subsonic range (speed of sound in the interstellar medium is approximately 100km/s and the sun emits the particles that makeup the solar wind at approximately 400km/s). This transition to a subsonic regime causes compression waves to form, and causes the rapid drop off.

I didn't know that the speed of sound in the interstellar medium is 100 km/s. That seems surprisingly high, given that there's more atmospheric material here on the surface of Earth, and the speed of sound is only about 330 m/s. How can sound travel so fast in the interstellar medium?

https://physics.stackexchange.com/questions/162184/what-is-t...

Re: Voyager 1 stops communicating with Earth

#444

Post by Someone »

hunter2_ wrote: post #352
apitman wrote: post #308

One of my favorite tech legends is that apparently Voyager 1 launched with a Viterbi encoder, even though there was no computer on Earth at the time fast enough to decode it. After a number of years Moore's Law caught up and they remotely switched over to Viterbi for more efficient transmissions.

The notion that encoding/transmitting could be simpler than decoding/receiving is interesting. It reminds me of the way optical drives for many years could write at, say, 48x but read at 8x, such that the majority of time spent was the verification step (if enabled) rather than the burn step. Just speculating, I assume it's because of things like error correction, filtering out noise/degradation. Producing the extra…

The Voyager had an experimental reed-Solomon encoder. Encoding ‘just’ is a lookup table from a n-bit value to a m-bit one with m > n. Such a table takes 2^n × m bits.

Decoding also can be table-driven, but then takes 2^m × n bits, and that’s larger.

For example, encoding each byte in 16 bits (picking an example that leads to simple math), the encoding table would be 256 × 16 bits = 512 bytes and the decoding one 65,536 × 8 bits = 64kB.

Problem for Voyager was that 2^n × m already was large for the time.

Re: Voyager 1 stops communicating with Earth

#445

Post by dcminter »

nemo44x wrote: post #316
apitman wrote: post #308

One of my favorite tech legends is that apparently Voyager 1 launched with a Viterbi encoder, even though there was no computer on Earth at the time fast enough to decode it. After a number of years Moore's Law caught up and they remotely switched over to Viterbi for more efficient transmissions.

I don’t know how well it holds today but for some time it was known that running certain computations on existing hardware would take longer than waiting for new hardware and running when available.

I was working with an optimisation problem based around cplex a few years ago that took about 5 minutes to complete - at the time I worked out that if we'd started the optimisation on a machine 10 years prior, it would have been quicker to just wait until the present day (of this story) and then use the code we were writing because improvements in the algorithm and in the hardware added up to a million-fold improvement in performance! If I remember the timelines correctly I think the original version would still have been running today even.

Re: Voyager 1 stops communicating with Earth

#446

Post by explaininjs »

puzzledobserver wrote: post #416
taylorius wrote: post #385

Earlier quoted context omitted.

According to Wikipedia, the abrupt change occurs at the point when the solar wind's speed decreases into the subsonic range (speed of sound in the interstellar medium is approximately 100km/s and the sun emits the particles that makeup the solar wind at approximately 400km/s). This transition to a subsonic regime causes compression waves to form, and causes the rapid drop off.

I didn't know that the speed of sound in the interstellar medium is 100 km/s. That seems surprisingly high, given that there's more atmospheric material here on the surface of Earth, and the speed of sound is only about 330 m/s. How can sound travel so fast in the interstellar medium?

Basically, since there's so little atmospheric material, any particles that you do set in motion will travel very far in a straight line before they hit another, which is a lot faster than hitting a bunch of particles erratically.

The catch is that you can only transmit very low frequency sounds - ti can be thought of like the variations in travel time for any individual particle drown out any high frequency signal.

Re: Voyager 1 stops communicating with Earth

#447

Post by galeaspablo »

seanhunter wrote: post #423
gorgoiler wrote: post #354

Earlier quoted context omitted.

My life archive is available to my heirs and successors as long as they know the LUKS password for any of the numerous storage devices I leave behind. It’s risky though — the passwords aren’t known to them yet and one logistical slip up means the disk may be unusable. That is, however, until some point in the future when they will have a computer powerful enough to just break the key and feast upon my cat photos, tax…

Only a matter of a really really _really_ long time and an absolutely unimaginably huge amount of energy. All the energy released by converting all mass in the solar system into energy apparently gives a hard physical limit just above 2^225 elementary computations before you run out of gas so brute forcing a 256-bit symmetric key seems entirely unfeasible even if all of humanities resources were dedicated to the prob…

We will be able to crack today’s encryption algorithms in the future because we’ll find flaws in them. In other words, one day brute force won’t be necessary!

Have a look at this post, which illustrates this reality being true for hash functions (where similar principles as symmetric and asymmetric encryption apply). https://valerieaurora.org/hash.html

Notice Valerie specifically calls out, “Long semi-mathematical posts comparing the complexity of the attack to the number of protons in the universe”.

Re: Voyager 1 stops communicating with Earth

#448

Post by Someone »

apitman wrote: post #308

One of my favorite tech legends is that apparently Voyager 1 launched with a Viterbi encoder, even though there was no computer on Earth at the time fast enough to decode it. After a number of years Moore's Law caught up and they remotely switched over to Viterbi for more efficient transmissions.

https://voyager.gsfc.nasa.gov/Library/DeepCommo_Chapter3--14... and https://core.ac.uk/download/pdf/42893533.pdf have some details. (https://ieeexplore.ieee.org/abstract/document/57695 likely does, too, but is paywalled)

What I don’t understand (possibly because I didn’t read them fully) is why they didn’t use the better one from the start and taped its data. Maybe they didn’t trust the Voyager to work yet? (One of those PDFs says this was an experimental system) or didn’t Voyager produce enough data to use its full bandwidth (further away, its signal got weaker, so it needed better error correction and/or better receivers on earth) when it still was relatively close to earth?

Re: Voyager 1 stops communicating with Earth

#449

Post by piokoch »

Voyager is the highest technical achievement of humankind to this day. Amount of knowledge we gained from that shuttle, run by a computer having a power of the computer that we have today in our car keys, is invaluable.

Let it fly in peace, maybe, some day, it will be only reminiscence of our civilization and planet Earth, crossing the universe...

There is a great documentary about Voyager- The Farthest - highly recommended.

Re: Voyager 1 stops communicating with Earth

#450

Post by oneshtein »

skissane wrote: post #258
maccam912 wrote: post #214

Earlier quoted context omitted.

How live is it? Voyager 1 seemed to be shown there just now.

According to the article, they can send commands to Voyager 1, and it executes them, and it is still sending data back - the problem is the data coming back is gibberish (repeated patterns of 0s and 1s). They are still hoping they can work out a sequence of commands to reset its computers and resolve the problem. So it makes sense the DSN is currently talking to it.

For me, it looks like it computer damaged by interstellar radiation, which is much more energetic than solar radiation, so it's unlikely that reset will help.
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