Earth To Voyager 2: After a Year in the Darkness, We Can Talk To You Again (nytimes.com) 70
On Friday, Earth's haunting silence will come to an end as NASA switches that communications channel back on, restoring humanity's ability to say hello to its distant explorer.
Because of the direction in which it is flying out of the solar system, Voyager 2 can only receive commands from Earth via one antenna in the entire world. It's called DSS 43 and it is in Canberra, Australia. It is part of the Deep Space Network, or DSN, which along with stations in California and Spain, is how NASA and allied space agencies stay in touch with the armada of robotic spacecraft exploring everything from the sun's corona to the regions of the Kuiper belt beyond the orbit of Pluto. (Voyager 2's twin, Voyager 1, is able to communicate with the other two stations.)
A round-trip communication with Voyager 2 takes about 35 hours --17 hours and 35 minutes each way....
While Voyager 2 was able to call home on the Canberra site's smaller dishes during the shutdown, none of them could send commands to the probe....
NASA ... did send one test message to the spacecraft at the end of October when the antenna was mostly reassembled.
need to send another voyager mission (Score:5, Interesting)
Re:need to send another voyager mission (Score:5, Insightful)
We've send probes to Pluto, Saturn and multiple ones to Jupiter since then. The grand tour of Voyager 2 was only possible because of an unusual alignment of the planets.
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Alignment matters? See, astrology is real!
Actually, I've read the Grand Tour was scaled back to just Jupiter and Saturn to save money. Voyager 2 was allowed to go on because Voyager 1 found that Titan was too hazy to observe well, so they decided exploring Uranus and Neptune was more important than a second Titan encounter, and adjusted course. The original plan was to bring enough fuel for both probes to observe Ti
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Addendum: The Cassini probe carried a special camera filter and radar to see Titan's surface. The Voyagers didn't have those. The fact one could partially see through the haze using a special filter was not known in Voyagers' day. It was not even known how hazy it was. That's why we explore, and refine on later tries.
Re:need to send another voyager mission (Score:5, Informative)
There is a slightly different story in the reference that the WIkipedia article points to (Butrica, Andrew. "From Engineering Science to Big Science". p. 267. Retrieved September 4, 2015.):
Despite the name change, Voyager remained in many ways the Grand Tour concept, though certainly not the Grand Tour (TOPS) spacecraft. Voyager 2 was launched on August 20, 1977, followed by Voyager 1 on September 5, 1977. The decision to reverse the order of launch had to do with keeping open the possibility of carrying out the Grand Tour mission to Uranus, Neptune, and beyond. Voyager 2, if boosted by the maximum performance from the Titan-Centaur, could just barely catch the old Grand Tour trajectory and encounter Uranus. Two weeks later, Voyager 1 would leave on an easier and much faster trajectory, visiting Jupiter and Saturn only. Voyager 1 would arrive at Jupiter four months ahead of Voyager 2, then arrive at Saturn nine months earlier. Hence, the second spacecraft launched was Voyager 1, not Voyager 2. The two Voyagers would arrive at Saturn nine months apart, so that if Voyager 1 failed to achieve its Saturn objectives, for whatever reason, Voyager 2 still could be retargeted to achieve them, though at the expense of any subsequent Uranus or Neptune encounter.
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The "official" mission was Jupiter and Saturn, as they were not initially budgeted for beyond. They could risk administrative trouble if they sacrificed the primary mission for a secondary one.
Re:need to send another voyager mission (Score:5, Interesting)
The Grand Tour was proposed to Congress and denied as being too expensive. NASA built it anyway, relabeled as a trip to Jupiter and Saturn, and launched it during the only window which allowed the Grand Tour. Once they neared Saturn they went back to Congress and said, "We have this spacecraft which is paid for and working well that can go to two planets that the Soviets can't visit. Will you fund it?" Every day since arrival at Saturn has been a mission extension, every Republican administration has tried to cancel monitoring of Voyager but none have succeeded (so far). Voyager is our only functioning mission outside the heliopause, when it was launched the ability to communicate with anything that far away didn't even exist.
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A lifetime of outrage. I've been watching these systems since their launch. Reagan opposed the Neptune and Uranus mission extensions and did not include them in the budget, Congress restored them. Bush the elder did the same, Bush the lesser wanted them turned off (along with ordering the destruction of the unanalyzed Pioneer and Mariner data, which NASA also foiled).
Re: need to send another voyager mission (Score:2)
Not that i doubt how much of anti science assholes people, and Republicans in particular can be, I'd like some real sources too.
I've googled a bit, but couldn't come up with much. It you have some, I'm interested.
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Leave it to clever nerds to work around the silly office politics of "the suits".
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What about New Horizons? That's heading for deep space and should pass 100 AU in 2038.
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Just in time to hit the Year 2038 bug! :D
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New Horizons' power budget is tighter: when launched, the Voyagers had far more available electric power than NH, and the Voyagers had power-hungry cameras that could be switched off to reduce the power requirement so the difference between starting power and minimal power required for the probe to function is much larger on the Voyagers. The output of the RTG drops a few % each year, and that's what limits the length of the mission.
So NH won't live as long as the Voyagers.
One is enough (Score:2)
One is enough, it will come back in 200 years, maybe in a bit of a rough shape, missing a letter or two, but will carry lots of knowledge.
On a serious note, I remember the excitement growing up in the 80s and we had these intrepid missions reach the outer planets of the solar system for the first time... In the 90s there was the HST excitement, including fixing it, robotic missions to Mars, the ISS... The pace & excitement has not been kept up since then, most of the effort seems to be going to that nev
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JHUAPL has done a proposal for just that [jhuapl.edu]: a new mission to the edge of the solar system. It's planned to use an Oberth-Kuiper [xkcd.com] maneuver to get the speed up to twice that of Voyager.
Most of Voyager's role has been taken over by orbiters. After Voyager's initial reconnaissance, Jupiter and Saturn have been host to flagship missions. Uranus or Neptune are next. The days of flybys for planetary science are over, I suspect. Maybe we'll get a Neptune flyby, but we're seeing viable orbiters being proposed as well.
S
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We have the New Horizons probe that might still function for another 10 years or so:
https://en.wikipedia.org/wiki/... [wikipedia.org]
It will not be able to travel the same distance as Voyagers did, however it still has a lot of power and functioning instruments to explore the outer reaches of the solar system. *IF* we are lucky it might take snapshots of another rock, too.
4 years (Score:3)
How humbling (Score:2)
How Doh! (Score:2)
And it's message when communications resumed were...hey did you guys see that UFO that passed by? Sorry you missed it.
Summary is inaccurate (Score:5, Informative)
NASA didn't "shut down the Australia dish in its Deep Space Network".
They shut down one of the dishes at the Canberra site of the DSN. The Canberra site has a 70-m dish and three 34-m dishes, plus the Parkes radio telescope. The 70-m dish, DSS-43, has a powerful transmitter which makes it the only antenna that can be used to transmit to Voyager 2. This is the antenna that was down for maintenance.
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They will issue a correction, of course.
Just kidding, this is Slashdot.
Johnny Be Goode rides again! (Score:1)
17 hours and 35 minutes each way. (Score:1)
We assume light travels the same speed both way. But currently we cannot prove it. But if it took 10 hours and 35 minutes to get there and 24 hours and 35 minutes back, We would technically have now way to prove that.
I don't say that to put science into question, as with lack of any other evidence we should probably treat light going the same speed in all directions, as it would make the simplest model (Occam's razor). I just find it interesting there isn't a good way to prove it.
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if we sent a ping, and then got back a ping, that would at least let us know the total round-trip time? Then if we know the time one-way, simply subtract to get the other one?
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Not at all, Voyager has its internal clock, as long as your reply ping included that data you certainly could tell. If you want to make sure that it hasn't drifted send your ping with a clock reset command, so that you know exactly what time the signal from Earth was received and exactly what time the reply was sent.
Re: 17 hours and 35 minutes each way. (Score:2)
You can't actually, because there is no way to synchronize the clocks on earth and on Voyager.
Syncing then at launch is useless, because motion can affect them.
Sending a clock resest is useless too, so the math, you have 4 variables for 3 equations.
We assume light speed is uniform in all directions. Our models work well with it, but we can't prove it. https://www.universetoday.com/... [universetoday.com]
Re: 17 hours and 35 minutes each way. (Score:2)
Yes. Space time is affected by motion, so any atomic clock moving is affected too.
GPS satellites have atomic clocks. They tick faster than the same clocks in Earth, for example.
And the equations that describe how motion affect space time depend on, you guessed it, the speed of light.
If you suppose the speed of light is unknown, you can't calculate how the clocks tick relative to each other and so you can't derive the one way speed of light.
The beauty is that models work with both assumptions, and since ther
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You'd have to come up with a reason it travels a different speed, and you'd also have to come up with a reason we can't measure that difference on shorter transmissions. For example, Mars is pretty far away. And we can measure the timing of light travel really, really, really precisely on Earth.
Re: 17 hours and 35 minutes each way. (Score:2)
We can only measure the round trip time, we can't make the one way time without a way to synchronize clocks at both ends.
And we have no way to sync those clocks.
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And we have no way to sync those clocks.
First, we absolutely can sync those clocks on Earth.
Second, we know the drift of extremely-precise clocks, capping the +/- time measurement for things we send to Mars.
Re: 17 hours and 35 minutes each way. (Score:2)
No, from the moment the clocks aren't at the exact same point in space, you can't sync them.
To sync them, you need to signal both clocks at the same time, or to have one signal the other, but that all depends on the one way speed of light, so you can't then use them to calculate the one way speed of light.
Even quantum clock synchronization has similar limits.
Read articles about QCS and the wiki article about the one way speed of light. They have way more info than i could give you.
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Here, lemme quote the part above that you appear to have ignored:
And we can measure the timing of light travel really, really, really precisely on Earth.
So, when talking about syncing clocks on Earth, we're still talking about measurement on Earth.
And again, we have an idea of the possible drift of the clocks we do send to Mars, so that caps the +/- for the drift. Which means if light traveled at a wildly-different speed, we'd exceed that +/-.
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Here, lemme quote the part above that you appear to have ignored:
And we can measure the timing of light travel really, really, really precisely on Earth.
So, when talking about syncing clocks on Earth, we're still talking about measurement on Earth.
If you want to measure the one way speed of light, your clocks need to be distant from each other, even on Earth.
Assuming the speed of light may not be uniform in all directions means that you can't sync clocks that are distant, or that if you try to sync clocks in the same place then move one away, you can't calculate how its movement affects its ticking rate since the equations that describe how movement affect space time depends on the speed of light.
And again, we have an idea of the possible drift of the clocks we do send to Mars, so that caps the +/- for the drift. Which means if light traveled at a wildly-different speed, we'd exceed that +/-.
Nope. Even if you had a clock with absolutely no drift
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Typo: Compared to Earth clocks, GPS satellites' clocks tick slower due to their motion, but faster due to them being further away from Earth gravity well. In totality, they tick faster.
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Re: 17 hours and 35 minutes each way. (Score:1)
Actually, no, there is no reason the theories wouldnâ(TM)t work. As long as it looks symmetric, the theories donâ(TM)t care if light suddenly stops working once it leaves the range of the measurements, as long as the value returns consistently.
Sure itâ(TM)s up there with Russelâ(TM)s teapot but there is no reason to think that the rest of the Universe 300 miles outside earth or hell, the Universe outside of your own physical perception cant be just simulated or suddenly speed up or slow
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various energy equations are based on the speed of light
They're based on the average calculated speed of light, as accurately as we've been able to measure... or, more precisely, the constant c as defined by Einstein, who defined it that way because there is no way we know of to determine an objective inertial frame.
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The Veritasium channel on youtube recently tackled this conundrum: https://www.youtube.com/watch?v=pTn6Ewhb27k [youtube.com]
His take (and Einstein's, apparently): yes, the best you can do is measure round-trip time, and assume the average velocity applies in both directions. The universe (well, relati
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Isra Trap! (Score:2)
Isra Trap!
Fun fact (Score:4, Interesting)
the Voyagers are still among the biggest users of the DSN. They usually get an 8-hour timeslot each day, for live playback of science data. The Voyagers use tape recorders to store information. On Voyager 2 the tape recorder has failed, I'm not sure if the Voyager 1 recorder still works. If it does, the maximum data rate of the radio link may be lower than the lowest playback speed of the tape recorder.
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Do mean currently, or during their planetary encounters? If their tape recorders have failed, they can't cache a whole lot in RAM anyhow.
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Yes, currently. During the planetary encounter they got continuous coverage, and the tape recorders were working until long after the Neptune encounter.
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Although the probes may not be sending a lot of actual data, I imagine they need a really slow bit rate due to the shear distance, stretching the com sessions way out.
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yes, data rate is around 160 bit/s these days. And with the tape recorders inoperative, sending the data out directly is the only way to do it.
Write-Only: We got lucky (Score:2)
Voyager was still able to send routine data during that time, but couldn't receive new commands.
We got lucky, because it had a timer set to go into a keep-safe slumber mode if it didn't get new commands within a set time. They used the half-rebuilt antenna to reset the timer to keep getting data. Fortunately it worked. Covid, you lost this round, you goddam fuzzball!
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I've always thought this was cool.
https://en.wikipedia.org/wiki/... [wikipedia.org]
There are three different computer types on the Voyager spacecraft, two of each kind, sometimes used for redundancy. They are proprietary, custom-built computers built from CMOS and TTL medium scale integrated circuits and discrete components. Total number of words among the six computers is about 32K. Voyager 1 and Voyager 2 have identical computer systems.[33][34]
The Computer Command System (CCS), the central controller of the spacecraft,
Operational imperative (Score:2)
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Merge with cats.
Relay in orbit? (Score:2)
Maybe I've played too much KSP but with the amount of hardware spread out over the solar system why do we not have a large dish in Earth orbit to act as a relay to the ground?
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Putting large things in orbit is very expensive to do, expensive to maintain the hardware, and requires lots of refueling to keep it in orbit. For a very small improvement over ground-based antennas.
Dream Job (Score:2)
I think it would be really cool to be able to say I operate the Deep Space Network.
Dream Food. (Score:2)
Or the Deep Dish Network.
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That would be based in Chicago.
For the last time... (Score:2)
Well sometimes (Score:2)
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What?
The Voyagers are ~130 AU out. Earth's position (which varies by 2 AU over the course of a year) doesn't really matter at that distance, as long as the Sun isn't in the line of sight (which it isn't for the Voyagers, as they're both out of the ecliptic plane now).
They barely even have to adjust Voyager's attitude over the seasons: the beam width of the antenna is large enough that Earth's entire orbit falls within the beam.
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it isn't for the Voyagers, as they're both out of the ecliptic plane now
34 degrees it seems. should be enough.