NASA's Voyager 2 survives glitch, gets back to interstellar science

SelfSim

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What amazes me is that the signal is strong enough for the radio stations to be able to pick it up. They're supposed to be around 18 billion kilometres away.

I lifted this off the following site - How Does NASA Communicate With Spacecraft? | NASA Space Place – NASA Science for Kids
Yes. I think the Voyager 1 transmitter power is around a mere 22 Watts and its downlink bit rate is about 160bps. The Mars Reconnaisance Orbiter is around 100 Watts and its downlink bit rate is about 6Mbps. There are many other variables needed to be taken into account in order to make comms with remote probes feasible, not the least of which is the size of the spacecraft antenna (and the receiving earth station antenna size).

Based on Voyager's comms link design, I once calculated that the needed Earth Station antenna size to receive messages from a Voyager type spacecraft at a paltry 1 light year distant from Earth(!), would require an effective earth station antenna size of 50kms in diameter!
 
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Bob Crowley

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Yes. I think the Voyager 1 transmitter power is around a mere 22 Watts and its downlink bit rate is about 160bps. The Mars Reconnaisance Orbiter is around 100 Watts and its downlink bit rate is about 6Mbps. There are many other variables needed to be taken into account in order to make comms with remote probes feasible, not the least of which is the size of the spacecraft antenna (and the receiving earth station antenna size).

Based on Voyager's comms link design, I once calculated that the needed Earth Station antenna size to receive messages from a Voyager type spacecraft at a paltry 1 light year distant from Earth(!), would require an effective earth station antenna size of 50kms in diameter!

Which means that if the SETI search is serious. the alleged aliens would need to be transmitting on extremely high power, or otherwise have moved quite close to earth, prior to putting in a super galactic silk road highway with earth to be demolished because it's in the way.

I'll wait.

While I'm at it, despite all the alleged sightings of UFO's, funny how you never hear that space stations have picked up their radio chit chat. Apparently every single one of them has a policy of non-communication in earth orbit.

What's the military term - "radio silence", "radio blackout"?
 
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SelfSim

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Which means that if the SETI search is serious. the alleged aliens would need to be transmitting on extremely high power, or otherwise have moved quite close to earth,
Other alternative technologies for SETI searches have been considered to overcome some design issues, such as: deep space laser communications, or even laser comms combined with strategic placement of detectors to take advantage of gravitational lensing, (although the physical placement at 550AUs, is a very tough problem).

(Laser comms trials have been conducted and demonstrated as being feasible on recent local space probes however .. and looks set to become more widely used for this purpose).

Bob Crowley said:
While I'm at it, despite all the alleged sightings of UFO's, funny how you never hear that space stations have picked up their radio chit chat. Apparently every single one of them has a policy of non-communication in earth orbit.

What's the military term - "radio silence", "radio blackout"?
Have you considered our own usage of encypted spread spectrum (RF) signals (which would appear as noise to us if ETIs used such techniques)?

I'm not defending SETI's directed searches for ETIs. However, I do consider SETI as making returns to science when considered as actually being a long range (deep space) communications research institute, rather than an organisation searching solely for ETIs.
 
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Bob Crowley

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I'm sure no expert in communication technology, but I would imagine if you're going to use lasers which would need to be in a straight line to retain signal strength, any two UFO's would have to know exactly where the other one was at all times, so they could direct their signals with pinpoint accuracy, otherwise you'd have the same issue of signal spread that we do with radio waves.

Even if a UFO used encrypted spread RF signals, one would think that with the technology available today, at least one space station would pick up the fact that something at such and such an altitude was sending out radio noise, and it's not one of our satellites.
 
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SelfSim

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I'm sure no expert in communication technology, but I would imagine if you're going to use lasers which would need to be in a straight line to retain signal strength, any two UFO's would have to know exactly where the other one was at all times, so they could direct their signals with pinpoint accuracy, otherwise you'd have the same issue of signal spread that we do with radio waves.
Sure .. its an issue alright (referred to as Acquisition, Tracking and Pointing - ATP). Some folk propose that he might continuously keep transmitting his position co-ordinates relative to nearby pulsars in order to keep others updated on his expected location (and for them to use that information for pointing their laser detectors).

Bob Crowley said:
Even if a UFO used encrypted spread RF signals, one would think that with the technology available today, at least one space station would pick up the fact that something at such and such an altitude was sending out radio noise, and it's not one of our satellites.
Depends on the design of the antenna and how widespread the tx spectrum was. If an isotropic radiating antenna was used, then I'd think it would be very difficult to isolate its location in a background of RF noise.
 
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SelfSim

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Here ya go .. co-incidentally, just announced (March 6th):
New telescopes aim to detect extraterrestrial intelligence
PANOSETI explores the universe at billionth-of-a-second time scales—a time scale that has not been examined well to date, agreed Dan Werthimer, chief technologist at UC Berkeley's SETI Research Center and co-investigator.
...
When finally assembled, PANOSETI will be the first dedicated observatory capable of constantly searching for flashes of optical or infrared light. Such pulsed signals occurring on nanosecond-to-second time scales, may be from either artificial origin (e.g., extraterrestrial communication) or astrophysical phenomena (e.g., counterparts to fast-radio bursts).
...
.. according to a recent article in The Guardian, Jill Tarter, an emeritus researcher at the SETI Institute, discussed PANOSETI at the recent American Association for the Advancement of Science (AAAS) conference in Seattle. Tarter noted that with its anticipated vast view of the sky, the instrument is positioned to uniquely spot signals like flashes from faraway lasers.

"The goal is to basically look for very brief but powerful signals from an advanced civilization. Because they are so brief, and likely to be rare, we plan to check large areas of the sky for a long period of time," said Werthimer, who has been involved with SETI for the past 45 years.
 
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SelfSim

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I read the article. OK. Now suppose they pick up signs of ET ten million light years away.

What next? Send a signal back, knowing that it might arrive in ten million years time, if they're lucky?
I suspect we share a common view on all this.
Supposedly humankind's entire 'worldview' will shift beyond recognition upon finding evidence of ETs ... Beats me why, and how all that works though?
 
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Bob Crowley

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I suspect we share a common view on all this.
Supposedly humankind's entire 'worldview' will shift beyond recognition upon finding evidence of ETs ... Beats me why, and how all that works though?

I agree with you. We can't be trusted to treat each other and existing animal life fairly. What makes us think we'd be any better if we found alien life?
 
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FrumiousBandersnatch

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I suspect we share a common view on all this.
Supposedly humankind's entire 'worldview' will shift beyond recognition upon finding evidence of ETs ... Beats me why, and how all that works though?
There are various ideas - the most optimistic hope it will make humanity scrub up nice in case of visitors, the somewhat less optimistic hope it will unite humanity against a potential common enemy, some neutrals hope that knowing we're not unique will bring us down a peg or two, some neutrals hope that having company will cheer us up, and the pessimists fear that it will only encourage us to continue trashing the place, because there's plenty more where that came from...

Two possibilities exist: either we are alone in the Universe or we are not. Both are equally terrifying.
― Arthur C. Clarke
 
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SelfSim

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.. hope it will make humanity .. hope it will unite humanity .. hope that knowing .. hope that having company .. fear that it will ...
So much 'hope' and 'fear'! .. Not a good basis to start doing rational science from!
FrumiousBandersnatch said:
Two possibilities exist: either we are alone in the Universe or we are not.
Whatever happened to the "don't know" possibility?
Isn't that just as real, (ie: exists), as his assertion of 'two possibilities'?
 
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FrumiousBandersnatch

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So much 'hope' and 'fear'! .. Not a good basis to start doing rational science from!
Humankind's worldview has never been a good basis for rational science...

Whatever happened to the "don't know" possibility?
Isn't that just as real, (ie: exists), as his assertion of 'two possibilities'?
It was an ontological statement rather than an epistemological one.
 
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SelfSim

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FrumiousBandersnatch said:
It was an ontological statement rather than an epistemological one.
.. one which serves only the purpose of reinforcing the flimsy belief of: 'truth exists' .. whereas we are discussing how scientists go about deciding that .. by ignoring such beliefs.

There is nothing useful about scientists ignoring the role their own minds play, when forming conclusions based on test results and in this case, there are no results.
 
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FrumiousBandersnatch

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.. one which serves only the purpose of reinforcing the flimsy belief of: 'truth exists' .. whereas we are discussing how scientists go about deciding that .. by ignoring such beliefs.

There is nothing useful about scientists ignoring the role their own minds play, when forming conclusions based on test results and in this case, there are no results.
I suspect he was speaking less as a scientist than a philosopher and educator, providing an intuition-pump, a jumping-off point for thinking along divergent lines.
 
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FrumiousBandersnatch

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'An intuition pump' eh?
What sort of 'thing' are you having that as being?
It's an idea - often a thought experiment, sometimes just a pithy aphorism - intended to spark philosophical intuition into a subject or problem. They can range from Zen koans to philosophical zombies.
 
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SelfSim

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Co-incidentally, recently announced on their website, as from March 31st, 2020:
Seti@home is on Pause. Unfortunately, it’s not Because They’ve Discovered Aliens
And after twenty years, the program recently announced that it has gone into hibernation. The reason, they claim, is that the program’s network has become too big for its own britches and the scientists behind it need time to process and share all the results they’ve obtained so far.
...
“the volunteer computing part of SETI@home will stop distributing work and will go into hibernation.”
The reasons for this, they explain, are twofold:
1) Scientifically, we’re at the point of diminishing returns; basically, we’ve analyzed all the data we need for now.

2) It’s a lot of work for us to manage the distributed processing of data. We need to focus on completing the back-end analysis of the results we already have, and writing this up in a scientific journal paper.
 
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