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View Full Version : Voyager - Would we notice?



Click Ticker
2007-Oct-04, 04:37 PM
Let say some light years away there is an earthlike world. Thousands (millions?) of years ago they sent out a Voyager like probe. The probe is happily cruising along at 20km/s. The probe passes right by our humble planet. Would we even notice?

Given the size and the speed - would one have to be directly looking for a probe travelling that fast to notice it or would it pass by leaving us oblivious to life on another world for another however many years?

Van Rijn
2007-Oct-04, 05:03 PM
Yes, you would have to be looking for it. It would be electronically dead and very small. Remember, cometary debris comes along now and then too. It almost certainly would be missed.

neilzero
2007-Oct-04, 05:12 PM
We might miss it. More likely it would be recorded as one of the hundred tiny asteroids and comets that pass close to Earth each year. If the solar panels were brightened from reflected sunlight we might marvel that so little mass would be even 25th magnitude.
Likely it would pass Earth at 60 km/sec if it came from outside our solar system. It would pick up speed as it's galactic orbit fell toward our sun. That fast would attract our attention, except it would only be close to Earth a few hours, and the flash of reflection from the solar panels would last seconds at the most. Neil

antoniseb
2007-Oct-04, 05:20 PM
We would miss it unless it came within a few thousand miles of Earth AND got lucky as far as photographic evidence.

Argos
2007-Oct-04, 05:45 PM
Well, in order for it to pass at only 20 km/s coming from outside the SS it would have to perform some kind of deceleration burn. IŽd guess such burn would leave an observable EM signature, especially in radio.

astromark
2007-Oct-04, 06:21 PM
" ISS ruptured by space debris" but thats just fiction. we would not be aware of this pioneer type space probe whistling past Earth. If you take the next step down this line of thought what would be the chances of detection if the space craft is not transmitting a signal. Almost 0. Isn't reality booring?... But if it did a retro burn and entered Earth orbit it would get our attention.

Click Ticker
2007-Oct-04, 06:29 PM
" ISS ruptured by space debris" but thats just fiction. we would not be aware of this pioneer type space probe whistling past Earth. If you take the next step down this line of thought what would be the chances of detection if the space craft is not transmitting a signal. Almost 0. Isn't reality booring?... But if it did a retro burn and entered Earth orbit it would get our attention.

I figured as much. I stumbled upon this site a year or two ago after reading a couple hypothetical light speed ideas and other astronomy news and getting all excited thinking we were near some break throughs. I'm very much the uninformed novice - but logical enough that I didn't come in expecting to know anything. You are correct, I did find out how boring reality is - although it's strange how something like astronomy and the geological history of our planet can be so boring and amazing at the same time.

KaiYeves
2007-Oct-04, 09:41 PM
I drew a manga where advanced humans discover a Voyager-type probe in the Oort Cloud of a system with an Earthlike moonlet, visit and get chased by a MIB-type group. More humor than anything else, especially the assistant of the astronomer who found the human ship, thinking it was a meteor.
"This could be the most important moment of either of our lives, Ansi."
"Yeah, but it could also be the last moment of our lives, Dr. Safi. They could be brain-eating aliens like in the movies!"

Neverfly
2007-Oct-04, 10:10 PM
I drew a manga where advanced humans discover a Voyager-type probe in the Oort Cloud of a system with an Earthlike moonlet, visit and get chased by a MIB-type group. More humor than anything else, especially the assistant of the astronomer who found the human ship, thinking it was a meteor.
"This could be the most important moment of either of our lives, Ansi."
"Yeah, but it could also be the last moment of our lives, Dr. Safi. They could be brain-eating aliens like in the movies!"

You mean, "Ameobas."

jlhredshift
2007-Oct-04, 11:28 PM
You are correct, I did find out how boring reality is - although it's strange how something like astronomy and the geological history of our planet can be so boring and amazing at the same time.

I totally agree.

I will find myself reading a paper on Permian strata and thinking "OhYeah, only 251 mya" and then thinking about supper in 30 minutes. I don't think we would see it unless it bit us in the butt.

EvilEye
2007-Oct-05, 01:16 AM
I still believe that the chances of us or them noticing each other...even if looking right at us, are negligeable.

1. All life wouldn't evolve at the same time, nor at the "right" time.

2. No life below technological could be detected from very far away without a probe. And we haven't had any probes landing here even.

3. Distances forbid it... even with science fiction, the likelyhood of someone passing by us near or faster than lightspeed and detecting us is NILL.

4. We just aren't interesting enough for anyone to look at. ..if they are THAT advanced, they would have encountered our types several times, and just shrugged.

Neverfly
2007-Oct-05, 01:22 AM
In another thread someone mentioned the intersting concept that a probe (Like Voyager) that had been travelling in space for a very long time would accumulate a LOT of dust and debris on its surface. Eventually it would become the "core" of it's own asteroid... And you wouldn't even recognize its nature unless you cracked it open.

joema
2007-Oct-05, 03:43 AM
....a Voyager like probe. The probe is happily cruising along at 20km/s. The probe passes right by our humble planet. Would we even notice?...
It probably depends on the trajectory and distance from earth.

The U.S. Space Surveillance Network (SSN) is an array of electro-optical sensors that monitors objects in deep space: http://en.wikipedia.org/wiki/US_space_surveillance_network

It can detect orbital space debris the size of a bolt or screw. It's likely a much larger object like a space probe in a near-earth trajectory could be detected further out.

This paper indicates the limiting sensitivity of one optical SSN sensor is about magnitude 18, which is pretty dim:

http://www.mitre.org/work/tech_papers/tech_papers_03/faccenda_deepstare/faccenda_deepstare.pdf

However mere detection would mean little. It would just be another space debris track -- a few pixels cataloged. We have no quick-reaction capability to rendezvous or inspect it more closely.

Whether it was a space rock or a probe with a message inscribed on the side, we'd never know the difference -- even IF it was detected.

KaiYeves
2007-Oct-06, 05:41 PM
You mean, "Ameobas."
What makes you think there are movies about brain eating ameobas on Vita'minc?

Romanus
2007-Oct-07, 02:35 PM
As others have said, we'd miss it. Something that small would be invisible unless it were very, very close, and the flyby would be blindingly fast; we're talking crossing the Earth-Moon distance in less than two hours.

Hence, as Sagan himself once said, IIRC, any civilization capable of finding--let alone capturing--the Voyagers will almost certainly be far more advanced than we are, all the more so because close flybys to any star are extremely unlikely.

KaiYeves
2007-Oct-07, 08:27 PM
Hence, as Sagan himself once said, IIRC, any civilization capable of finding--let alone capturing--the Voyagers will almost certainly be far more advanced than we are, all the more so because close flybys to any star are extremely unlikely.
Ian Safi would certainly agree. That was mostly the model for his character, with some Milo Thatch (From Atlantis: The Lost Empire) and Nikola Tesla mixed in. Oh, and green skin.

The_Radiation_Specialist
2007-Oct-07, 09:07 PM
Considering we saw it a month before, what measures can we take to capture it? I suppose hitting anything with 20 km/s would shred it into dust. Can we send a mini nuclear engine to give it enough momentum from the opposite direction to slow it down? Or make it orbit the earth.

It would be interesting to see the methods we can use to capture such an object.

Larry Jacks
2007-Oct-08, 04:18 PM
The U.S. Space Surveillance Network (SSN) is an array of electro-optical sensors that monitors objects in deep space: http://en.wikipedia.org/wiki/US_spac...llance_network

It can detect orbital space debris the size of a bolt or screw. It's likely a much larger object like a space probe in a near-earth trajectory could be detected further out.

Not quite. The SSN is a collection of radar and electro-optical (EO) sensors. The EO sensors are primarily the GEODSS units. They're capable of tracking a volleyball-sized object out at geosynch but nothing as small as a bolt or screw. While they sometimes are used to survey NEOs further out, that isn't their mission. They might detect a Voyager-sized spacecraft if it passed fairly close to the Earth but only if it happened while the sensor was enjoying a clear night. GEODSS doesn't work during daylight and it can't see through clouds.

The best chances of detecting a Voyager-sized object would be from those sensors working full time to track NEOs. Even then, it'd have to come pretty close to the Earth to be detected.

joema
2007-Oct-08, 05:21 PM
...They're capable of tracking a volleyball-sized object out at geosynch but nothing as small as a bolt or screw...
I didn't mean to imply they could detect a small screw at GSO distance.

As stated, SSN consists of both electronic and optical sensors. According to this document some of the radars can detect 1 cm objects (presumably in LEO) http://www.fas.org/spp/military/program/track/mccall.pdf

I think the recorded track data of some of these radars were used after the Columbia disaster to evaluate small pieces (a few cm across) that drifted away from the vehicle while in orbit. The goal was to compare the radar data for these to the probable size of an RCC tile fragment.

The OP didn't say what trajectory, so many are possible. If it came pretty close -- up to a few hundred miles, the liklihood of detection is greater.

Agreed the SSN mission is not deep space detection, so it's unclear if a random Voyage-size space probe that came (say) within GSO distance (22,000 mi) would be detected. The radar resolution capability is probably there -- if they knew ahead of time. Whether a random Voyager-size passage at GSO distance would be detected, I'm not sure. I tend to doubt it.

We don't detect all near-earth asteroids, so it seems unlikely we'd detect a much smaller space probe, even if it passed closer than the moon.

But -- mere detection means little. The question implies if it was detected, we'd learn something: ("look there goes an alien probe").

In reality, even IF detected it would be a few pixels (optical or radar), IOW "there went something". Even IF it was detected, we'd never know whether it was a space rock or an alien probe with a message inscribed.

Larry Jacks
2007-Oct-08, 06:25 PM
I didn't mean to imply they could detect a small screw at GSO distance.

Unfortunately, GEODSS doesn't have that kind of resolution at any distance.

I think the recorded track data of some of these radars were used after the Columbia disaster to evaluate small pieces (a few cm across) that drifted away from the vehicle while in orbit. The goal was to compare the radar data for these to the probable size of an RCC tile fragment.

None of the SSN phased array radars would've been able to track pieces falling off of Columbia, at least not after it cross the US coastline. Beale quite likely could've tracked Columbia earlier in the reentry but that might've been before pieces started falling off. None of the other phased arrays look in the right direction. It's possible that the Fence might've seen a few pieces when Columbia crossed its coverage. However, the Fence only looks straight up and can only see things that pass through it.

As for 1 cm resolution, there's only one radar with that resolution and that's only under special circumstances in a particular operating mode. I hesitate to go into the operational details.

Radar coverage out at geosynch is pretty limited. Only a few of the radars can track things out that far and most of them are mechanical trackers instead of phased arrays. This is important because of the coverage areas for different types of radars. Depending on power availability and the range, a phased array radar can set up a "fence" to track whatever passes through. A mechanical tracker can really only detect whatever passes through the area where it's pointing. It's kind of like looking at something through a soda straw - your field of view is really limited. Unless the mechanical tracker is tasked to scan an area (typically by sweeping the antenna in a bow-tie or spiral pattern), the chances of detecting something new and unexpected are really, really slim. An object could pass undetected as close as a degree or two of the radar's boresight by being outside the beamwidth.

In reality, even IF detected it would be a few pixels (optical or radar), IOW "there went something". Even IF it was detected, we'd never know whether it was a space rock or an alien probe with a message inscribed.

If someone were able to track it long enough to determine the trajectory, they might discover that it came from outside the solar system. That would make it very interesting but wouldn't necessarily mean it was an alien probe.

m1omg
2007-Oct-08, 06:55 PM
" ISS ruptured by space debris" but thats just fiction. we would not be aware of this pioneer type space probe whistling past Earth. If you take the next step down this line of thought what would be the chances of detection if the space craft is not transmitting a signal. Almost 0. Isn't reality booring?... But if it did a retro burn and entered Earth orbit it would get our attention.

why are you everywhere telling that everything is booring...NOT everyone needs hyperdrives and 200 suernovas per day in the universe to be amazing

joema
2007-Oct-08, 09:35 PM
....None of the SSN phased array radars would've been able to track pieces falling off of Columbia, at least not after it cross the US coastline...
Just to be clear, I was talking about post-crash evaluation of radar data taken while Columbia was in orbit. The goal was to see if any small object (such as an RCC panel) separated while in orbit.

A small object, likely about 9" x 10", was detected by various space surveillance assets including the SSN, the U.S. Navy Space Surveillance System, and the Air Force PAVE PAWS radar. The details are discussed in the CAIB report.

However this very case illustrates the limitations of current capability. The object was only found after the fact, only because they knew to look for it, and it required exhaustive sifting through mountains of data, including specialized supercomputer radar cross-section analysis.

jlhredshift
2007-Oct-08, 09:42 PM
Just to be clear, I was talking about post-crash evaluation of radar data taken while Columbia was in orbit. The goal was to see if any small object (such as an RCC panel) separated while in orbit.

A small object, likely about 9" x 10", was detected by various space surveillance assets including the SSN, the U.S. Navy Space Surveillance System, and the Air Force PAVE PAWS radar. The details are discussed in the CAIB report.

However this very case illustrates the limitations of current capability. The object was only found after the fact, only because they knew to look for it, and it required exhaustive sifting through mountains of data, including specialized supercomputer radar cross-section analysis.

To turn this around a little, if something(?) wanted to approach covertly, they could??

transreality
2007-Oct-08, 10:39 PM
if the probe started broadcasting its data back to its originating star as it made or soon after the fly-by... could we detect that?

neilzero
2007-Oct-09, 12:32 AM
SETI would possibly detect part of the data transmission, but it would be very weak assuming the probe aimed it's very narrow beam laser and/or microwave beam at it's home planet, the beam would all but surely miss Earth, however about 1% of the beam energy is typicaly scattered in many other directions.
Other than the several projects simular to SETI, I don't think anyone is looking for random signals from space. Neil

KaiYeves
2007-Oct-09, 12:32 AM
if the probe started broadcasting its data back to its originating star as it made or soon after the fly-by... could we detect that?
Yes, could we? I have a SF story where the hero recieves a ransom call at him house. He dials the unknown call number but gets nothing, because the villian is calling from another solar system (They're both something very much like Time Lords.) An alien spaceship that's an ally of our hero nearby intercepts the call and traces it with their "advanced alien tech".

joema
2007-Oct-09, 03:49 AM
To turn this around a little, if something(?) wanted to approach covertly, they could??
Dept of Defense space surveillance maintains close watch on orbital objects for national security reasons and for tracking space debris. Many thousands of small orbital debris objects are tracked and cataloged, since this facilitates identifying new objects. It also helps avoid collisions with manned orbital vehicles like the shuttle and ISS.

It seems unlikely a large object (say the size of a large unmanned space probe) could orbit the earth within several thousand miles for a long time and not be detected, since much smaller objects are detected regularly.

However as already stated, the main DOD space surveillance emphasis on earth orbit, not beyond. I doubt a large space probe passing at 1/2 lunar distance would be seen.

Also the radar assets are at known (or knowable) locations. If an incoming sophisticated robotic or crewed extra-terrestrial space vehicle wished to avoid detection, it could theoretically just avoid entry paths covered by those radars.

astromark
2007-Oct-09, 06:35 AM
why are you everywhere telling that everything is booring...NOT everyone needs hyperdrives and 200 suernovas per day in the universe to be amazing

Whats with you? where did I say that?
Go back and read what I said. :)I have a passion for astronomy and science. If I appeared negative or you think I judge as boring, No. I do not. I enjoy a different point of view.
I am also sure that a passing space probe would or could be detected if it came within a lunar distance of Earth. But would detecting it tell us anything we would want to know. No it would not. As I said previously ' if it did a burn and put itself into orbit. We would know'.

RalofTyr
2007-Oct-09, 09:22 PM
There should be objects going past our solar system faster or slower than everything else here. Ejected comets, asteroids and....planets should swing through our system every so often. However, since no scientist as observed anything extrasolar coming into our system, it is very likely that such and event is rather rare and if an alien voyager like probe pass us, it would be very, very, very, very rare and a coincidence that at this point in time the probe pass earth and not say, a billion yeaars ago.

For all we know an alien probe carrying mircrobes crash into Earth or Mars, seeding the world(s)[ATMS] 4 billion years ago.

EvilEye
2007-Oct-09, 11:46 PM
The problem is the word "rare".

Rare for our short existence. And the lack of evidence if it doesn't cause something we can go back and find.

mugaliens
2007-Oct-10, 03:51 PM
Let say some light years away there is an earthlike world. Thousands (millions?) of years ago they sent out a Voyager like probe. The probe is happily cruising along at 20km/s. The probe passes right by our humble planet. Would we even notice?

Given the size and the speed - would one have to be directly looking for a probe travelling that fast to notice it or would it pass by leaving us oblivious to life on another world for another however many years?

And what if it was a matter/antimatter doomsday device designed for the sole purpose of anhilating curious but intelligent other species who might nevertheless be a potential.

Neverfly
2007-Oct-10, 04:01 PM
And what if it was a matter/antimatter doomsday device designed for the sole purpose of anhilating curious but intelligent other species who might nevertheless be a potential.

Reverse engineer it and send it back to them.
From Earth with love http://www.cosgan.de/images/smilie/liebe/s035.gif

Noclevername
2007-Oct-10, 08:16 PM
if the probe started broadcasting its data back to its originating star as it made or soon after the fly-by... could we detect that?

Building a probe that would still function after such a journey is itself a nontrivial problem. As for detecting a transmission, it would depend on a number of factors like signal strength, frequency, how tight a beam, how close they came to us before signalling, and whether there was anything between us and them (if the signal was sent when the probe was on the far side of the sun from Earth, for example.).

transreality
2007-Oct-10, 11:03 PM
What would be the point of sending a probe that didn't send information back, all ours to other worlds do and when they stop the mission is over. I would imagine that a interstellar probe would have to have very powerful transmission.

Possibly such a probe would even have detectable sensors such as a powerful radar, but if it is travelling at interstellar speeds (unlikely to be able to slow to anything like orbital velocity) maybe it would not be possible to deploy them, or obtain useful information in the time such a machine would have near the planet.

KaiYeves
2007-Oct-11, 01:42 AM
From Earth with love
Similar to how when I fired the proton torpedo that destroyed the Death Star in that arcade game:
"Here you go, Sideous!" <Blows kiss>
Presses button.

Kaptain K
2007-Oct-11, 11:33 AM
What would be the point of sending a probe that didn't send information back, all ours to other worlds do and when they stop the mission is over. I would imagine that a interstellar probe would have to have very powerful transmission.

We (currently) have 4 'interstellar" probes. Not one of them is sending information. Of course, they were not intended to be interstellar. After their original missions, they just kept on going.

New Horizons will be number 5.

Ray C.
2007-Oct-11, 02:24 PM
Such an object might be identifiable as artificial, if we saw it at all. Consider J002E3 (http://en.wikipedia.org/wiki/J002E3): a spectrometer shows it to be coated with titatnium dioxide. It is thought to be the third stage of Apollo 12.

mugaliens
2007-Oct-11, 03:27 PM
Reverse engineer it and send it back to them.
From Earth with love http://www.cosgan.de/images/smilie/liebe/s035.gif

That's assuming, of course, that we could even detect it... By the time it gets to us it could be travelling at .3 c. They could have shot one towards every star within 100 ly, with passive sensors to listen for non-naturals on all possible bands. If that were the case, it would have been able to spend the last third of it's journey identifying that the sounds were coming from planet Earth, adjust course, and detonate shortly after entering our atmosphere, frying our planet.

Of course we've sent a few signals from our Moon. Wouldn't that be a hoot it it wasn't so smart and all of a sudden one night we saw half the moon melt in a spectacular explosion?

I can see use sending a message back: "Ha, ha, you missed us!"

But from Mars...

Naturaly, we'd put the squash on all radiated communication, going strictly fiber optic or tight line-of-light, along with bogus transmitters broadcasting everything we could get our hands on from orbit around Mars.

Naturally, the next one they'd send would be a much larger weapon.

neilzero
2007-Oct-11, 10:18 PM
Just the kinetic energy of a ten ton probe hitting Earth's atmosphere at 0.3 c is equivelent to a H bomb. Odds are extremely slim it would hit our atmosphere by accident.
It is also very unlikely that a probe would fly through the very narrow beams we use for space and GEO satellite communication. Some of the signals that leak from wide beam surface communication would be detectable, very briefly a million miles from Earth, if the probe has very advanced SETI type capability. The latter is quite predictable, so we could minimse Earth's detectability at a cost of a few billion dollars per year. Neil

RalofTyr
2007-Oct-11, 10:48 PM
The easiest why to kill us was to attack our world when they existed, a billion years ago, however, they didn't think about it and they've been extinct for about billion years. Their ruined space stations might fly by...

EvilEye
2007-Oct-12, 01:57 AM
The easiest way to describe why we never find another civilization....

think of a Chiminea. (fireplace)

now think of the sparks coming out of it.

Now try to imagine two of those sparks having life ever running across each other from the time you started the fire and before it goes out.