Detection of 20 watt trasmitter at 11 Billion miles

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sideranautae
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Detection of 20 watt trasmitter at 11 Billion miles

Postby sideranautae » Thu Sep 11, 2014 6:25 pm

Voyager (recently left our solar system) had its location detected & pinpointed in about 1 second by a terrestrial TL 7 radar telescope.

For those that understand how little power 22 watts is and understand the inverse square concept, this should give you an idea of what chance your players will have if trying to hide from a Military passive sensor equipped ship when they are in a standard civilian spaceship.

Basically, a 0% chance...
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Infojunky
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Re: Detection of 20 watt trasmitter at 11 Billion miles

Postby Infojunky » Thu Sep 11, 2014 9:34 pm

sideranautae wrote:Voyager (recently left our solar system) had its location detected & pinpointed in about 1 second by a terrestrial TL 7 radar telescope.

For those that understand how little power 22 watts is and understand the inverse square concept, this should give you an idea of what chance your players will have if trying to hide from a Military passive sensor equipped ship when they are in a standard civilian spaceship.

Basically, a 0% chance...
As long as they know the general neighborhood (within a arcsecond or two) and emitted signal to sort out from background, and hours or days to sort it all out in the post processing.
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Re: Detection of 20 watt trasmitter at 11 Billion miles

Postby sideranautae » Thu Sep 11, 2014 9:49 pm

Infojunky wrote:
sideranautae wrote:Voyager (recently left our solar system) had its location detected & pinpointed in about 1 second by a terrestrial TL 7 radar telescope.

For those that understand how little power 22 watts is and understand the inverse square concept, this should give you an idea of what chance your players will have if trying to hide from a Military passive sensor equipped ship when they are in a standard civilian spaceship.

Basically, a 0% chance...
As long as they know the general neighborhood (within a arcsecond or two) and emitted signal to sort out from background, and hours or days to sort it all out in the post processing.
Um, no. It takes seconds. And only takes a general direction to look in. Within the solar system at that wattage (or higher) there is no other signals.

Nice try though. :lol:
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Infojunky
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Re: Detection of 20 watt trasmitter at 11 Billion miles

Postby Infojunky » Thu Sep 11, 2014 10:05 pm

sideranautae wrote:
Infojunky wrote:
As long as they know the general neighborhood (within a arcsecond or two) and emitted signal to sort out from background, and hours or days to sort it all out in the post processing.
Um, no. It takes seconds. And only takes a general direction to look in. Within the solar system at that wattage (or higher) there is no other signals.
It so helps if you know where to look. You other assumptions are wildly optimistic...
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Re: Detection of 20 watt trasmitter at 11 Billion miles

Postby sideranautae » Thu Sep 11, 2014 10:10 pm

Infojunky wrote:
sideranautae wrote:
Infojunky wrote:
As long as they know the general neighborhood (within a arcsecond or two) and emitted signal to sort out from background, and hours or days to sort it all out in the post processing.
Um, no. It takes seconds. And only takes a general direction to look in. Within the solar system at that wattage (or higher) there is no other signals.
It so helps if you know where to look. You other assumptions are wildly optimistic...

:lol: Nope. Real life happenings.

Nice try though.
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hdan
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Re: Detection of 20 watt trasmitter at 11 Billion miles

Postby hdan » Thu Sep 11, 2014 10:19 pm

It might be interesting to know what sorts of antennae can receive that signal. Presumably, it's those gigantic, expensive radio telescopes. How about a (real world) naval warship? Can those detect that signal?
/hdan
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Re: Detection of 20 watt trasmitter at 11 Billion miles

Postby sideranautae » Thu Sep 11, 2014 10:23 pm

hdan wrote:It might be interesting to know what sorts of antennae can receive that signal. Presumably, it's those gigantic, expensive radio telescopes. How about a (real world) naval warship? Can those detect that signal?
Under 60 miles of atmosphere, Van Allen belts, magnetosphere and trapped solar particles it takes a medium sized expensive radio telescope. In outer space, a US naval ship (Aegis) could do it.
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Re: Detection of 20 watt trasmitter at 11 Billion miles

Postby phavoc » Thu Sep 11, 2014 10:41 pm

sideranautae wrote:
Infojunky wrote:
sideranautae wrote:Voyager (recently left our solar system) had its location detected & pinpointed in about 1 second by a terrestrial TL 7 radar telescope.

For those that understand how little power 22 watts is and understand the inverse square concept, this should give you an idea of what chance your players will have if trying to hide from a Military passive sensor equipped ship when they are in a standard civilian spaceship.

Basically, a 0% chance...
As long as they know the general neighborhood (within a arcsecond or two) and emitted signal to sort out from background, and hours or days to sort it all out in the post processing.
Um, no. It takes seconds. And only takes a general direction to look in. Within the solar system at that wattage (or higher) there is no other signals.

Nice try though. :lol:
That's not entirely correct. Without explaining exactly HOW it works it's a fallacious statement.

First off we are talking about a spacecraft that WANTS to be heard. To this end NASA developed the Deep Space Network. These are a series of antenna's that are 120 degrees apart spread around the globe. The antenna's are HUGE. They are also dedicated. The antenna's that communicate with Voyager do so quite precisely:

The antennas on Earth must be able to track at very precise rates — at thousandths of a degree per second — to remain pointed at the spacecraft as the Earth is rotating at 0.004 degrees per second.

The distant spacecraft stay within the view of a single DSN station for lengths of time from 10 to 12 hours.

Precision pointing of a deep-space antenna is critical. An antenna can see only a small portion of the sky and must be pointed directly at a spacecraft, whether receiving data or transmitting commands. Imagine looking at the sky through a soda straw.

Source: http://www.spacetoday.org/SolSys/DeepSp ... twork.html

Secondly, the probes transmit on a frequency in the 8Ghz range and there isn't a lot of interference at this frequency (natural or man-made). The signals then have to run through a very sensitive amplifier.

Which, for this discussion purpose, you have to be looking EXACTLY in the right place for any passive detection to work. And you'd have to have continuous coverage (i.e. multiple stations) to account for orbits and such. Since the people on Earth know precisely where Voyager is going to be at any given time, they can essentially cheat when it comes to this. I'm pretty sure most invaders are not going to be sending you a "Hey, over here!" transmission if they plan on stooging around your system.

While it IS technically feasible, it's not at all practical. A system would need thousand, or even tens of thousands of detection stations scanning space. It would be hugely expensive and really not worth it. Say you found something at the orbit of Jupiter. It's still days away transit wise by high-G ship from Earth. Even if you had something in the area, it's hours for the radio transmission to reach a ship, and by then the object could be 100,000s of thousands of km's away, hidden again in the vastness of space.

I know it's a popular tagline "There's no stealth in space", but that's kind of a silly argument. First off we've never tried to do it. Secondly who knows what technology will come about to make it possible. We said "stealth isn't possible", except now we are finding ways around that. We've said "you can't hide heat", but what if you could? Or maybe you took a spacecraft, cooled it's surface to the ambient temperature around it, and then took the heat and converted it to energy, stored it internally, or beamed it out into space via microwaves (or heck, used it to power your lights?). Since we are talking about a game that involves skirting the laws of FTL travel and can generate artificial gravity, pretty much anything would be possible.

Or at least to Grandfather it is.
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Re: Detection of 20 watt trasmitter at 11 Billion miles

Postby dragoner » Thu Sep 11, 2014 11:05 pm

phavoc wrote:
I know it's a popular tagline "There's no stealth in space", but that's kind of a silly argument. First off we've never tried to do it. Secondly who knows what technology will come about to make it possible. We said "stealth isn't possible", except now we are finding ways around that. We've said "you can't hide heat", but what if you could? Or maybe you took a spacecraft, cooled it's surface to the ambient temperature around it, and then took the heat and converted it to energy, stored it internally, or beamed it out into space via microwaves (or heck, used it to power your lights?). Since we are talking about a game that involves skirting the laws of FTL travel and can generate artificial gravity, pretty much anything would be possible.
Exactly, what we know about space could fit in a thimble, we even lack a unified theory. For stealth, maybe just wrap the ship in space itself, so for all intensive purposes, it isn't there. For heat, use the extra dimensions as dimensional heat coils, dumping it there, if not, as you wrote, using it as power, thermocouples at least, to direct energy conversion. Science is fine with proof of impossibility, but with what is known now, it isn't there. So the possibilities are endless.

Another thing I find humorous is that even without stealth in space, what are the options? One might know enough to prepare their defenses, or just to surrender.
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Re: Detection of 20 watt trasmitter at 11 Billion miles

Postby phavoc » Thu Sep 11, 2014 11:16 pm

Never give up! Never Surrender!!

Run away! Run away!

Never trust a harmless looking bunny... http://www.youtube.com/watch?v=92gP2J0CUjc
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Re: Detection of 20 watt trasmitter at 11 Billion miles

Postby dragoner » Thu Sep 11, 2014 11:36 pm

phavoc wrote:Never give up! Never Surrender!!

Run away! Run away!

Never trust a harmless looking bunny... http://www.youtube.com/watch?v=92gP2J0CUjc
Yeah, or you line up for the decisive battle like in High Guard.

Traveller wins again. 8)
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Re: Detection of 20 watt trasmitter at 11 Billion miles

Postby sideranautae » Thu Sep 11, 2014 11:45 pm

phavoc wrote:Never give up! Never Surrender!!

Run away! Run away!

Never trust a harmless looking bunny... http://www.youtube.com/watch?v=92gP2J0CUjc
One of my all time favorites!
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Re: Detection of 20 watt trasmitter at 11 Billion miles

Postby ieqo » Fri Sep 12, 2014 2:28 am

Amatuer radio enthusiasts routinely make intercontinental contacts under QRP conditions which break down to thousands of miles per watt of transmitter power using rudimentary antennae. So the news, while impressive, is not particularly surprising. They know what frequencies to camp, which direction to look, and what signals to look for. Frankly it'd be news if they didn't detect the signals.
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Re: Detection of 20 watt trasmitter at 11 Billion miles

Postby sideranautae » Fri Sep 12, 2014 5:11 am

ieqo wrote:They know what frequencies to camp, which direction to look, and what signals to look for. Frankly it'd be news if they didn't detect the signals.
No. It was a random pick up. No previously known data.
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Re: Detection of 20 watt trasmitter at 11 Billion miles

Postby Ash247 » Fri Sep 12, 2014 1:44 pm

sideranautae
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Re: Detection of 20 watt trasmitter at 11 Billion miles

Postby sideranautae » Fri Sep 12, 2014 2:50 pm


Wasn't referring to the VLBA. Nice article though. The example I'm using happened at a US based 12 meter 'scope.
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phavoc
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Re: Detection of 20 watt trasmitter at 11 Billion miles

Postby phavoc » Fri Sep 12, 2014 4:06 pm

sideranautae wrote:

Wasn't referring to the VLBA. Nice article though. The example I'm using happened at a US based 12 meter 'scope.
If you are referring to communicating with Voyager, none of the NASA antenna's are that small.

Each complex has a:

111-ft. diameter high efficiency antenna
111-ft. beam waveguide antenna (Goldstone has three of these)
85-ft. antenna
230-ft. antenna

Five of those 111-ft. beam waveguide antennas were added to the sites at the end of the 1990's — three at Goldstone and one each at Madrid and Canberra. Because of a growing demand for DSN services, another antenna was under construction at Madrid.

Not to mention that NASA (and anyone else) can predict pretty much where Voyager is at any given time. It's not 100% precise, but close enough.
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Re: Detection of 20 watt trasmitter at 11 Billion miles

Postby Rikki Tikki Traveller » Fri Sep 12, 2014 9:58 pm

He didn't say "communicated with Voyager" he said "DETECTED Voyager".

Take out all the rotational compensation from a ground-based unit and it becomes a lot easier. AGREED, Voyager is trying to be detected, but a normal civilian transponder is also going to be trying to be detected. Turning off your transponder automatically means you are a pirate or smuggler...

However, if a ship could go "radio silent" it would only have to worry about the heat signature and the neutrino signature etc. which are harder to detect at TL-7 and probably still hard at higher TL's.

NOW, my counter-argument...

How many ships/probes are going to be local space around a typical TL-7 world within an interstellar setting. If present-day Earth was contacted by the Vilani (you they are right there at Barnard's Star right?) I would suspect dozens of ships at a time would be somewhere inbound or outbound. So there would be a lot more 'noise' at those unique frequencies of energy put out by spaceships and their communicators. By TL-9, near-space is very busy and it might be quite likely that a ship could hide in the background noise of a busy star system. Think of people whispering in a crowded dining room. COULD they be detected, yes, but it will be difficult and there will be a lot of interference from other conversations - ASSUMING you can't use a directional microphone (since you don't know exactly where they are in the room...)

STILL - I think it makes for an interesting idea. Most RPGs assume it is pretty hard to detect a ship in interplanetary space, but actually, it is likely quite easy - doesn't mean you know anything about them other than "they are over there". Also, detecting them like this doesn't give you distance, only direction until you can triangulate or have another means of determining their signal strength, you can't figure out how far away they are.
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Re: Detection of 20 watt trasmitter at 11 Billion miles

Postby enderra » Sat Sep 13, 2014 1:09 pm

I thought the question of "stealth in space" had been settled decades ago. There is none.

(Of course, space opera natural laws behave differently so we always have that retreat.)

That said, this was at TL8 if it happened recently, not TL7, but that's a minor point.
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Re: Detection of 20 watt trasmitter at 11 Billion miles

Postby phavoc » Sat Sep 13, 2014 3:12 pm

enderra wrote:I thought the question of "stealth in space" had been settled decades ago. There is none.

(Of course, space opera natural laws behave differently so we always have that retreat.)

That said, this was at TL8 if it happened recently, not TL7, but that's a minor point.
Settling questions like stealth is always funny in a sci-fi based game because many of the activities are already violating, or stretching, our understanding of science. Though I find the funnies that "that cannot be done by the laws of science!" statements... which then later get disproven by... wait for it... science! Used to be science said you couldn't fly, but they did. Our understanding of the physical world is far greater than it used to be, but considering we came up with dark matter to explain the weight of the cosmos, and then a decade later Voyager led us to learn that the space between the stars has far more hydrogen in it than we thought. You get the drift, eh?

Who is to say in the future we won't figure out how to convert heat directly to energy which then can be beamed away from the craft via microwaves to just dissipate, thus fixing the thermal issue. If we can have fusion power (which we cannot duplicate), and jump drives (which sidesteps physics), anagathics (an impossibility under current tech), or man-portable fusion generators (whoopsie, another impossibility), why not stealth in space?

As far as the TL7/8 question, some of that gear in operation with the Deep Space Tracking Network can trace it's lineage to TL7, even though overall we might be at TL8. So that's more of a squishy point of view.
Rikki Tikki Traveller wrote:He didn't say "communicated with Voyager" he said "DETECTED Voyager".
We can't detect Voyager at that distance. We are able to listen for it (on frequencies that makes it easier to listen to), but it's too small and too cold to pick up on any detection gear we have currently. We know more or less where it is because we know it's course and velocity (and because it also updates us on it's position). It's not trying to hide.
Rikki Tikki Traveller wrote:Take out all the rotational compensation from a ground-based unit and it becomes a lot easier. AGREED, Voyager is trying to be detected, but a normal civilian transponder is also going to be trying to be detected. Turning off your transponder automatically means you are a pirate or smuggler...
It's not hard at all to compensate for planetary rotation. They did that a long time ago by building multiple tracking locations around the globe. Then again the Voyager spacecraft aren't on system's eliptical plane either. If you wanted to sneak up on a planet you could emerge on the far side of the sun, let gravity pull you in, then just use your drives to slingshot around and turn them off again. Neutrino detectors would fail to "see" you because of the sun's interference, the sun's heat would allow you to hide your ship's heat in the mix far better than if you were coming in from deep space, and with a slingshot maneuver you could be travelling at a good clip without having to resort to your drives. Most arguments about hitting a planet always assume the invading fleet is coming in from deep space when that's not required. Coming in from the sun provides you with a lot of options (though you are also stuck in the system while you are in the sun's jump shadow, so hopefully you have fuel to jump out again).

However, if a ship could go "radio silent" it would only have to worry about the heat signature and the neutrino signature etc. which are harder to detect at TL-7 and probably still hard at higher TL's.
Rikki Tikki Traveller wrote:NOW, my counter-argument...

How many ships/probes are going to be local space around a typical TL-7 world within an interstellar setting. If present-day Earth was contacted by the Vilani (you they are right there at Barnard's Star right?) I would suspect dozens of ships at a time would be somewhere inbound or outbound. So there would be a lot more 'noise' at those unique frequencies of energy put out by spaceships and their communicators. By TL-9, near-space is very busy and it might be quite likely that a ship could hide in the background noise of a busy star system. Think of people whispering in a crowded dining room. COULD they be detected, yes, but it will be difficult and there will be a lot of interference from other conversations - ASSUMING you can't use a directional microphone (since you don't know exactly where they are in the room...)

STILL - I think it makes for an interesting idea. Most RPGs assume it is pretty hard to detect a ship in interplanetary space, but actually, it is likely quite easy - doesn't mean you know anything about them other than "they are over there". Also, detecting them like this doesn't give you distance, only direction until you can triangulate or have another means of determining their signal strength, you can't figure out how far away they are.
Yep. A busy star system is going to have a lot of traffic and such. Discrimination of friend/foe will be harder, especially at the distances you need to consider. Flight plans can help with some of it, but still, you can hide in the open and until they can get close enough to hit you with lidar or radar you are just Freetrader Beowulf, stooging around the system. Until your piratical actions prove otherwise. :mrgreen:

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