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How is such thing able to communicate back with earth? Doesn't it require a lot of energy to create signal that we will be able to receive on earth (or satelite

by comboy 11y ago

How is such thing able to communicate back with earth? Doesn't it require a lot of energy to create signal that we will be able to receive on earth (or satelite)?

rm_-rf_slash 11y ago
Not a scientist but I first read this on The Economist and they summed it up pretty well: "At its destination it would beam back pictures of the star’s planets with its on-board laser. No current observatory could possibly pick up such a signal—but the kilometre-wide launch array should be able to. The optical systems used to meld the output of the lasers could be used in reverse as a vast and sensitive telescope." http://www.economist.com/news/science-and-technology/21696876-interstellar-travel-means-thinking-both-very-big-and-very-small-new-plan http://www.economist.com/news/science-and-technology/2169687...
- slg 11y ago
  This might be a stupid question, but if we have the technology to see a blinking light the size of a postage stamp trillions of miles away, why would we need to send a probe with a camera all the way out there in the first place?
  - Carrok 11y ago
    Because while all we can see is the blinking light, the probe can see the things close to it far more clearly. As the above quote says the probe will "beam back pictures of the star’s planets." We can receive these pictures through the data received from that blinking light, but we can't see the planets in question. Now we can.
    - slg 11y ago
      But why would we be unable to see the star's planets if we are able to see a probe that small?
      - dysfunction 11y ago
        We wouldn't be able to see the probe itself, rather we'd see its laser. The planet outputs (or reflects) vastly more total light than the laser, but the laser is pointed directly at the receiver and can output more light in that specific direction than the planet does. Plus, to get interesting data about the planet we need to get quite a lot of light from it, whereas we can get data from the laser over time by pulsing it so long as we can get any light from it at all.
        slg 11y ago
        >The planet outputs (or reflects) vastly more total light than the laser, but the laser is pointed directly at the receiver and can output more light in that specific direction than the planet does. So then the problem is that you need a laser than can hit a 1 km^2 target from 40 trillion km away?
        drdrey 11y ago
        No, the laser would point in the general direction of the sun and as long as Earth is within the cone it has the potential to detect the signal. The laser just happens to focus all of its energy in one narrow cone as opposed to all directions.
      - cb18 11y ago
        'Seeing' the probe is like being connected to the internet. Your friend in Japan can take a picture of an apple and email it to you in the US. Your friend's camera is like the camera on the probe. You can't see the apple from where you are, but your computer can 'see' the internet. Your friend uses the internet to send you a digital code that your computer turns into a picture of an apple. The optical systems used to meld the output of the lasers could be used in reverse as a vast and sensitive telescope. But why would we be unable to see the star's planets if we are able to see a probe that small? The laser receiver might be able to see the planets in question, but a probe with an interstellar worthy camera in the direct vicinity of the planets would obviously be able to capture a much higher resolution image.
      - 11y ago
  - jperras 11y ago
    To answer that question, you need to know a little bit about diffraction-limited systems in optics and the Rayleigh criterion. Essentially, point-like sources (the laser emitter array and the target can be considered point sources when on the scale of lightyears) separated by an angle smaller than the angular resolution of the device in question cannot be resolved.
- david-given 11y ago
  I'd be kinda hesitant about relying on a ground-based receiving station. How stupid would you feel if after 40 years flight, you missed the return signal because your receiving station happened to be on the wrong side of the Earth?
lunchTime42 11y ago
Same way it got there? Laser focused on earth? Needs good aiming though.
- Cerium 11y ago
  Modulated retro-reflector. We pulse firing a lower power laser at it and it reconfigured the mirror to modulate the returned signal. Essentially an interstellar DLP projector.

by comboy 11y ago

How is such thing able to communicate back with earth? Doesn't it require a lot of energy to create signal that we will be able to receive on earth (or satelite)?

rm_-rf_slash 11y ago

Not a scientist but I first read this on The Economist and they summed it up pretty well: "At its destination it would beam back pictures of the star’s planets with its on-board laser. No current observatory could possibly pick up such a signal—but the kilometre-wide launch array should be able to. The optical systems used to meld the output of the lasers could be used in reverse as a vast and sensitive telescope." http://www.economist.com/news/science-and-technology/21696876-interstellar-travel-means-thinking-both-very-big-and-very-small-new-plan http://www.economist.com/news/science-and-technology/2169687...

slg 11y ago
This might be a stupid question, but if we have the technology to see a blinking light the size of a postage stamp trillions of miles away, why would we need to send a probe with a camera all the way out there in the first place?
- Carrok 11y ago
  Because while all we can see is the blinking light, the probe can see the things close to it far more clearly. As the above quote says the probe will "beam back pictures of the star’s planets." We can receive these pictures through the data received from that blinking light, but we can't see the planets in question. Now we can.
  - slg 11y ago
    But why would we be unable to see the star's planets if we are able to see a probe that small?
    - dysfunction 11y ago
      We wouldn't be able to see the probe itself, rather we'd see its laser. The planet outputs (or reflects) vastly more total light than the laser, but the laser is pointed directly at the receiver and can output more light in that specific direction than the planet does. Plus, to get interesting data about the planet we need to get quite a lot of light from it, whereas we can get data from the laser over time by pulsing it so long as we can get any light from it at all.
      - slg 11y ago
        >The planet outputs (or reflects) vastly more total light than the laser, but the laser is pointed directly at the receiver and can output more light in that specific direction than the planet does. So then the problem is that you need a laser than can hit a 1 km^2 target from 40 trillion km away?
        drdrey 11y ago
        No, the laser would point in the general direction of the sun and as long as Earth is within the cone it has the potential to detect the signal. The laser just happens to focus all of its energy in one narrow cone as opposed to all directions.
    - cb18 11y ago
      'Seeing' the probe is like being connected to the internet. Your friend in Japan can take a picture of an apple and email it to you in the US. Your friend's camera is like the camera on the probe. You can't see the apple from where you are, but your computer can 'see' the internet. Your friend uses the internet to send you a digital code that your computer turns into a picture of an apple. The optical systems used to meld the output of the lasers could be used in reverse as a vast and sensitive telescope. But why would we be unable to see the star's planets if we are able to see a probe that small? The laser receiver might be able to see the planets in question, but a probe with an interstellar worthy camera in the direct vicinity of the planets would obviously be able to capture a much higher resolution image.
    - 11y ago
- jperras 11y ago
  To answer that question, you need to know a little bit about diffraction-limited systems in optics and the Rayleigh criterion. Essentially, point-like sources (the laser emitter array and the target can be considered point sources when on the scale of lightyears) separated by an angle smaller than the angular resolution of the device in question cannot be resolved.
david-given 11y ago
I'd be kinda hesitant about relying on a ground-based receiving station. How stupid would you feel if after 40 years flight, you missed the return signal because your receiving station happened to be on the wrong side of the Earth?

lunchTime42 11y ago

Same way it got there? Laser focused on earth? Needs good aiming though.

Cerium 11y ago
Modulated retro-reflector. We pulse firing a lower power laser at it and it reconfigured the mirror to modulate the returned signal. Essentially an interstellar DLP projector.