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Could we read a newspaper from a satellite image?

  1. Jul 16, 2014 #1
    If the satellites are spread out as a big baseline telescope? Or there are other problems that even that method cant solve when watching the ground?
  2. jcsd
  3. Jul 16, 2014 #2
    They would have to be spread out across at least two orbits, otherwise you would have great resolution along one axis (say North-South) and very poor resolution in the other.

    Ground-based telescopes also use adaptive optics to compensate for atmospheric influence. Those problems are worse when looking up than down, but you might want to have your paper delivered to some tranquil mountain top.

    There is nothing about the physics that could stop this from happening. On the other hand, getting that many telescopes into orbit would break most peoples budget.
  4. Jul 16, 2014 #3
    We'll place the satellites into 180KM orbits - but looking down at an angle at object 200Km away.
    With 0.5mm resolution, we should be able to read newsprint.
    For the purpose of our calculations, we'll use 550nm light.

    So we need 0.5mm/200Km radians resolution. α = 2.5 10^-9 radians
    Our aperture needs to be D = 1.22 L / sin(a) = 1.22 (550nm) sin(2.5 10^-9)
    D = (1.22 550 10^-9 / 2.5 10^-9) M = 270M.

    Call it 500M and make it a single satellite with a few dozen telescopes.

    So what's you budget?
  5. Jul 16, 2014 #4


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    There's a catch here. We can't measure the electric field of visible light since it oscillates too quickly for electronics to respond. In order to get an image with multiple telescopes we need to combine the signal somehow. With radio telescopes we can directly measure the electric field of the signal, store it, and then combine it with the signal from other telescopes later on. But with visible light we have to physically combine the signals before detection. This requires an extremely stable and accurate setup with a path from each telescope to the detector. This is difficult to do here on Earth, and would be nearly impossible for large distances in space at this time.
  6. Jul 16, 2014 #5


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    Years ago .... in the late 1990's
    there was a TV program on spy satellites that I watched. The images that were allowed to be released has no problem reading the headlines on a newspaper.
    For secrecy reasons we were not told just how much more detail could actually be seen by the telephoto cameras on the satellite(s)

    I suspect you would be quite shocked at the high resolution capabilities of these cameras on spy sats.

  7. Jul 16, 2014 #6


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    A newspaper headline when viewed from orbit is on the order of 50-100 milliarcseconds in size. This is barely within the resolution threshold of the Hubble Space Telescope for point-sources, so I'm a bit skeptical about the resolution of a spy satellite. It'd need to have a mirror substantially larger than 2.4 meters to get a clear picture of a newspaper. Or fly a lot lower than the 100 miles I used for my calculations.
  8. Jul 16, 2014 #7


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    Illegally released KH-11 'early block' product images from the 80s:
    Full resolution product could see man sized objects easily.
    A current KH-11 block bird: http://www.heavens-above.com/orbit.aspx?satid=37348

    We could see the paper in a persons hands, could we read it? It seems unlikely.
  9. Jul 16, 2014 #8


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    I doubt we could read a newspaper from space, but, see little practical use for such resolution. For national security purposes, it is generally enough to identify the number and types of military assets is a given area. The KH-7 class spy satellites are reputed to have a resolution down to about 5 cm. Not enough the read a license plate, but, enough to tell if one is present. With modern folded mirror designs, 6-8 meter mirrors can be launched in a single payload. It appears probable the US military has already launched one or more such instruments for their own purposes.
  10. Jul 17, 2014 #9
    Well i saw a film about the elimination of Osama, they claimed, that based on the satellite images they werent 100% sure (of course if one has a double, or more doubles it is really hard even with ground based recon), so i wondered, what scale of resolution could we reach realistically?
  11. Jul 17, 2014 #10
    I believe another way to obtain higher resolution is by taking multiple images from slightly different perspectives of vantage points and then process them heavily and obtain a single higher resolution image...


    A coworker used to work a classified satellite program for an aerospace company and when I was talking about how "fake" shows like CSI are - the way they "enhance" a still image to unbelievable clarity, he agreed on a single frame that there is only so much that can be done, but said there are ways to use multiple images to get unbelievable results.
  12. Jul 17, 2014 #11
    Here's an interesting visual look at what it would mean to be able to read newspapers from a Satellite. It's kind of old. Not sure what new tech we have floating out there.


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