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posted by takyon on Thursday April 09 2020, @06:02PM   Printer-friendly
from the money-hole dept.

NASA Reveals Wild Project For Turning a Moon Crater Into a Radio Telescope

NASA just gave out a new round of grants for its favourite up and coming innovative space projects – one of which is a plan to fit a 1 kilometre (3,281 foot) radio telescope inside a crater on the far side of the Moon.

The Lunar Crater Radio Telescope (LCRT) would be able to measure wavelengths and frequencies that can't be detected from Earth, working unobstructed by the ionosphere or the various other bits of radio noise surrounding our planet.

Should the plans for the LCRT become a reality – and the new grant money could get it closer to that – it would be the largest filled-aperture radio telescope in the Solar System.

Lunar Crater Radio Telescope (LCRT) on the Far-Side of the Moon

-- submitted from IRC


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  • (Score: 1) by khallow on Thursday April 09 2020, @06:50PM (5 children)

    by khallow (3766) Subscriber Badge on Thursday April 09 2020, @06:50PM (#980640) Journal
    They're pretty close to parabolic. You don't need a perfect shape, but you do need a shape good enough that you don't have to build a bunch of skyscrapers to support the ends of your telescope.
  • (Score: 2) by edIII on Thursday April 09 2020, @07:52PM (4 children)

    by edIII (791) on Thursday April 09 2020, @07:52PM (#980653)

    Is it as big of a deal to build skyscrapers on the moon though? The lower gravity certainly affects the engineering requirements. I'm sure this all assumes that we're building things out of regolith again, because getting the materials up there, crater or not, is the bigger issue.

    --
    Technically, lunchtime is at any moment. It's just a wave function.
    • (Score: 5, Informative) by khallow on Thursday April 09 2020, @09:03PM (1 child)

      by khallow (3766) Subscriber Badge on Thursday April 09 2020, @09:03PM (#980667) Journal
      Well, certainly not as bad as on Earth since the weight would be one sixth for the same mass and the mass of the radio antenna would probably be as low as possible on top of that. It still would be an extensive structure that could be greatly reduced or even avoided with a crater.

      Starting with the ground in a near-parabolic shape means you have much lower construction effort and resources required. The radio antenna itself can be pretty negligible in mass. For example, a grid of wires would be sufficient for a reflection surface (particularly, if they're spaced closer than the wavelength of the radio waves. And they sag naturally to near parabolic shape (caternary [wikipedia.org] shape) and perhaps could be tensioned to be even closer in shape to a parabola (though that might add to the structural requirements).

      This can also be abated by making the focal point higher. It's basically an inverse proportional relationship between the focal length (which is the altitude at which the radio waves focus) and the height of the dish at the edge. When both are equal length, a parabolic dish will be four times that length in diameter - so for a 1km dish, focal length and edges would be 250 m high. For edges that are 100 m higher than center, the focal length would be 625 m. Another issue is that the longer you make the focal length, proportionally the more play you have to put in the detector to look at things that are off axis (or the bigger the detector, if you're trying to get a large field of view). So a sensor on top of a 625 m tower would have to deviate sideways by 2.5 m to get the same image as a 1 m deviation on a 250 m tower.

      In summary, there's a lot of stuff to consider and finding a usable crater isn't going to be enough on its own to minimize structural requirements.
      • (Score: 2) by edIII on Friday April 10 2020, @12:05AM

        by edIII (791) on Friday April 10 2020, @12:05AM (#980691)

        Thanks for explaining all of that.

        --
        Technically, lunchtime is at any moment. It's just a wave function.
    • (Score: 2, Interesting) by Myfyr on Thursday April 09 2020, @10:43PM

      by Myfyr (3654) on Thursday April 09 2020, @10:43PM (#980685)

      In this case the telescope is a wire mesh, so no building required . Using a bunch of rovers to deploy, and then anchor and suspend, a pre-built wire mesh from the edges of a crater is orders of magnitude easier than erecting anything. Which makes this look quite interesting, since it might actually happen in the somewhat near future. Fingers crossed.

    • (Score: 2) by deimtee on Thursday April 09 2020, @11:53PM

      by deimtee (3272) on Thursday April 09 2020, @11:53PM (#980690) Journal

      It also doesn't have to stand up to wind. You could build it out of tinfoil squares stuck on the top of something like fibreglass fishing poles.

      --
      If you cough while drinking cheap red wine it really cleans out your sinuses.