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