[HN Gopher] Using the Moon as an Echo [video]
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       Using the Moon as an Echo [video]
        
       Author : tws
       Score  : 36 points
       Date   : 2024-08-08 06:47 UTC (1 days ago)
        
 (HTM) web link (www.youtube.com)
 (TXT) w3m dump (www.youtube.com)
        
       | Terr_ wrote:
       | > radio telescope
       | 
       | From the title I thought it might be about using lasers against
       | lunar retroreflectors, passive arrangements of precise mirrors
       | that (usually) reflect light back to its source.
       | 
       | https://en.wikipedia.org/wiki/List_of_retroreflectors_on_the...
        
       | philiplu wrote:
       | I was explaining ham radio to my kids last night (something
       | neither teenager had ever heard of), and ran across
       | https://en.wikipedia.org/wiki/Earth-Moon-Earth_communication.
        
       | dredmorbius wrote:
       | My understanding is that before the development of observation
       | satellites in the 1960s, radio echos from the Moon were used to
       | detect nuclear explosions (testing or military use) from the far
       | side of the Earth. Even if direct observations were not possible
       | / were limited, so long as the Moon was observable both over the
       | test site and a US-friendly (not necessarily US-based) receiving
       | station, such signals could be detected.
       | 
       |  _The Arecibo's site origins trace back to the 1950s, when
       | Cornell University proposed its construction to the Department of
       | Defense's Advanced Research Projects Agency (ARPA), which is
       | today known as the Defense Advanced Research Projects Agency
       | (DARPA). A desire to better understand the composition of the
       | ionosphere and how it might impact objects passing through,
       | including ballistic missile reentry vehicles carrying nuclear
       | warheads, was a key reason for its construction. At the time,
       | ARPA was in charge of a broad ballistic missile defense program
       | known as Project Defender. It was believed that nuclear warheads
       | would produce a distinct signature when reentering the
       | atmosphere, making it possible to distinguish them from decoys,
       | so long as that signature could be quickly identified and
       | categorized. The plan was to use the Arecibo Telescope to help
       | gather general, but still valuable information about the
       | ionosphere in support of this effort._
       | 
       | <https://www.twz.com/37898/collapsed-arecibo-radio-telescope-...>
        
       | xxdiamondxx wrote:
       | Oh hey I have that same ham radio! Kenwood TS-2000. I guess I
       | just need a giant radio telescope...
        
         | _whiteCaps_ wrote:
         | A cross polarized Yagi can do EME bounce as well. You need an
         | az/el rotator to track the moon though.
        
       | motohagiography wrote:
       | What a useful tool that saves me time. My weekend project this
       | week was literally just writing a canon for modular synth that
       | used a moon bounce for the second voice. I figured I could
       | compose it with a delay set to 2.7sec, and then play with the
       | clock via Maths for a performance- but their plugin sounds like
       | this is more complex and interesting.
       | 
       | Lunar bounce canons could become an entire form arising from that
       | 2.7sec constraint.
        
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       (page generated 2024-08-09 23:00 UTC)