QVRedit t1_isse23p wrote
Reply to comment by drnobodyhome in Surprise discovery of radio signals could help track space junk and limit global security risks by marketrent
Actually they use lasers and bounce a ‘light signal’ off of the moon to measure its distance - One of the Apollo missions left a ‘retro-ranging laser reflector’ on the surface of the moon - that is used to reflect the beam back.
The signal coming back is very much weaker than the one sent out - but it’s enough to measure the time delay - and so the distance, which is measured daily. That’s how we know that it varies.
The moon is moving 3.78 cms per year further away from the Earth - it’s due to tidal effects. The Moon is stealing energy from the Earths rotation, so accelerating it very slowly away from the Earth.
drnobodyhome t1_ist2ous wrote
You're correct, seems memory failed me on that one. Been while since I had seen it and misremembered . As to the intent of reply that the broadcast station should have been aware of the concept of using reflected radio waves, the rest of my reply is most certainly correct, and via the same of using precision timing, return strength, triangulation, etc. The details of the distant object can be determined and is not a new thing.
QVRedit t1_istgj9e wrote
Reflected radar waves are definitely used to range asteroids, amoung other techniques
Viewing a single comment thread. View all comments