Retroreflectors on the moon are completely useless. They don't actually work at all.
1) It is mathematical fact that setting up a mirrored corner can return the light from whence it came. But this would require engineering the mirrors to be perfectly flat, and perfectly right-angles. There is very little tolerance for error, because you're reflecting a signal 380,000 kilometers across empty space. Even the smallest angular deviation throws your signal completely off
2) It takes light around 2.6 seconds to reach the moon and back. During that time, the earth turns. If you do the math, it will displace the return signal by 1.2 kilometers. Not to mention the earth and moon's mutual rotation displaces it by another 10 meters.
3) The retroreflectors are really small. We know that even a columnar laser spreads out with 1/r^2 of the distance. Therefore this signal reaching the moon has a large radius, and is bouncing off much of the reflective soil around the entire area, kind of like sonar. Considering it's possible to measure the return-signal, which should be displaced by over 1,200 meters, that means the signal probably spreads out a minimum of 600 meters when it hits the moon. 600 meters square is 360,000 square meters. Thus if the soil on the moon returns just 1/360,000th's of the signal as the retroreflector, then it has outperformed the reflector, rendering the reflector totally pointless.
1) It is mathematical fact that setting up a mirrored corner can return the light from whence it came. But this would require engineering the mirrors to be perfectly flat, and perfectly right-angles. There is very little tolerance for error, because you're reflecting a signal 380,000 kilometers across empty space. Even the smallest angular deviation throws your signal completely off
2) It takes light around 2.6 seconds to reach the moon and back. During that time, the earth turns. If you do the math, it will displace the return signal by 1.2 kilometers. Not to mention the earth and moon's mutual rotation displaces it by another 10 meters.
3) The retroreflectors are really small. We know that even a columnar laser spreads out with 1/r^2 of the distance. Therefore this signal reaching the moon has a large radius, and is bouncing off much of the reflective soil around the entire area, kind of like sonar. Considering it's possible to measure the return-signal, which should be displaced by over 1,200 meters, that means the signal probably spreads out a minimum of 600 meters when it hits the moon. 600 meters square is 360,000 square meters. Thus if the soil on the moon returns just 1/360,000th's of the signal as the retroreflector, then it has outperformed the reflector, rendering the reflector totally pointless.
