Apollo 11 experiment that's still going

GoodBoy

[H]ard|Gawd
Joined
Nov 29, 2004
Messages
1,713
The Lunar Laser Ranging Experiment lets NASA precisely measure the distance between Earth and the moon, and the experiment is still ongoing to track the moon’s orbit and variations in its rotation. The experiment allowed the distance between the Earth and the Moon to be measured to centimeter accuracy.

During the attempts to complete the experiment, it became apparent to the U.S. scientists scrutinizing the Sea of Tranquility that someone else on Earth also was firing a laser at the moon and attempting to hit the LURE array, according to Hagerty.

“Those rogue laser shots, it turned out, were from a team of Soviet scientists, who hoped to achieve an end run around the U.S. groups,” he wrote.
Full story: https://spectrum.ieee.org/the-institute/ieee-history/one-apollo-11-experiment-is-still-going-50-years-later
 

GoodBoy

[H]ard|Gawd
Joined
Nov 29, 2004
Messages
1,713
Lol, that crazy kid and his 5+ watt lasers... The experiment was using gigawatt lasers. Bet he would have fun with those.

In fact the divergence likely helps, as hitting a 1 meter wide target, on a moving target that's 238,900 miles away, with a small non-diverging beam, would be impossible by hand. And without the divergence, depending on where you are on earth and where the moon is in the sky, the reflected beam would be elsewhere on the planet, or impossible to detect. But a beam that diverges into a 2km circle on the moon will be easier to find the target. Probably still has to be done with a machine. The beam diverges into ~1.8km at the moon, and the reflected photons diverge even more to about 15km wide square.

Edit: Apparently this is possible to do with about 5 watts of laser power, but it does take precise machinery to aim, and detect the return signal.
 
Last edited:

Jim Kim

2[H]4U
Joined
May 24, 2012
Messages
3,643
Lol, that crazy kid and his 5+ watt lasers... The experiment was using gigawatt lasers. Bet he would have fun with those.

In fact the divergence likely helps, as hitting a 1 meter wide target, on a moving target that's 238,900 miles away, with a small non-diverging beam, would be impossible by hand. And without the divergence, depending on where you are on earth and where the moon is in the sky, the reflected beam would be elsewhere on the planet, or impossible to detect. But a beam that diverges into a 2km circle on the moon will be easier to find the target. Probably still has to be done with a machine. The beam diverges into ~1.8km at the moon, and the reflected photons diverge even more to about 15km wide square.

Edit: Apparently this is possible to do with about 5 watts of laser power, but it does take precise machinery to aim, and detect the return signal.
The return signal is measured in photons.
 
Top