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Tuesday, August 26, 2008

Shooting Lasers at the Moon

Ron Sparks, AG5RS, sent us this very cool picture. My kids take great delight in shooting those tiny red laser pointers out the window, and as described in SolderSmoke we actually built a simple laser communications system. But so far we haven't achieved the kind of "beam shooting into the sky" effect pictured here.

Here are Ron's comments.:

"It was interesting for you to mention the lunar laser reflector. It had a very special impact on my life. You see, I grew up in Texas at about the midpoint of the 600 mile line between NASA Clear Lake and the McDonald Observatory in the Davis mountains and was in High School when Neil Armstrong walked on the moon. I had the pleasure to visit both NASA and McDonald at that time and had direct contact with some of the people responsible. I have actually put my hands on the controls for the laser in the attached photo. More importantly, the control box was opened up for me so I could see all the gizmos inside."

Check out the website: The Lunar and Planetary Institute

The website has some interesting info on the width of the laser beam when it reaches the moon, and how they use the data to measure the distance. Sounds vaguely QRSS-ish:

"Laser beams are used because they remain tightly focused for large distances. Nevertheless, there is enough dispersion of the beam that it is about 7 kilometers in diameter when it reaches the Moon and 20 kilometers in diameter when it returns to Earth. Because of this very weak signal, observations are made for several hours at a time. By averaging the signal for this period, the distance to the Moon can be measured to an accuracy of about 3 centimeters (the average distance from Earth to the Moon is about 385,000 kilometers). "

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