Scientific Progress Goes *PING*!

Last night at Apache Point they got their first return from the moon! When the laser leaves the observatory, it's 3.5 meters in diameter. When it hits the moon, it's 2 kilometers (about 1.25 miles) wide, no idea how big it is when it hits the observatory again, I'll have to ask the scientist when I see him again. They're trying to hit a reflector (there are four) that's probably less than 2 meters in diameter, so it's no easy task.

And they've succeeded! In fact, they hit the Apollo 11 reflector, which is the smallest of the four!

Broadly speaking, I guess this is the second stage of the project. The first (after design) was getting it hooked up to the telescope and squirting the laser out of it. Hitting the moon wasn't too difficult, and now they're getting a return. The remaining step is to make sense of the data so they can calculate the distance to the moon.

Timing is a tricky thing here. The laser pulses 100 times a second, to the naked eye it is a continuous stream (perty green light, ma!). The pulses have to be timed so that a return signal hits the detector when the laser isn't lasing, so you've got to be really tight on timing.

Pretty cool stuff.

(The actual Calvin & Hobbes title is 'Scientific Progress Goes *BOINK*, I thought *PING* was a good substitution.)