NASA Fires Twin Lasers at the Moon

[JohnD]

SPACE.com -- Snapshot: NASA Fires Twin Lasers at the Moon

 

[Flaminpyro]

Well darn I was hoping they would tell how powerfull there lasers are to be able to reach the moon and back.

 

[qumefox]

I'm not sure about these, but I remember seeing something in the past about the dpss they use to measure the distance to the moon with the cornercube left from the apollo missions as being ~20W.

 

[ped]

Aye, they didnt get THEM from focalprice! :crackup:

 

[pullbangdead]

The "wattage" isn't that applicable with these experiments.

They want time measurements, so they want pulses as short as possible, but a lot of power in that short pulse since they get VERY few photons back. The APOLLO measurement set-up generally uses a 90 picosecond pulse with a pulse energy of ~115 mJ. So during the pulse, that's ~1.3 gigawatts, but it only does that 20 times per second, so that's a time-average of about 2.3 Watts.

And their optics matter: they're using a 3.5 meter telescope as a beam expander to get lower divergence.

 

[ped]

The "wattage" isn't that applicable with these experiments.

They want time measurements, so they want pulses as short as possible, but a lot of power in that short pulse since they get VERY few photons back. The APOLLO measurement set-up generally uses a 90 picosecond pulse with a pule energy of ~115 mJ. So during the pulse, that's ~1.3 gigawatts, but it only does that 20 times per second, so that's a time-average of about 2.3 Watts.

And their optics matter: they're using a 3.5 meter telescope as a beam expander to get lower divergence.

*coughs* yeah what he said^^

Now its as clear as pea soup

:takeit:

 

[BShanahan14rulz]

I heard that they use laser light because it's monochromatic, so they can build a very sensitive photon detector and if they see a jump in just that wavelength. They can sense if just a few extra photons reflect back.