This kind of thing makes me giddy:
...since launching the Lunar Reconnaissance Orbiter, they've [the Goddard Space Center in Maryland] been firing a laser across 250,000 miles of space, hitting the minivan-sized LRO as it orbits the moon at nearly 3,600 miles per hour. It's no lucky shot either; they do it 28 times per second.
But perhaps even more impressive is the accuracy of the information the laser gathers. The Goddard laser is the first laser ranging effort to extend beyond low earth orbit, and it is able to measure the range of the LRO to within four inches. The microwave stations that are also tracking the LRO, by comparison, have a margin of error of about 65 feet. The accuracy provided by the lasers in turn allows researchers to know exactly where the LRO is in space, a critical component for creating accurate maps of the moon's surface.
The fundamentals behind the laser ranging are actually quite simple. A telescope on the ground at Goddard fires one-way laser pulses across space to the LRO. When the laser gets there, the LRO makes a record of each contact and sends it back to earth via its radio telemetry link. After that, good old-fashioned arithmetic is used to calculate the distance to LRO based on how long it takes the pulse to reach it.
Using this to map the lunar surface sounds like a waste of time--unless you care about science and innovation. This may not seem like all that, but it really is a good thing that we are seeing some success in our space program. Scientific innovation, which can lead to new products for us here on Earth, should be encouraged.