31 October 2011

Lasers, Lunar Landings, and LRO

Posted by Ryan Anderson

Here’s another guest post from Seth Humphries about the amazing achievement that was the Apollo program, and the LRO photos of some of the landing sites.

As a grad student, I spent a lot of time in hay fields with lasers.  Using a tunable laser, I built the Differential Absorption Measurement (DAM) Instrument to measure concentrations of carbon dioxide in the air above sequestration sites, oil wells injected with CO2. During this time, sometime in 2007, I bumped into a friend and he introduced me to an acquaintance of his, a young man about 20. The three of us talked for quite a while and the conversation turned to my work. The young man was very interested in my work. I described how the tunable laser worked, how we were able to measure carbon dioxide and why it mattered. He was genuinely interested lasers and asked about other uses. I explained that laser can be used for cutting steel, measuring how fast cars are traveling, and as guide stars for observatories. I mentioned that scientists are able to accurately measure the distance to the moon by bouncing the lasers off or reflector arrays placed there by the Apollo astronauts.

The Apollo 11 laser reflector deployed on the surface.

As I talked about the astronauts on the moon, I watched this guy’s face change. He thought for a minute and asked something like: You think we landed on the moon? Without knowing what I was doing I had stumbled onto one of the strongest pieces of evidences proving that humans have walked on the moon.  To be fair, I don’t think this young man was into the moon landing hoax conspiracies, I think his question was sincere, having never heard of the Apollo missions nor astronauts being sent to the moon. He had thought lasers were cool, now he was in awe that someone had walked on the moon.

Since that conversation I have become more interested in the Apollo missions. I even have panoramas from the Apollo 17, Apollo15 and Apollo 12 missions in rotation as my desktop background. As I have learned more about the Apollo missions I am continually in awe at some of the accomplishments. For example, just the launch pad required design to withstand the intense heat from the burning rocket fuel. Here is a slow-motion video clip with commentary from the launch of Apollo 11. The clip is about 8 minutes long but worth the view.

Another example of the engineering marvels of the Apollo missions is that the Apollo12 lunar capsule landed within 180 meters (600 ft) of its targeted site, the Surveyor III robot. That is like hitting a bullseye with a bottle rocket from a 100 yards away.  Oh, and they managed that after being hit by lightning shortly after launch. Twice. And remember that most “compact” computers of the day were the size of large desks. The Apollo computers were unique with hard-coded rope like memory that had to be woven into the computer. They called it LOL memory, not for laugh-out-loud but for the little-old-ladies who spent hours weaving it all together. They are probably still functional even after sitting on the moon for so long. After touching down next to the Surveyor III landing site, Apollo 12 brought back a camera and other pieces of Surveyor. The camera is now on display at the National Air and Space Museum.

Recently, I’ve been very interested in the high-resolution images being returned by the Lunar Reconnaissance Orbiter (LRO). LRO is in a low-altitude, polar orbit making accurate altitude measurements of the moon using laser radar, taking high resolution pictures and making other measurements in order to create detailed 3D maps of the lunar surface. The maps are intended to be useful to the next set of lunar explorers. Most of the returned images are only interesting to planetary geologists but there are some images that have a certain coolness factor that the rest of us can appreciate. My favorite so far is this image of the Apollo 17 landing site.

You can clearly see the tracks left by the Lunar Reconnaissance vehicle (LRV) driven Eugene Cernan and Harrison Schmitt. You can see where they went, and even the remnants of the landing module and some of their equipment.  Since there is no wind on the moon, their footprints and tracks will remain intact until we can walk over them, retracing the steps they took so long ago.


Seth Humphries is the Product Development Scientist at Apogee
Instruments. Previously he was a Post-Doc at Los Alamos National Lab
working on a laser based carbon sequestion monitoring system, ChemCam
validation experiments, etc. He has a long history of involvement in
space-based research and continues to hope to become an astronaut.