This Saturday marks the 50th anniversary of the Apollo 11 landing on the moon. In advance of the milestone, NASA has released a truly stunning video that portrays a part of the landing that nobody has seen until now.

It depicts roughly the last three minutes of the voyage to the moon as seen out of mission commander Neil Armstrong's window, when Armstrong had to manually take control of the lander, and steer the Lunar Module away from rocks and debris that covered the intended landing site.

His last-minute evasions meant the spacecraft landed with only enough fuel left for less than another minute of flight -- but they also meant the lander didn't crash on some of the five or 10-foot boulders. 

Too busy to talk.

At the time, Armstrong is so busy flying that he never actually has time to explain what he's doing as it happens. His fellow astronaut Buzz Aldrin can be heard calling out navigational data and staying in touch over the radio with Houston.

Meanwhile, the only camera mounted on the lunar lander was on Aldrin's side of the spacecraft, which meant nobody else was ever able to see what Armstrong saw, and how and why he took over the controls at the last minute.

At least, nobody could see it until now.

Just ahead of the anniversary, the NASA team working on the Lunar Reconnaissance Orbiter, a satellite that has been orbiting the moon for nearly a decade, has created a simulated reconstruction using real images that shows Armstrong's view during the approach to the moon.

This isn't CGI; it's actual photography, as the team explained in a statement:

"The LROC team reconstructed the last three minutes of the landing trajectory (latitude, longitude, orientation, velocity, altitude) using landmark navigation and altitude call-outs from the voice recording. 

From this trajectory information, and high-resolution LROC NAC images and topography, we simulated what Armstrong saw in those final minutes as he guided the LM down to the surface of the moon." 

What Armstong and Aldrin saw.

There are two versions of the video. This one (link) shows the simulated Armstrong view alone; this one (embedded below) shows the simulated version of what Armstrong saw coupled with the real-life 16 mm, six-frames-per-second film recording of what Aldrin saw from his side.

Over the next few days, we'll have a lot of opportunity to talk about the technological marvels and leadership attributes that made the moon landing mission possible. And we can even debate whether the mission was worth the cost.

But for now, it's impressive just to watch and listen to how Armstrong and Aldrin composed themselves calmly, and reacted quickly, during one of the most stressful, dangerous, and monumental missions of all human history.

"About to turn blue."

Ironically, a NASA history of the Apollo 11 on its website reports Armstrong's maneuvers with just two unexciting sentences:

"During the final approach, the commander noted that the landing point toward which the spacecraft was headed was in the center of a large crater that appeared extremely rugged, with boulders of five to ten feet in diameter and larger.

Consequently, he switched to manual attitude control to translate beyond the rough terrain area."

But if Armstrong hadn't taken control, and the two astronauts hadn't acted as they did during those last few minutes, this week's anniversary might be recalling a very different outcome.

I tend to prefer the real-time transcript, which makes the importance and difficulty a bit more clear:

Armstrong: "Houston, Tranquility Base here. The Eagle has landed."

Houston: "Roger, Tranquility. We copy you on the ground. You've got a bunch of guys about to turn blue. We're breathing again. Thanks a lot."