Transcript for Apollo 11 anniversary: Revisiting the moment Americans landed on the moon
We turn to the moon landing. Tomorrow marks the 50th anniversary of Apollo 11 touching down and a new documentary from national geographic explores how we got there. ABC's David Kerley has more from one of my very favorite places in all of Washington, the national air and space museum, hey, David. Reporter: One of my favorite spaces as well, Cecilia. Where do you get to see this? This is an actual lunar lander. Never flew in space. A test model but look at that. At this hour 50 years ago it was preparing to go into orbit for that remarkable landing. Program alarm. Reporter: Drama 50 years ago, national geographic's Apollo migs to the moon mixes the conversations from Houston and the astronauts trying to land on the moon as a computer alert nearly leads to an abort. Give us a reading on the 1202 program alarm. Houston, you're a go for landing. Reporter: But then Armstrong takes manual flight control to avoid Boulders in the landing zone burning more precious fuel. Listen to his concern. Okay, how's that? Wait a minute. Looks like a good area. Reporter: The warnings, 60 seconds of fuel, 30 seconds then with less than 20 seconds of fuel. Houston, tranquility base here. The eagle has landed. Reporter: Neil Armstrong who took that one small step for man -- That's one giant leap for mankind. Reporter: -- Was followed by one of the most anxious moments in the mission for astronaut Mike Collins in the command module orbiting the moon. With only one rocket on the lunar lander he was worried it might not work leaving Armstrong and aldrin marooned. You talked about being a marked man if you had to come back alone. That would not have been a Reporter: But the astronaut who seemed to be the happiest on the crew was not disappointed. As all three heroes splashed down safely. 50 year, that is the legacy of Apollo 11? So many things that could go wrong and yet nothing did. That to me is what I remember and most amazing thing about it. Everything worked. Reporter: Everything did work and I want to give you a close-up look at this lunar landing. You don't get to see this often. The ladder they came down up top they called the porch and that little scare is the hatch they opened up and had to back out on their hands and knees on to the surface of the moon. Here at the museum they're putting out the foot prints they actually walked on the moon around the lunar lander. That anniversary of the landing tomorrow night, I highly recommend that nationalgeo documentary if you want to learn more about that. So cool. You got a good assignment. Thank you "Apollo migs to the moon" is available Meteorologist, Amy freeze.
This transcript has been automatically generated and may not be 100% accurate.