July 20, 1969

Astronaut Michael Collins aboard Columbia inspected Eagle prior to its landing on the lunar surface. (Image source: NASA)

It was time. On July 20, Armstrong and Aldrin entered the Lunar Module (LM), making their final checks before undocking Eagle and separating from Columbia. On board the Command Module, astronaut Michael Collins made a visual check of Eagle and gave the go ahead for a landing.

While the LM was behind the moon on its 13th orbit, its descent engine fired for 30 seconds to begin its descent orbit insertion. On a trajectory that was virtually identical to that flown during the landing dress rehearsal by Apollo 10, Eagle’s new orbit was 9 by 67 miles. After Columbia and Eagle had reappeared from behind the moon, and when the LM was about 300 miles from its landing target, the descent engine fired for 756.3 seconds. After 8 minutes, the LM was at about 26,000 feet above the surface and about five miles from the landing site.

The descent engine continued to provide braking thrust as the LM neared the lunar surface. As Eagle neared the surface, Armstrong took manual control. The powered descent that ran 40 seconds longer than preflight planning due to Armstrong’s deft maneuvering of the LM to avoid a crater during the final phase of landing. The Eagle finally set down in the Sea of Tranquility at Site 2, about four miles downrange from the predicted touchdown point and almost one-and-a-half minutes earlier than scheduled.

“Tranquility Base here, the Eagle has landed!”