Tranquility Base, Houston,” called Capcom
Ronald E. Evans on July 21, 1969, to awaken Apollo 11 astronauts Neil A.
Armstrong and Edwin E. “Buzz” Aldrin after their night’s sleep on the Moon. Armstrong
responded with a crisp, “Good morning, Houston. Tranquility Base.”
Aldrin went on to describe how he had slept on the floor of
the Lunar Module (LM) Eagle while
Armstrong had slept on the ascent engine cover with a make-shift sling to hold
his legs up. Both slept with their suits, helmets and gloves on, since the
temperature in the cabin was a chilly 61 degrees Fahrenheit. Neither man had
slept too soundly, partly from the excitement of the previous day’s activities,
and partly from the unusual sleeping arrangements. Moreover, the Earth was
shining through a navigation telescope right into Armstrong’s eyes.
Earlier, Evans had awakened Michael Collins, orbiting the
Moon aboard the more spacious Command Module (CM) Columbia, who had enjoyed a more restful night. All three men
prepared for Eagle’s liftoff from the
lunar surface and rendezvous and docking with Columbia. Before departure, Armstrong and Aldrin used the 16-mm
film camera to once more document their landing site through the LM’s windows,
showing that the American flag had shifted position overnight, apparently
settling in the loose lunar soil.
Left: Shortly after
the spacewalk, from Aldrin’s window, showing the flag and the TV camera. Right:
The next morning, also from Aldrin’s window, showing that the flag had changed
position. Image Credits: NASA
As a historical side note, as Armstrong and Aldrin were
preparing for their departure from the Moon, the Soviet
Luna 15 robotic spacecraft, which had launched three days before Apollo 11,
fired its retrorocket after completing 52 lunar orbits. Signals with the craft
were lost four minutes later, and it is believed to have crashed in the Mare
Crisium approximately 500 miles from Tranquility
Base, traveling at an estimated 300 mph.
After ensuring that all switches and circuit breakers were properly
configured (including the one that arms the ascent stage engine that was
accidentally broken by Aldrin’s Portable Life Support System backpack, which had
to be activated using a felt-tip pen), Evans called up, “You’re cleared for
Aldrin responded, “Understand. We’re number one on the
After a 21-hour stay, the LM’s Ascent Propulsion System
(APS) engine fired precisely on time, lifting Eagle’s ascent stage off
the surface of the Moon, using the descent stage as a launch pad.
Aldrin reported, “We're off. Look at that stuff [insulation
from the decent stage] go all over the place. Look at that shadow. Beautiful.”
Armstrong, for the second time during the mission, radioed,
“The Eagle has wings.”
Aldrin had installed the 16-mm film camera in
his window, but didn’t activate it until six seconds after liftoff. They
reported that the ascent stage was giving them a very smooth and quiet ride.
The seven-minute APS burn placed them in a 54-by-11-mile orbit.
Armstrong proclaimed, “The Eagle is back in orbit, having left Tranquility Base.”
Sequence of images taken by Collins in Columbia showing Eagle’s approach for docking. Image Credits: NASA
An hour later, with both Eagle and Columbia behind the Moon, the LM’s Reaction Control System (RCS)
thrusters fired for two minutes to circularize the LM’s orbit to be 58 by 53
miles. Another hour later, a one-minute RCS burn changed Eagle’s orbit so that it was a constant 17 miles below Columbia’s. At this point, the two
spacecraft were 100 miles apart, with Eagle
in the lower orbit catching up to Columbia.
A final burn 30 minutes later put Eagle
on an intercept course with Columbia.
Armstrong then made a short
braking burn, followed by several smaller midcourse maneuvers, to complete the rendezvous.
The astronauts in the two vehicles could now see each others’ spacecraft, and Collins
filmed Eagle’s final approach. As the two spacecraft neared each other, they came around
from the Moon’s far side, and Collins was treated to a view of Eagle back-dropped by the Earth rising
over the lunar horizon. Less than four hours after lifting off from the lunar
surface, and with Armstrong holding Eagle
in position, Collins guided Columbia
in for the docking. The two craft were reunited after spending nearly 28 hours
With the hatches open between the two spacecraft, Armstrong
and Aldrin began to clean up as much of the lunar dust as they could, using part
of the back-contamination prevention procedures, and transferred the lunar rock
boxes, film cassettes, solar wind experiment and other items from Eagle into Columbia. Within two hours they completed all the transfers, closed
the hatches for the final time and jettisoned Eagle, which remained in lunar orbit until crashing on the Moon’s
surface several months later.
Apollo 11 orbited the Moon for another five hours. Then, while
behind the Moon, the CM fired the Service Propulsion System (SPS) engine for
the two-and-a-half-minute Trans Earth Injection (TEI) burn at the end of Columbia’s 30th lunar orbit to send the
At the time of the burn, Columbia
was 20 miles in front of and one mile below Eagle.
As they rounded from behind the Moon, Armstrong called down to Capcom Charles
M. Duke in mission control, “Time to open up the LRL
He was referring to the Lunar
Receiving Laboratory at the Manned Spacecraft Center in Houston, now NASA’s Johnson
Space Center, where the astronauts would be quarantined after their mission and
the Moon rocks first examined.
Duke responded with, “We
got you coming home. It's well stocked.”
After TEI, the astronauts took
their last photographs of the lunar far side and of the Earthrise.
View of the lunar far
side, including the large Tsiolkovski Crater (at top center) and two of the
final Earthrise photos taken by Apollo 11 after TEI. Image Credits: NASA
The astronauts took a series of photographs of the receding
Moon and placed their spacecraft into the Passive Thermal Control, or barbecue
mode, rotating along the spacecraft’s longitudinal axis three times each hour
to evenly distribute temperature extremes.
Director of Flight Crew Operations Donald K. “Deke” Slayton
radioed up to the crew,
“This is the original Capcom. Congratulations
on an outstanding job. You guys have really put on a great show up there. I
think it's about time you powered down and got a little rest, however. You've had a mighty long day here. Hope you're
all going to get a good sleep on the way back. I look forward to seeing you
when you get back here. Don't fraternize with any of those bugs en route,
except for the Hornet.”
Slayton was making a humorous reference to any possible Moon
germs the astronauts may be carrying back with them, which necessitated the
postflight quarantine to prevent back contamination. That would begin as soon
as they arrived aboard the prime recovery ship the USS Hornet after splashdown in the Pacific Ocean.
As the Apollo 11 astronauts prepared for their first sleep
period of the Earthbound journey, mission control finally lost contact with Eagle, still in lunar orbit, as its batteries
could no longer power its navigation system to point its antenna toward Earth.
Apollo 11 astronauts
photograph the receding Moon from (left to right) 1,920 miles; 3,420 miles;
5,380 miles; and 12,030 miles away. Image Credits: NASA
Shortly after the astronauts awoke from a 10-hour rest
period, they passed out of the Moon’s sphere of influence and into Earth’s, and
began accelerating toward their home planet. At a distance of 194,500 miles
from Earth, they conducted an 11-second midcourse maneuver using the Service
Module’s RCS thrusters to refine their trajectory for re-entry into Earth’s
The astronauts treated Earth-bound viewers with a 15-minute
television broadcast, beginning with a view of the receding Moon. They turned
the camera into the cabin, and Armstrong displayed the two boxes containing the
precious samples of lunar rocks and soil. The crew demonstrated food preparation in
their spacecraft and advancements that had been made in the types of food
available to them. During brief physics lessons, Aldrin demonstrated how
gyroscopes work, and Collins displayed the behavior of fluids in zero gravity.
They ended the broadcast by showing viewers Earth. The rest of their day was
spent leisurely before they settled in for another 10-hour rest period about
163,000 miles from home.
Apollo 11 astronauts
photographed the Earth during the homeward voyage from (left to right) 197,000
miles, 189,000 miles, 129,000 miles, and 100,700 miles away.
When they awoke for their final full day in space, they had
closed the distance to Earth to 131,000 miles as they continued to accelerate. Capcom
Owen K. Garriott informed them that mission control had decided that since
their trajectory was so precise, a planned midcourse maneuver that day was not
necessary. They soon passed the halfway point between Earth and Moon, 118,424
miles from each. During a 12-minute TV
broadcast, the astronauts provided their reflections on the mission. Collins
stressed the complexity of the flight and the hard work done by the thousands
of workers to make Apollo 11 possible. Aldrin opined that the flight represented
not just the work that went into it, but also humanity’s innate curiosity to
explore. Armstrong concluded by recognizing everyone responsible for making
Apollo 11 possible and expressed a special thanks to the workers who had built
their spacecraft. As a closing scene,
the astronauts zoomed in on the Earth, now 105,000 miles away. Armstrong’s wife
Jan and their two children, Collins’ wife Pat and their children and Aldrin’s
son Andy visited the Mission Control Center Viewing Room during their
Shortly before they retired for their last night in space,
Capcom Duke informed the astronauts that due to a weather system approaching
their nominal end-of-mission splashdown point, a new area 250 miles to the
northeast would be targeted. No midcourse maneuvers were necessary, as the CM
used its lift capability to extend the entry trajectory. Hornet, meanwhile, was already speeding toward the new location. President
of the United States Richard M. Nixon departed on his journey to meet the
Apollo 11 astronauts aboard Hornet.