Apollo 8

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Apollo 8

Mission insignia
Mission statistics
Mission name:	Apollo 8
Command Module:	CM-103
Service Module:	SM-103
Lunar Module:	Lunar Test Article (LTA-B)
Booster:	Saturn V SA-503
Call sign:	Command module: Apollo 8
Number of crew members:	3
Launch pad:	Kennedy Space Centre, Florida LC 39A
Launch:	December 21, 1968 12:51:00 UTC
Landing:	December 27, 1968 15:51:42 UTC 8°6′N 165°1′W
Duration:	6 d 3 h 0 min 42 s
Number of lunar Orbits:	10
Time in lunar orbit:	20 h 10 min 13.0 s
Mass:	CSM 28,817 kg; LTA 9,026 kg
Crew photo
L-R: Lovell, Anders and Borman
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Apollo 8 was the second manned mission of the Apollo space program, in which Commander Frank Borman, Command Module Pilot James Lovell and Lunar Module Pilot William Anders became the first humans to orbit around the Moon. It was also the first manned launch of the Saturn V rocket.

NASA prepared for the mission in only four months. The hardware involved had only been used a few times—the Saturn V had launched only twice before, and the Apollo spacecraft had only just finished its first manned mission, Apollo 7. However, the success of the mission paved the way for the successful completion of U.S. President John F. Kennedy's goal of landing on the Moon before the end of the decade.

After launching on December 21, 1968, the crew took three days to travel to the Moon, which they orbited for 20 hours. While in lunar orbit they made a Christmas Eve television broadcast in which the crew read from the book of Genesis. It had been the most watched broadcast to date.

Crew

• Frank Borman (2) (flew on Gemini 7, Apollo 8), commander
• James Lovell (3) (flew on Gemini 7, Gemini 12, Apollo 8, Apollo 13), command module pilot
• William Anders (1) (flew on Apollo 8), lunar module pilot

*Number in parentheses indicates number of spaceflights by each individual, prior to and including this mission.

Backup crew

The backup crew trained to take the place of the prime crew in case of illness or death.

• Neil Armstrong (flew on Gemini 8, Apollo 11), commander
• Edwin E. Aldrin (flew on Gemini 12, Apollo 11), command module pilot
• Fred Haise (flew on Apollo 13), lunar module pilot

Support crew

The support crew were not trained to fly the mission but were able to stand in for astronauts in meetings and be involved in the minutiae of mission planning, while the prime and backup crews trained. They often also served as capcoms during the mission.

• John Bull (never flew in space)
• Vance Brand (flew on Apollo-Soyuz Test Project, STS-5, STS-41-B, STS-35
• Gerald Carr (flew on Skylab 4)
• Ken Mattingly (flew on Apollo 16, STS-4, STS-51-C)

Flight directors

• Cliff Charlesworth, Green team
• Glynn Lunney, Black team
• Milton Windler, Maroon team

Planning

On December 22, 1966, NASA announced the crew for the third manned Apollo flight: Frank Borman, Michael Collins and Bill Anders. Collins was replaced by his backup Jim Lovell in July 1968, after Collins had to have surgery due to suffering a cervical disc herniation, requiring two vertebrae to be fused together. Collins recovered and went on to be the Command Module Pilot for Apollo 11.

In September 1967, the Manned Spacecraft Centre in Houston, Texas proposed a series of missions that would lead up to a manned lunar landing. Seven mission types were outlined, each testing a specific set of components and tasks; each previous step needed to be completed successfully before the next mission type could be undertaken. These were:

1. Unmanned Command/Service Module (CSM) test
   
2. Unmanned Lunar Module (LM) test
   
3. Manned CSM in low Earth orbit
   
4. Manned CSM and LM in low Earth orbit
   
5. Manned CSM and LM in an elliptical Earth orbit with an apogee of 4600 mi (7400 km)
   
6. Manned CSM and LM in lunar orbit
   
7. Manned lunar landing

Of all the components of the Apollo system, the Lunar Module (LM), which would eventually be used to land on the Moon, presented the most problems. It was behind schedule, and when the first model was shipped to Cape Canaveral in June 1968, over 100 separate defects were discovered. Grumman Aircraft Engineering Corporation, which was the lead contractor for the LM, predicted that the first mannable LM, to be used for the D mission, would not be ready until at least February 1969, delaying the entire sequence.

George Low, the Manager of the Apollo Spacecraft Program Office, proposed a solution in August. Since the Command/Service Module (CSM) would be ready three months before the Lunar Module, they could fly a CSM-only mission in December 1968. But instead of just repeating the flight of Apollo 7, the C mission that would fly the CSM in Earth orbit, they could send the CSM all the way to the Moon and maybe even enter into orbit. This mission was dubbed the "C-Prime" mission. This new mission would allow NASA to test procedures that would be used on the manned lunar landings that would otherwise have to wait until Apollo 10, the F mission. There were also concerns from the CIA that the Soviets were planning their own circumlunar flight for December to upstage the Americans once again (see Zond program).

Almost every senior manager at NASA agreed with this new mission. The only person who needed some convincing was James E. Webb, the NASA administrator. However, outvoted by the rest of the agency, he gave his approval. After leading the agency for eight years, he would resign just four days before the launch of Apollo 7, the first manned Apollo flight.

Deke Slayton, the Director of Flight Crew Operations, decided to swap the crews of the D and E missions. James McDivitt, the original commander of the D mission, has said he was never offered the circumlunar flight but would probably have turned it down, as he wanted to fly the lunar module. Borman, on the other hand, jumped at the chance: his original mission would just have been a repeat of the previous flight, except in a higher orbit. This swap also meant a swap of spacecraft — Borman's crew would now use CSM-103, while McDivitt's crew would use CSM-104.

In the end, the E mission was canceled as most its objectives had been covered by the Apollo 8 and Apollo 9 flights. Mission managers were also confident that Apollo 10 would also cover the remaining objectives with its lunar orbit flight.

On September 9, the crew entered the simulators to begin their preparation for the flight. By the time the mission flew, the crew would have spent seven hours training for every actual hour of flight. Although all crew members were trained for all aspects of the mission, it was necessary to specialize. Borman, as commander, was given training on controlling the spacecraft during the re-entry. Lovell was trained on navigating the spacecraft in case communication was lost with the Earth. Anders was placed in charge of checking the spacecraft was in working order.

It was not until November 12 that a public announcement was made about the change of mission for Apollo 8. Previous to this Thomas O. Paine, the deputy Administrator of NASA, had made a fleeting remark that all options were being considered.

Borman's main concern during the four months leading up to the launch was keeping the flight plan as simple as possible, not accepting any addition that went beyond the simple objectives of performing the first manned Saturn V launch, going to the Moon and orbiting it. He made sure that they stayed in lunar orbit only as long as necessary — 10 orbits.

The crew, now living in the crew quarters at Kennedy Space Centre, received a visit from Charles Lindbergh and his wife the night before the launch. They talked about how before his 1927 flight, Lindbergh had used a piece of string to measure the distance from New York City to Paris on a globe and from that calculated the fuel needed for the flight. The total was a tenth of the amount that the Saturn V would burn every second.

The next day, Lindbergh and his wife, Anne Morrow Lindbergh, watched the Start of Apollo 8 together, and she later wrote her book Earthshine about the event.

The Saturn V

The Saturn V rocket used by Apollo 8 was designated SA-503, the third flight model. When it was erected in the Vertical Assembly Building on December 20, 1967, it was thought that the rocket would be used for an unmanned test flight carrying a boilerplate Command/Service Module. Although Apollo 6 had suffered several major problems (it suffered severe pogo oscillation during its first stage and two second stage engines shutdown early), Marshall Space Flight Centre, in charge of the Saturn V, was confident that it could solve all the issues without the need for another unmanned test flight. The SA-503 mission was thus changed to a manned one.

However, NASA managers did impose some restrictions on a manned flight taking place: the S-II second stage had to undergo cryogenic testing at the Mississippi Test Facility and other changes were to be made to "man-rate" the vehicle. So on April 30, the Saturn V was unstacked and the S-II second stage shipped by barge to the test site. The spark igniters on the second and third stage engines were also modified. In May 1968 a leak was found in a first stage engine, requiring it to be replaced.

With only two launches of the Saturn V under its belt, the ground crew at Kennedy Space Centre (KSC) was having problems keeping to the schedule. The Grumman crew was also having issues with the lunar module. Concern was expressed at the fact so much work had to be done on the lunar module after it had shipped to the Cape. The ascent engine developed leaks that caused redesigns and valve changes.

Then in August 1968, the entire mission changed. SA-503 would launch men to the Moon and would not be carrying a lunar module, instead carrying a mass equivalent, called a lunar module test article (LTA), similar to ones used for Apollo 4 and Apollo 6. In order to speed up the pre-launch preparations, much of the modification of the Saturn V was taken out of the hands of KSC and given to appropriate development centers; only changes that affected crew safety were made.

The Apollo 8 spacecraft was placed on top of the rocket on September 21 and the rocket made the slow 3-mile (5 km) journey to the launch pad on October 9. Testing continued all through December until the day before launch.

The SA-503 designation stood for Saturn-Apollo, and was used by NASA departments concerned with the launch vehicle. However, departments concerned with the manned flight often used AS-503, standing for Apollo-Saturn; both of these designations were used at the time to refer to the mission as a whole. The -503 number indicated that it was flight number 3 (503) of the Saturn V (503).

The mission

Launch and trans-lunar injection

Apollo 8 launched at 7:51:00 a.m. Eastern Standard Time on December 21, 1968. The entire launch phase was practically flawless with only minor problems. The S-IC first stage's engines underperformed by 0.75%, causing the engines to burn for 2.45 seconds longer than planned. Towards the end of the second stage burn, the rocket underwent pogo oscillations that Frank Borman estimated were of the order of 12 Hz and about ±0.25 g (±2.5 m/s²). The first manned Saturn V placed the spacecraft into a 112.8 mi by 118.9 mi (181.5 km by 191.3 km) Earth orbit with a period of 88 minutes and 10 seconds. The apogee was also slightly higher than intended, with a planned circular orbit of 115 mi (185 km). The S-IC impacted the Atlantic Ocean at 30°12′N 74°7′W and the S-II at 31°50′N 37°17′W.

For the next 2 hours and 38 minutes the crew and Mission Control worked to check that the spacecraft was in working in order and ready for Trans-Lunar Injection (TLI), the burn that would put the spacecraft on a trajectory to the Moon. At the same time the crew transformed the capsule from a rocket payload to a spacecraft. And the S-IVB third stage had to be in working order. On the previous unmanned test, the S-IVB had failed to re-ignite.

During the flight there would be three capsule communicators (usually referred to as "capcoms") on a rotating roster. These were the only people who would normally communicate with the crew. Michael Collins was the first of these on duty and at 2 hours, 27 minutes and 22 seconds after launch radioed "Apollo 8. You are Go for TLI". Mission Control had given official permission for the crew to go to the moon. Over the next twelve minutes before the burn, the crew continued to monitor the spacecraft and the rocket. The S-IVB third stage rocket ignited on time and burned perfectly for 5 minutes and 17 seconds. The burn increased the velocity of the spacecraft to 35,505 ft/s (10,822 m/s) and their altitude at the end of the burn was 215.4 mi (346.7 km). They were the fastest humans in history.

Now that the S-IVB had performed its required tasks it was jettisoned. The crew then rotated the spacecraft to take some photographs of the spent stage, as well as practiced flying in formation with it. As the crew rotated the spacecraft around they had their first views of the Earth as they moved away from it. This was the first time humans had been able to see the entire Earth in one go.

Borman became worried that the S-IVB was staying too close to the CSM and suggested to Mission Control that the crew perform a separation maneuver. Mission Control at first suggested pointing the spacecraft towards Earth and using the Reaction Control System (RCS) thrusters on the Service Module to add 3 ft/s (0.9 m/s) away from the Earth, but Borman did not want to lose sight of the S-IVB. After much discussion it was decided to burn in this direction anyway but at 9 ft/s (2.7 m/s). These discussions ended up putting the crew an hour behind their flight plan.

Five hours after launch, mission control commanded the S-IVB booster to vent its remaining fuel through its engine bell to change its trajectory such that it would flyby the Moon and enter into a solar orbit, so as to pose no future hazard to the crew. It went into a 0.99 by 0.92 AU solar orbit with an inclination of 23.47° and a period of 340.80 days.

The members of the Apollo 8 crew were the first humans to pass through the Van Allen radiation belts, which extend up to 15,000 mi (25,000 km) from Earth. Although it was predicted that the passage through the belts would cause a radiation dosage of no more than a chest X-ray or 1 milligray (during the course of a year, the average human receives a dose of 2 to 3 mGy), there was still interest in the radiation dosages on the crew. So each crewmember wore a Personal Radiation Dosimeter that could be read back to the ground as well as three passive film dosimeters that show the cumulative radiation experienced by the crew. By the end of the mission, the average radiation dose of the crew was 1.6 mGy.

Coasting to the Moon

Jim Lovell's main job as Command Module Pilot was to act as navigator. Although Mission Control performed all the actual navigation calculation, it was necessary that in case of communication loss the crew could navigate their way home. This was done by star sightings using a sextant built into the spacecraft, measuring the angle between a star and the Earth's (or the Moon's) horizon. This proved to be difficult, as the venting by the S-IVB had caused a large cloud of debris to form around the spacecraft, making it hard to distinguish the stars.

By seven hours into the mission, the delay in moving away from the S-IVB and Lovell's star sightings meant that they were behind schedule on the flight plan by about one hour and 40 minutes. The crew now placed the spacecraft into Passive Thermal Control (PTC), or what is more aptly called barbecue mode. This had the spacecraft roll about one rotation per hour, along its long axis in order to ensure even heat distribution of the spacecraft. In direct sunlight, the spacecraft could be heated to over 200 °C while the parts in shadow would be -100 °C. These temperatures could cause the heat shield to crack or propellant lines to burst. As it was impossible to get a perfect roll, the spacecraft actually swept out a cone as it rotated. This would have to be trimmed every half hour as it started to get larger and larger.

The first mid-course correction came 11 hours into the flight. Testing on the ground had shown there was a small chance that the Service Propulsion System (SPS) engine would explode when burned for long periods unless its combustion chamber was 'coated' first. This could be done by burning the engine for a short period. This first correction burn was only 2.4 seconds and added about 20.4 ft/s (6.2 m/s) prograde (in the direction of travel). This was less than the 24.8 ft/s (7.5 m/s) planned, and the shortfall was due to a bubble of helium in the oxidizer lines causing lower than expected fuel pressure, requiring the crew to use the small Reaction Control System (RCS) thrusters to make up the shortfall. Two later planned midcourse corrections were cancelled as the trajectory was found to be perfect.

Eleven hours into the flight, the crew had been awake for over 16 hours, having been awakened about 5 hours before launch. So it was time for Frank Borman to start his scheduled 7-hour sleep period. It proved difficult to sleep. NASA had decided that at least one crewmember should be awake at all times to deal with any issues that might arise. But the constant radio chatter with the ground and the air circulation fans made it hard to sleep. As well as this, sleeping in space is a somewhat unnatural experience—you cannot rest your head on a pillow and Bill Anders said that he would suddenly jolt awake with the sensation that he was falling.

About an hour after starting his sleep period, Borman requested clearance to take a Seconal sleeping pill, but the pill had little effect. After Borman slept for seven hours fitfully, he awoke feeling ill. He vomited twice, and had a bout of diarrhea that left the spacecraft full of small globules of vomit and feces. The crew cleaned up as best as they could. Borman decided that he did not want the world to know about his medical problems but Lovell and Anders still wanted to tell the ground. They decided to use the Data Storage Equipment (DSE), which could be used by the crew to tape voice recordings and telemetry, which were then dumped to the ground at high speed. After recording a description of Borman's illness they requested that mission control check the recording, as the crew "would like an evaluation of the voice comments".

A conference between the crew and medical personnel was held using the unoccupied second floor control room (there were two identical control rooms in Houston on the second and third floor, of which only one is used during the course of a mission). During a private communication with the crew, it was decided that there was little to worry about and that it was either a 24-hour flu as Borman thought, or just a reaction to the sleeping pill. In fact it is now thought that he was suffering from Space Adaptation Syndrome, which affects about a third of astronauts during their first day in space as their vestibular system adapts to weightlessness. It had never arisen on previous spacecraft ( Mercury and Gemini) as they had been too small to move freely in.

The cruise phase was a relatively uneventful part of the flight, with little happening except for the crew checking that the spacecraft was in working order and they were on course. During this time, NASA scheduled a television broadcast for 31 hours after launch. The camera used was 2 kg and broadcast in black-and-white only, using a Vidicon tube. It had two lenses: a very wide-angle (160°) lens and a telephoto (9°) lens.

During this first broadcast the crew gave a tour of the spacecraft and attempted to show how the Earth appeared. However this proved impossible, as the narrow-angle lens was difficult to aim without the aid of a monitor to show what it was looking at. Also without proper filters, the image became saturated by any bright source. In the end all the crew could do was show the people watching back on Earth a bright blob. After broadcasting for 17 minutes the rotation of the spacecraft took the high-gain antenna out of view of the receiving stations on Earth and they ended the transmission with Lovell wishing his mother happy birthday.

By this time the planned sleep periods had completely been abandoned. 32½ hours into the flight, Lovell went to bed, 3½ hours before he had planned to. A short while later Anders also went to bed after taking a sleeping pill.

Somewhat strangely the crew were unable to see the Moon for much of the outward cruise. Three of the five windows had fogged up, due to outgassed oils from the silicone sealant, and due to the attitude required for the PTC, the Moon was almost impossible to see from inside the spacecraft. In fact it was not until the crew had gone behind the Moon that they would be able to see it for the first time.

A second television broadcast came at 55 hours. This time the crew had managed to rig up filters meant for the still cameras, so that they could acquire images of the Earth through the telephoto lens. Although difficult to aim, as they had to maneuver the entire spacecraft, the crew was able to broadcast back to Earth the first television pictures of the Earth. The crew spent the transmission describing the Earth and what was visible and the colors that could be seen. The transmission lasted 23 minutes.

Lunar sphere of influence

At about 55 hours and 40 minutes into the flight, the crew of Apollo 8 became the first humans to enter the gravitational sphere of influence of another celestial body. Or to put it another way, the Moon's gravitational force became stronger than that of the Earth. At the time it happened, they were 38,759 mi (62,377 km) from the Moon and had a speed of 3,990 ft/s (1,216 m/s) with respect to the Moon. This historic moment was of little interest to the crew as they still calculated their trajectory with respect to the launch pad at Kennedy Space Centre and would do so until they performed their last midcourse correction, when they would switch to a reference frame based on ideal orientation for the second engine burn they would make in lunar orbit. It was only thirteen hours until they would be in lunar orbit.

The last major event before Lunar Orbit Insertion was a second midcourse correction. It was in retrograde (against direction of travel) and slowed the spacecraft down by 2.0 ft/s (0.6 m/s), in effect lowering the closest distance that the spacecraft would pass the moon. At exactly 61 hours after launch, about 24,200 mi (39,000 km) from the Moon, the crew burned the RCS for 11 seconds. They would now pass 71.7 mi (115.4 km) from the lunar surface.

At 64 hours into the flight, the crew began to prepare for Lunar Orbit Insertion-1 (LOI-1). This maneuver had to be performed perfectly, and due to orbital mechanics had to be on the far side of the Moon, out of contact with the Earth. After Mission Control was polled for a Go/No Go decision, the crew was told at 68 hours, they were Go and "riding the best bird we can find". At 68 hours and 58 minutes, the spacecraft went behind the Moon and out of radio contact with the Earth.

With ten minutes before the LOI-1, the crew began one last check of the spacecraft systems and made sure that every switch was in the correct place. Then they finally got their first glimpses of the Moon. They had been flying over the unlit side, and it was Lovell who saw the first shafts of sunlight obliquely illuminating the lunar surface. But the burn was only two minutes away so the crew had little time to appreciate the view.

Lunar orbit

Igniting at 69 hours, 8 minutes and 16 seconds after launch, the SPS burned for 4 minutes and 13 seconds, placing the crew of Apollo 8 in orbit around the Moon. The crew described this as being the longest four minutes of their lives. If the burn had not lasted exactly the right amount of time, the spacecraft could have ended up in a highly elliptical lunar orbit or even flung off into space. If it lasted too long they could have ended up impacting the Moon. After making sure the spacecraft was working, they finally had a chance to look at the Moon, which they would orbit for the next 20 hours.

On Earth, Mission Control continued to wait. If the crew had not burned the engine or the burn had not lasted the planned length of time the crew would appear early from behind the Moon. However this time came and went without Apollo 8 reappearing. And then exactly at the predicted moment, the signal was received from the spacecraft indicating it was in a 193.3 mi by 69.5 mi (311.1 km by 111.9 km) orbit about the Moon.

After reporting on the status of the spacecraft, Lovell gave the first description of what the lunar surface looked like:

The Moon is essentially grey, no colour; looks like plaster of Paris or sort of a grayish beach sand. We can see quite a bit of detail. The Sea of Fertility doesn't stand out as well here as it does back on Earth. There's not as much contrast between that and the surrounding craters. The craters are all rounded off. There's quite a few of them, some of them are newer. Many of them look like—especially the round ones—look like hit by meteorites or projectiles of some sort. Langrenus is quite a huge crater; it's got a central cone to it. The walls of the crater are terraced, about six or seven different terraces on the way down.

Lovell continued to describe the terrain that they were passing over. One of the crew's major tasks was reconnaissance of the planned landing sites on the Moon, especially one in Mare Tranquillitatis that would be the Apollo 11 landing site. The launch time of Apollo 8 had been chosen to give the best lighting conditions for the site. A film camera had been set up in one of the windows to record a frame every second of the Moon below. Bill Anders would spend much of the next 20 hours taking as many photographs as possible of targets of interest. By the end of the mission the crew would take 700 photographs of the Moon and 150 of the Earth.

Throughout the hour that the spacecraft was in contact with the Earth, Borman kept asking how the data for the SPS looked. He wanted to make sure that the engine was working and could be used to return early to the Earth if necessary. He also asked that they receive a Go/No Go decision before they passed behind the Moon on each orbit.

As they reappeared for their second pass in front of the Moon, the crew set up the television to broadcast a view of the lunar surface. Anders described the craters that they were passing over. At the end of this second orbit they performed the eleven-second LOI-2 burn of the SPS to circularize the orbit to 70.0 mi by 71.3 mi (112.6 km by 114.8 km).

Over the next two orbits the crew continued to keep check of the spacecraft and to observe and photograph the Moon. During the third pass, Borman read a small prayer for his church, as he was meant to lay read during the Midnight service at St. Christopher's Episcopal Church near Seabrook, Texas but due to the Apollo 8 flight was unable. A fellow parishioner and engineer at Mission Control, Rod Rose, suggested that Borman read the prayer which could be recorded and then replayed during the service.

It was as the spacecraft came out from behind the Moon for its fourth pass across the front that the crew witnessed an event never before seen—Earthrise. Anders glanced out the window and saw a blue and white orb and realized it was the Earth. Instantly the crew understood that they needed to take a photograph of this. Anders took both the first photograph, which was black-and-white, and then later the more famous colour photo. (After the flight, Borman and Anders both claimed they took the first earthrise photo - Lovell also did, but more as a joke than anything else - but it was determined that it was probably Anders.) It should be noted that, due to the synchronous rotation of the Moon about the Earth, Earthrise is not visible from the Lunar surface. The phenomenon is only visible when orbiting the Moon.

Anders continued to take photographs while Lovell took the controls of the spacecraft so that Borman could get some rest. As always, resting was difficult in the cramped and noisy capsule, though Borman was able to doze for two orbits. He would awaken at times to ask a question about their status, only to be told that everything was going fine.

Borman did wake up however when he started to hear his fellow crewmembers make mistakes. They were beginning to not understand questions and would have to ask for the answers to be repeated. Borman realized that everyone was extremely tired having not had a good night's sleep in over three days. Taking command, he ordered Anders and Lovell to get some sleep and that the rest of the flight plan regarding observing the Moon be scrubbed. At first Anders protested saying that he was fine, but Borman would not be swayed. At last Anders agreed as long as the commander would set up the camera to continue to take automatic shots of the Moon. Borman also remembered that there was a second television broadcast planned, and with so many people expected to be watching he wanted the crew to be alert. For the next two orbits Anders and Lovell slept while Borman sat at the helm.

As they rounded the Moon for the ninth time, the second television transmission began. Borman introduced the crew, followed by each man giving his impression of the lunar surface and what it was like to be orbiting the Moon. Borman described it as being "a vast, lonely, forbidding type of existence or expanse of nothing". And then after talking about what they were flying over, Anders said that the crew had a message for all those on Earth.

The only thing left for the crew now was to perform the Trans-Earth Injection or TEI, which would occur 2½ hours after the end of the television transmission. This was the most critical burn of the whole flight. If the SPS failed to ignite, then the crew would be stuck in orbit around the Moon, with only about 5 more days of oxygen and no chance of escape. And once again the burn had to be performed while the crew was out of contact with Earth, on the far side of the Moon.

The burn occurred perfectly on time. The spacecraft telemetry was reacquired as it re-emerged from behind the Moon at 89 hours, 28 minutes, and 39 seconds, the exact time predicted. When voice contact was regained, Lovell announced, "Please be informed, there is a Santa Claus", to which Ken Mattingly, the capcom, replied, "That's affirmative, You are the best ones to know". It was Christmas Day, 1968.

Unplanned manual re-alignment

Later, Lovell used some otherwise idle time to do some navigational sightings, maneuvering the module to view various stars by using the computer keyboard. However, an accidental entry erased some of the computer's memory, which caused the inertial measuring unit (IMU) to think the module was in the same relative position it had been in before lift-off and fire the thrusters to "correct" the module's attitude.

Once the crew realized why the computer had changed the module's attitude, they realized they would have to re-enter data that would tell the computer its real position. It took Lovell ten minutes to figure out the right numbers, using the thrusters to get the stars Rigel and Sirius aligned, and another fifteen minutes to enter the corrected data into the computer.

Sixteen months later, Lovell would once again have to perform a similar manual re-alignment, under more critical conditions, during the Apollo 13 mission, after that module's IMU had to be turned off to conserve energy. In his 1994 book, Lost Moon: The Perilous Voyage of Apollo 13 (later re-titled Apollo 13 when the movie based on it, Apollo 13, came out), Lovell wrote, "My training [on Apollo 8] came in handy!" In that book he dismissed the incident as a 'planned experiment', requested by the ground crew. However, in subsequent interviews Lovell has acknowledged that the incident was an accident, caused by his mistake, as described in Robert Zimmerman's 1998 book Genesis: The Story of Apollo 8.

Cruise back to Earth and re-entry

The cruise back to Earth was mostly a time for the crew to relax and monitor the spacecraft. As long as the trajectory specialists had calculated everything correctly, the spacecraft would re-enter 2½ days after TEI and splashdown in the Pacific.

On Christmas afternoon, the crew made their fifth and final television broadcast. This time they gave a tour of the spacecraft, showing how an astronaut lived in space. When they had finished broadcasting they found a small present from Deke Slayton in the food locker—real turkey with stuffing and three miniature bottles of brandy (which remained unopened). There were also small presents to the crew from their wives.

After two uneventful days the crew prepared for re-entry. The computer would control the re-entry and all the crew had to do was put the spacecraft in the correct attitude, blunt end forward. If the computer broke down, Borman would take over.

After separating from the Service Module, all the crew could do was sit and wait. Six minutes before they hit the top of the atmosphere, the crew saw the Moon rising above the Earth's horizon, just as had been predicted by the trajectory specialists. As they hit the thin outer atmosphere they noticed it was becoming hazy outside as glowing plasma formed around the capsule. The capsule started slowing down and the deceleration peaked at 6 g (59 m/s²). With the computer controlling the descent by changing the attitude of the capsule, Apollo 8 rose briefly like a skipping stone before descending to the ocean. At 30,000 feet (9 km) the drogue parachute stabilized the spacecraft and was followed at 10,000 feet (3 km) by the three main parachutes. The spacecraft splashdown position was estimated to be 8°6′N 165°1′W.

When it hit the water, the parachutes dragged the spacecraft over and left it upside down, in what was termed Stable 2 position. As they were buffeted by a 10-foot (3 m) swell, Borman was sick, waiting for the three floatation balloons to right the capsule. It was 43 minutes after splashdown before the first frogman from the USS Yorktown arrived, as the capsule had landed before sunrise. Forty-five minutes later they were on the deck of the aircraft carrier.

The command module is now displayed at the Chicago Museum of Science and Industry, along with a collection of personal items from the flight donated by Lovell and the spacesuit worn by Frank Borman. Jim Lovell's spacesuit can be found at NASA's Glenn Research Centre.

Historical importance

Apollo 8 came at the end of 1968, a year that had seen much upheaval around the world. Yet TIME magazine chose the crew of Apollo 8 as their Men of the Year for 1968, recognizing them as the people that most influenced events in the preceding year. They had been the first people to ever leave the gravitational influence of the Earth and orbit another celestial body. They had survived a mission that even the crew themselves had rated as only having a fifty-fifty chance of fully succeeding. The effect of Apollo 8 can be summed up by a telegram from a stranger, received by Borman after the mission, that simply stated, "Thank you Apollo 8. You saved 1968."

One of the most famous aspects of the flight was the Earthrise picture that was taken as they came around for their fourth orbit of the Moon. Although it was not the first image taken of the whole Earth nor would it be the last, this was the first time that humans had taken such a picture. Some regard the picture as being the start of the environmentalist movement, with the first Earth Day in 1970.

The mission was the most widely covered by the media since the first American orbital flight, Mercury Atlas 6 by John Glenn in 1962. There were 1200 journalists covering the mission, with the BBC coverage being broadcast in 54 countries in 15 different languages. The Soviet newspaper Pravda even covered the flight without the usual anti-American editorializing. It is estimated that a quarter of the people alive at the time saw — either live or delayed — the Christmas Eve transmission during the ninth orbit of the Moon; it had a tremendous impact. Touring the world after the mission, Borman met with Pope Paul VI; he was told "I have spent my entire life trying to say to the world what you did on Christmas Eve."

Atheist Madalyn Murray O'Hair later caused controversy by bringing a lawsuit against NASA over the reading from Genesis; she wished the courts to ban US astronauts—who were all Government employees—from public prayer in space. This was eventually rejected by the courts, but it caused NASA to be skittish about the issue of religion throughout the rest of the Apollo program. Buzz Aldrin, on Apollo 11, took communion on the surface of the moon after landing; he refrained from mentioning this publicly for several years, and only obliquely referred to it at the time.

Mission parameters

• CSM Mass: 63,531 lb (28,817 kg)

Earth parking orbit

• Perigee: 112.8 mi (181.5 km)
• Apogee: 118.9 mi (191.3 km)
• Inclination: 32.51°
• Period: 88.17 min

Lunar orbit

• Perilune: 69.5 mi (111.9 km)
• Apolune: 193.3 mi (311.1 km)
• Inclination: 12°
• Period: 128.7 min

Translunar injection burn

• December 21, 1968, 15:41:38 UTC

The Saturn V, S-IVB third stage, was fired for a second time. It burned for a total of 318 seconds. Apollo 8 was propelled from an Earth parking orbit velocity of 25,567 ft/s (7793 m/s) to a translunar trajectory velocity of 35,505 ft/s (10,822 m/s).

Movie

NASA created movies to summarize each mission, often shown at science museums such as the Pacific Science Centre in Seattle. The movie for Apollo 8 used soundtrack music from the Beatles' Yellow Submarine.

Mission insignia

The triangular shape of the insignia symbolizes the shape of the Apollo command module. It shows a red figure 8 looping around the earth and moon representing the mission number as well as the circumlunar nature of the mission. On the red number 8 are the names of the three astronauts.

The initial design of the insignia was developed by Jim Lovell. Lovell reportedly sketched the initial design while riding in the backseat of a T-38 flight from California to Houston, shortly after learning of the re-designation of the flight to become a circumlunar mission.