Apollo 8

In Houston, it is the twenty first of December, 1968, and half an hour before midnight. It is 05:30 GMT on the 22nd. In terms of distance, Apollo 8 is about a third of the way to the Moon and its crew are the first humans to see a true portrait of their home planet, as a sphere sitting out in space.

The commander of the mission, Frank Borman, is catching a few hours of poor quality sleep which began two and a half hours after it was supposed to. He took a sleeping pill at about 12½ hours GET. His crewmates, Command Module Pilot Jim Lovell and Lunar Module Pilot Bill Anders, are trying to keep the noise and bustle in the spacecraft down so as not to disturb him. Meanwhile, in the MOCR (Mission Operations Control Room) at Mission Control, Houston, Flight Director Glynn Lunney has just taken charge of the mission and has brought his "Black Team" to the consoles. At the CapCom console is Jerry Carr. Other major team members are as follows:

Just before the shift change, Jim had explained how it was difficult to spot the dimmer navigational stars in the spacecraft's scanning telescope. This is a unity-power, movable instrument mounted opposite the spacecraft hatch. One of these stars, Navi, also known as Gamma Cassiopeiae, would be used with the telescope to align the backup gyro system if their main attitude reference system were to fail. In support of this possibility, a test of the scanning telescope's visibility was planned to occur soon, once Jim had realigned the spacecraft's gyroscopically stabilised guidance platform. Mission Control are bringing the test forward in light of Jim's comments and they have given him an attitude to manoeuvre to that should bring Navi to the centre of the telescope's field of view, assuming he has centred the movable optics first.

Very long comm break.

Navi is near the north celestial pole. Since the flight is occurring near the winter solstice, the Sun is in line with the constellation Capricornus (which is south of the celestial equator and about as southerly as the Sun gets in the year). When looking at Navi, the optics should be well clear of major glare sources.

Lovell, from the 1969 Technical Debrief: "There's been a lot of discussion concerning what you can see through the scanning telescope as far as recognizing stars and constellations. During the early part of the flight I could not see anything through the scanning telescope that I could recognize, for instance - a constellation. I could see several stars, but I couldn't pinpoint them because I didn't know the surrounding stars. As long as we did not move the spacecraft around, got some distance from the Earth and its light, it was possible to see constellations in the scanning telescope. Several factors are involved here. One, of course, is that you must become dark-adapted. You must be dark-adapted before you can see stars. When you first look through the scanning telescope, you see nothing but blackness. A second factor is the spacecraft attitude with relationship to the Sun and/or the Earth and the Moon. When we're close to the Earth and we're maneuvering near the Earth, there's enough reflected light in the scanning telescope to make stars not visible in the scanning telescope. This is very similar to earth orbital flights. As we moved away from the Earth, about halfway between the Earth and the Moon or a little bit less, it was very easy to see constellations or stars in the dark areas of the sky. As soon as we got close to the Sun, then Sun shafting was very noticeable, and light in the sextant was noticeable and the stars are washed out. Then we had to rely on the auto optics to pinpoint the proper star, which we could easily see in the sextant. I had no problem in almost any attitude seeing stars in the sextant, the bright ones. But I did have a hard time identifying the stars in the scanning telescope."

Jim carries out the fourth realignment of the IMU platform which is completed at about 016:49. To summarise, Jim aims the sextant at two stars, first Navi and then Polaris and he makes a mark at each. The computer knows where these stars should be and, through Jim's marks, where they appeared to be relative to its platform. It can then calculate how far the gimbals that support the platform should be torqued to achieve perfect alignment.

The computer also gives Jim a check of the accuracy of his sightings. It compares the angle between Jim's marks with the known angle between the stars. An answer of zero means Jim's work has been perfect and that is exactly the result in this case.

Comm break.

Long comm break.

Quindar keys are the short tones from the CapCom position that are used to signal to the remote ground station when to send Houston voice to the spacecraft. There is a permanent radio carrier up to the spacecraft but it is not considered desirable to permanently route Houston voice on this uplink, given the interference and other chatter that can be on that line. The Quindar keys, or tones, perform this switching.

Jim is about to start his second navigation exercise, though it will be the first to produce true navigation results. The earlier results were used to determine how accurately Jim was marking on Earth's indistinct horizon. Program 23 in the computer is used for this exercise.

At 012:06:27, Bill pointed out to Mission Control that as they turned slowly in the barbecue mode, they didn't get much opportunity to see Earth.

Comm break.

The exterior appearance of the sextant is of a rotating disc with a slit across it. As the shaft axis of the instrument is rotated, the disc rotates also. The sideways movement of the trunnion axis is accommodated along the slit. As Jim rotates the shaft, particles are coming away from the area of the disc, probably around its circumference.

Long comm break.

The centre window directly opposes the Lower Equipment Bay where Jim uses the optics. It is the window he needs to cover most to keep the LEB dark and his eyes adjusted.

Conventionally, in Apollo, H means height and usually height of spacecraft from the ground. Delta-H implies change of height. Jim is unsure what is intended in giving him this information.

This crew originally trained for a mission that would include a Lunar Module and a rendezvous. In this context, the term "Delta-H" has an entirely different significance. This update is not planned so it is not surprising Jim has to query what it means.

When Jim carries out his navigation sightings using P23 in the computer, he measures the angle between Earth's horizon and a star. However, Earth's horizon is indistinct and he cannot clearly define where the actual surface of Earth is, so he marks on where he feels he can find a repeatable transition. His first set of marks helped Mission Control determine how far above from the surface he was marking, a figure called Delta-H and estimated at 18.2 kilometres. Prior to the flight, the computer had been preloaded with a distance of 32.8 km based on simulations Jim had taken part in at Massachusetts Institute of Technology. Mission Control want Jim to update the computer with the new value for Delta-H.

To interpret the instructions Jim has been given; Verb 24, means load a value from the keyboard. This value is Noun 01 which means a specific address in memory should be specified. 1354, 00000 is the memory location to be addressed, 21450 is the value for Delta-H, given as an octal number.

Very long comm break.

Comm break.

Rather than operating the DSE (Data Storage Equipment, the voice and data recorder carried onboard) himself, Bill gets the flight controllers in Houston to do it for him remotely.

Very long comm break.

Bill and Jim are probably working from page G-28 (or perhaps G-31) in the CMP checklist. Prior to commencing the P23 procedure, there are a number of items to check. As Bill says, this includes ensuring the DSE is in LBR (Low Bit Rate), Record and Forward. With the recorder started, we begin to get onboard conversations recorded.

Each time Jim makes a successful measurement of the angle between Earth's horizon and a star, the computer calculates a state vector. It then compares this with the spacecraft's current vector and calculates the difference between the position and velocity indicated by each. If Jim's marks are giving a state vector that describes the same trajectory as the ground, we would expect the computer to return values of zero. This appears to be what prompts Jim's "All balls." remark, the crew's term for showing a row of zeros in a display.

The computer is then made to display a measured angle and the time of measuring so the crew can record it.

According to the Flight Plan, for the first star (number 22, Regulus in Leo), Jim is to take three sets of marks making that nine marks in total. For the second star (number 16, Procyon in Canis Minor), he is to take two sets which represents another six marks.

Evidently, Jim has marked on Procyon first, and is now moving on to Regulus.

Jim should 'automaneuver' to an attitude suitable for getting Regulus and Earth in the sextant. He may be deciding whether he should do it manually instead as he does not want to take the spacecraft's attitude into a region where gimbal lock can occur.

Gimbal lock is a notoriously difficult concept to explain. In short form, it is what happens when the axes of the inner and outer gimbals that support the guidance platform line up. If this occurs, the gimbal system loses its ability to separate rotations of the spacecraft from the platform, leaving the latter no longer able to maintain its constant attitude in space. If this were to occur, Jim can realign the platform - not a problem when there is plenty of time available.

With the automaneuver capability, the computer should ensure they avoid gimbal-lock attitudes.

Bill appears eager to see if the computer will achieve the automaneuver. "Proceed" will instruct the computer to start the spacecraft turning.

This is the end of the DSE recording. It also marks where Frank feels awake enough to participate in the flight. However, he has woken up from his poor sleep feeling unwell. He vomits twice, has a bout of diarrhea and the episode is making the interior of the spacecraft particularly smelly and uncomfortable. Two excellent books that deal with Frank's illness, Genesis: The Story of Apollo 8 by Robert Zimmerman and A Man On The Moon by Andy Chaikin, discuss this episode further, describing how Jim and Bill chase after floating vomit and feces and how Bill became fascinated by the physics displayed by the blobs of vomit in front of him.

If the spacecraft were to continue coasting, making no further changes to its trajectory, Houston calculate that they would be whipped around the Moon, passing only 69.7 nautical miles (129.1 km) above its surface, and return to Earth. Upon reaching the home planet, their flight path would meet the atmosphere at an angle of minus 14°. Such an angle is fatally steep, and the desired entry angle is 6.5 degrees. Fortunately, by adding just a few feet per second to their velocity, something that can be done with the RCS thrusters, Apollo 8 can be put onto a path with a less steep entry angle.

Long comm break.

Very long comm break.

Based on careful measurement of Earth's image, it appears that two photographs of the planet are taken about now. Direct comparison of the two show no discernable rotation of the planet, indicating that they were taken at about the same time.

With the P23 complete, the spacecraft is manoeuvred to an attitude side-on to the Sun and made to roll at one revolution per hour.

Frank is asserting his Commander's prerogative to be constantly informed about the status of his ship. It doesn't appear that this kind of status update was written into the Flight Plan. After they arrive in lunar orbit, Frank will insist that an update is given every revolution.

Their high RCS consumption was caused by the additional manoeuvering they did to evade the S-IVB third stage.

Four hours ago, Bill and Ken Mattingly in the MOCR had discussed how Fuel Cell 2 was running a little hot.

Comm break.

After Jim finished his navigation sightings, he had a final task to use P21 in the computer to calculate his trajectory forward to their closest approach to the Moon, or pericynthion. Jim's onboard figure of 38.4 compares well with the figure now being arrived at by Earth-based tracking of 64 nautical miles.

Comm break.

As well as the IMU, the spacecraft can derive attitude information from the strapped-down gyros in the gyro assemblies. Normally, these are aligned to the IMU platform by occasional presses of the GDC Align pushbutton. If the IMU is unusable, there is a procedure that allows them to be aligned using one of two pairs of stars, a set in the southern sky and another in the north. Jim has already pointed out that Navi, one of the north set, is difficult to see in the scanning telescope so Mission Control has come up with an alternative pair of brighter stars to use instead. Sirius and Rigel are actually very near the celestial equator but as they are on the opposite side of the spacecraft from the Sun, they make suitable substitutes.

Comm break.

Frank will switch on the fans within the four cryogenic storage tanks, two for hydrogen and two for oxygen, in the Service Module. He does them one at a time for about two minutes each. This improves the accuracy of quantity measurements.

Long comm break.

Frank is most likely sitting in the commander's seat on the left side of the spacecraft. The displays used to monitor the battery charge are on the right hand of the spacecraft, and can't be observed from his position.

Long comm break.

Very long comm break.

Very long comm break.

This unusual transmission comes at about 19 hours, 38 minutes. It is about 2 am in Houston.

The oxygen purge of the fuel cells is part of an on-going routine of purges that flush contaminants from the reaction surfaces.

Comm break.

Long comm break.

Comm break.

Very long comm break.