Site evaluation continued throughout 1968, with considerable attention given to reducing the number of potential landing sites being considered. Keeping five sites as alternatives created problems in providing the necessary maps, photographs, and terrain models for the simulators. On the other hand, until the team at the Cape could be sure of on-time launches, alternate sites had to be kept in the plans to avoid a month's delay in launching a mission.80
Experience alone would answer many of the critical questions, and in the last half of 1968 some very important experience was gained. By early fall the reworked command and service module was ready for an earth-orbital test. The 11-day flight of Apollo 7 (October 11-22) was successful in all respects, demonstrating the performance of spacecraft, crew, and mission support facilities in extended earth-orbital flight. Among other critical activities, the crew simulated rendezvous with the S-IVB stage (which would carry the lunar module on a lunar landing mission) and fired the service module engine eight times without failure. That was especially gratifying, because if that engine failed the spacecraft could neither enter lunar orbit for a lunar landing nor return from lunar orbit after completing a landing mission.81
Even before Apollo 7 flew, project officials made one of the more daring decisions of the entire program: to send a crew to orbit the moon on the first manned flight of the Saturn V. Planners had long felt the need for such a mission to verify communications and navigation at lunar distances. In the alphabetical scheme of flights. [see Chapter 7] the "E" (fifth) mission was to approximate these conditions in high earth orbit. In August, MSC Apollo manager George Low set his people to work plans to extend the flight to lunar orbit. In a week of intensive discussions no "show-stoppers" emerged, and neither Marshall nor Kennedy Space Center officials expressed any reservations about it. By mid-month, Houston had clearance from Headquarters to prepare for a "C-prime" mission, contingent on successful qualification of the spacecraft on Apollo 7. The lunar flight, to be designated Apollo 8, would take a manned command and service module into orbit around the moon, check out critical systems at lunar distances, and return.82
It had to be done sooner or later, and as more than one official mentioned during the planning discussions, it was essential to assuring a successful lunar landing by the end of 1969. Yet the decision to send men to the moon on the Saturn V's third flight seems almost breathtaking. The flight record of the big booster at the time (two flights, one completely successful, the other plagued by malfunctions) was enough to give managers pause; and the risks to be taken on a lunar mission were far more serious than those of an earth-orbital mission. Still, among NASA officials and Apollo contractor executives, no serious doubts were raised about sending Apollo 8 to the moon at the end of 1968.83
The first men ever to see the moon at close range, Frank Borman, James A. Lovell, Jr., and William A. Anders, left Launch Complex 39A at Kennedy Space Center early in the morning of December 21, 1968, aboard Apollo command module 103. Four days later they fired their main propulsion engine and the spacecraft became a captive of the moon's gravity, in an elliptical orbit which they later changed to a near-circular orbit 60 nautical miles (111 kilometers) above the surface. For the next 20 hours they took photographs, relayed their visual observations and descriptions of the topography back to Mission Control, and gave viewers on Earth spectacular television views of the moon and of their home planet. On Christmas day in the early morning, at the end of the 10th trip around the moon, they fired the service module engine once more to return to Earth. The success of this maneuver prompted Lovell to notify Houston, "Please be informed there is a Santa Claus."84 Had it failed, he and his crewmates would have remained where they were, circling the moon until their oxygen ran out.
The space program was spared that grisly possibility, however, and the propulsion burn was so accurate that only one of three planned course-correction maneuvers had to be conducted on the way back - an adjustment of 4.8 feet per second (1.5 meters per second). After an uneventful return trip, they splashed down before dawn on December 27 in the Pacific Ocean, less than three miles (4.8 kilometers) from the recovery ship.85
As the climax of nearly two years of painful recovery from the tragedy of AS-204, Apollo 8 was a triumph the American space program badly needed. It not only restored the prestige of NASA and boosted the morale of the entire Apollo work force, it provided the confidence in spacecraft and ground-support systems that no other, less daring, mission could have provided. About all that remained before the first landing was to prove that the lunar module could carry out its part of the mission; two flights in 1969 would test that last important link in the system.
Besides its operational tasks, Apollo 8 had some photographic assignments that would give flight planners additional information about potential landing sites and settle important questions about the use of landmarks to determine the spacecraft's position. Overlapping vertical and oblique photographs were taken to determine the elevation and geographical position of features on the far side, information needed for accurate determination of the lunar module's position before it descended for a landing. [see Chapter 6] The crew was also given a list of photographic targets of opportunity, selected from sites of scientific interest, to supplement the imagery from Lunar Orbiter IV. Although the photographic objectives were not completely fulfilled, the pictures returned by Apollo 8 added considerably to the store of knowledge about lunar surface features.86
Equally valuable were the crew's visual observations of landmarks and potential landing sites. Their reports on the sharpness of landmarks, the ease of locating them, and the topographic details that could be seen from 60 nautical miles, reduced many of the uncertainties about what a lunar landing crew might be able to do by eye. Among other things, Borman's crew determined that lighting constraints (the allowable sun angle for optimum visibility) were on the conservative side; they found no difficulty in observing surface details at sun angles of 2 to 3 degrees, considerably less than the 6 degrees adopted as a lower limit. They reported that the maps and photographs they carried, together with last-minute instructions from the ground, were adequate for locating surface features.87
80. Phillips, "Minutes of the Apollo Site Selection Board Meeting of March 26, 1968," May 6, 1968.
81. Brooks, Grimwood, and Swenson, Chariots, pp. 265-72.
82. Ibid., pp. 256-60, 272-74.
84. Ibid., pp. 274-84.
85. MSC PA-R-69-1, "Apollo 8 Mission Report," Feb. 1969, p. 3-2.
86. Ibid., pp. 4-1 to 4-9.
87. Ibid., pp. 4-8 to 4-9, 7-19 to 7-20.