Landing site evaluation had begun as soon as photographs from the first Lunar Orbiters became available. [see Chapter 6] By March 1967 MSC's Lunar and Earth Sciences Division had prepared a short list of candidate sites,* which it presented to the Apollo Site Selection Board. Operational considerations predominated at this stage of planning; the sites were all within the "Apollo zone of interest" (5 degrees north to 5 degrees south latitude, 45 degrees east to 45 degrees west longitude) and appeared from the Orbiter photographs to be comparatively level and smooth. MSC recommended that sites for the first landing be chosen from that list by August 1. The board accepted that recommendation.61 For the rest of the year the Apollo Site Selection Board worked steadily, with input from Bellcomm, the Jet Propulsion Laboratory, the U.S. Geological Survey, and the Group for Lunar Exploration Planning, evaluating additional photographs from Lunar Orbiters as they became available.** Meanwhile MSC continued to study the operational constraints of its chosen sites; planners were mainly concerned with slopes and irregularities in the terrain along the approaches to the sites, which could interfere with the lunar module's landing radar. The data necessary to make the final choice of sites (principally topographic maps) were slow in coming, however, and MSC could not meet the August 1 date it had proposed.62 Instead the site selection board met at Houston on December 15 to decide on sites for the first two missions and to lay out a schedule for future activities.
MSC presented the results of its studies on approach paths, which showed that all the "Set B" sites were acceptable. Simulations showed that the lunar module's landing radar could guide the spacecraft to a landing at any of the eight sites. A considerable part of the discussion dealt with the number of sites to be retained in planning for each mission. At this stage no one could be sure that every mission would be launched on time. If a technical malfunction caused a countdown to be stopped, up to 66 hours' delay in launching might be necessary, in which case a more westerly landing site would have to be substituted for the original. This entailed complications in other aspects of mission preparation - it required the astronauts to become familiar with three different landing approaches and geologic areas, for example, and increased the requirements for maps and other data - but the alternative was to postpone the launch for at least a month.63
After summing up the detailed evaluations, John E. Eggleston, chief of MSC's Lunar and Earth Sciences Division, recommended five of the best sites ("Set C") for the first landing mission and another six for the second, which the board approved.64 Eggleston and Wilmot Hess, chief of MSC's Science and Applications Directorate, then directed the board's attention to the need to begin evaluating sites for the third and subsequent missions. Landing areas topographically different from those already chosen should be examined. Evaluation of highland sites in or near the Apollo zone should be started. Board chairman Sam Phillips agreed in principle that the third mission could be more ambitious, but he advised planners to stay on the conservative side for the time being and look for science targets in the areas covered by the Set B sites. A U.S. Geologic Survey representative suggested that in some cases shifting the landing point only a few kilometers within a selected area would bring the astronaut-explorers within walking distance of some scientifically interesting features. He also pointed out that if the first landing was made in an eastern mare the second should be targeted to a western one, since maria showed different characteristics in the two regions.65
From early 1968 onward the site selection teams would get only limited additional lunar photography, since after the fifth*** no more Orbiters would be flown. Orbiter photographic coverage, however, was not comprehensive; it did not cover every interesting site with sufficient resolution to permit detailed evaluation. Until the middle of 1967 the Office of Manned Space Flight was planning to fly an advanced lunar mapping and survey system that would furnish more detailed coverage of a greater portion of the lunar surface; but in August its potential value to Apollo was judged to be marginal and its further development was canceled to save money.66 The following March, however, Sam Phillips noted a continuing need for lunar photography and asked MSC to consider how it might be provided by astronauts in lunar orbit on scheduled Apollo flights.67 Houston enumerated several types of cameras and film that could be useful in site selection and in lunar cartography, and scientific interpretation as well.68 Planning was started for a considerable amount of lunar surface photography, including candidate sites for future landings, to be conducted on every manned lunar mission.
* "Landing sites," as somewhat loosely used in the following discussion, corresponds more nearly to the "landing areas" previously mentioned. [Chapter. 6] However, within the larger areas studied, MSC evaluators did examine several specific landing ellipses - "sites," in the sense that term was used before.
** Lunar Orbiters III, IV, and V, launched on Feb. 4, May 4, and Aug. 1, 1967, all returned photographs used in Apollo landing site selection. Four more Surveyors were landed by early 1968 as well; although they were mainly equipped for scientific studies, they also provided Apollo with useful data on properties of lunar soil.
`*** Launched Aug. I, 1967, Lunar Orbiter V completed its photographic mission on Aug. 18 and crashed into the moon Jan 31, 1968.
61. MSC, "Lunar Landing Site Selection Briefing, Compilation of Presentation Material," Mar. 8, 1967; John E. Eggleston to Dir., Science and Applications, "Trip report - Apollo Site Selection Board Meeting; Surveyor/Orbiter Utilization Committee Meeting," Apr. 3, 1967; Owen E. Maynard to Mgr., Apollo Spacecraft Program Office, "Trip report - Apollo Site Selection Board and Surveyor/Orbiter Utilization Committee Meetings," Apr. 20, 1967.
62. Low to Hqs., attn. Dr. James A. Turnock, "Selection of Lunar Landing Sites for First Lunar Landing Mission," Sept. 3, 1967.
63. Phillips to multiple addressees, "Minutes of the Apollo Site Selection Board meeting of December 15, 1967," Jan. 29, 1968; MSC, "Apollo Site Selection Board Briefing, Compilation of Presentation Material," Dec. 15, 1967.
66. Compton and Benson, Living and Working in Space, p. 87; Robert C. Seamans, Jr., to Mueller, "Termination of the Lunar Mapping and Survey System," July 25, 1967; U.S., Congress, House, Subcommittee on Manned Space Flight of the Committee on Science and Astronautics, 1968 NASA Authorization, Hearings on H.R. 4450, H.R. 6470, 90/1, pt. 2, pp. 127-28, 568-69; idem, 1969 NASA Authorization, Hearings on H.R. 15086, 90/2, pt. 2, p. 64.
67. Phillips to Gilruth, "Lunar Photography from the CSM," Mar. 29, 1968.
68. John R. Brinkmann to Chief, Syst. Eng. Div., "Lunar photography from the CSM," May 13, 1968; Warren J. North to Chief, Syst. Eng. Div., same subj., May 15, 1968.