LUNAR EXPLORATION BEGINS

Selecting Sites for Exploration

Since its primary objective was to land on the moon and return, Apollo 11 had been targeted for the least hazardous site. When the emphasis shifted to exploration, however, scientific considerations carried much greater weight in the choice of a landing site.20 Even so, every landing was as risky as the first, and if MSC vetoed a site or expressed strong reservations about its feasibility on operational grounds, Headquarters and the Apollo Site Selection Board were reluctant to override the center's recommendations for the sake of enhanced scientific return.21

During 1968 and early 1969 the Apollo Site Selection Board necessarily concentrated on choosing landing areas for the first two missions. Five prime candidates had been chosen by December 1967, from which three - an eastern, a central, and a western, to allow for possible delays in the launch - were picked for the first landing. [see Chapter 8] It was more or less taken for granted that if the first landing mission should succeed, then the second would be sent to another of those five sites, since much of the necessary planning would already have been done. If the first mission landed in an eastern mare, the second would be sent to a western one, and vice versa.

The Board's advisory groups continued to evaluate Lunar Orbiter photographs and by June of 1969 had produced a list of 22 sites for lunar exploration missions.[Table 1] These were chosen for their apparent value in contributing to answers to one or more of the 15 questions in lunar exploration. [Appendix 3] For most of these sites, changes in operational philosophy would be required. Only one site, not three, would be available at each launch opportunity; point landings (within 1 kilometer, 0.62 miles) would be necessary, to place the landing module as near the features of interest as possible; approach paths might be rough or undulating rather than smooth; free-return trajectories could not be used; and the high-resolution photography required to certify a site was generally not available.22

With more than twice as many interesting locations to visit as there were missions planned, site selection would be a complex process at best. Scientists' priorities might change as the results of early missions became known and as NASA developed more precise landing techniques and extended the area where the spacecraft could land. Reconciling the goals of science with the constraints of mission operations required an early start and continuing tradeoffs as the project progressed.

At the June 3 meeting of the Apollo Site Selection Board, chairman Sam Phillips, anticipating heavy work loads if the board was to accomplish its task within tight schedules, requested that the board meet monthly if possible. He directed Lee Scherer to prepare a thorough briefing on the scientific objectives of lunar exploration and suggested that the Group for Lunar Exploration Planning propose a sequence of missions that would accomplish those objectives. Board members agreed a that to make sensible choices between sites they needed a better understanding of the rationale of lunar exploration and the operational improvements being planned.23

The meeting then turned to the question of a site for the second mission. Scientists reiterated their preference for a western (younger) mare if the first mission landed safely at an eastern (older) site. Two western sites were on the short list of preferred sites compiled in 1968: one just below the equator some 450 kilometers (280 miles) south and slightly east of crater Kepler and the other about 250 kilometers (155 miles) northwest of the first. Benjamin Milwitzky of the Lunar Exploration Office then suggested that Apollo 12 land near a Surveyor spacecraft. As early as January 1969 Milwitzky, formerly the Headquarters program manager for Surveyor, had suggested visiting a landed Surveyor and returning some spacecraft parts and nearby surface samples to earth for study. This could yield valuable engineering information on the effects of the space environment on materials, besides allowing postmission verification of Surveyor's scientific results.24

MSC representatives then presented a rationale for considering two other western sites. Although these had been eliminated in selecting the final five sites, they met MSC's criteria for operational suitability and offered certain advantages over the first two. Both sites were near Surveyor spacecraft.25 The Board reacted unfavorably to these suggestions, pointing out that the site where Surveyor III was located was in a younger mare that was not much different from those in the eastern sites, whereas the scientists' first two choices were in typical older regions. Examining the Surveyor would detract from the other objectives of the mission. Furthermore, if returning Surveyor parts were set as a goal for the mission, failure to accomplish the necessary precision in landing could be interpreted as failure - which would not, in fact, be the case. Chairman Sam Phillips was reluctant to add any more sites to the list for the second mission. He did not favor either of MSC's choices and instead directed Houston to examine two sites considered highly desirable by the scientists, Hipparchus and Fra Mauro, and report On their suitability.26

MSC analyzed the data available for these two sites and found them unacceptable for the second landing mission. Hipparchus had only about half as much good landing area as the average Apollo 11 site and Fra Mauro was worse. Photographic coverage in both cases was marginal. Houston recommended that the site selection board give no further consideration to these two locations, but that it reexamine the Surveyor III site, which met all the criteria for the first landing and was in some respects better than the two western sites under consideration.27 Phillips concurred and directed the Group for Lunar Exploration Planning to assess the scientific merit of the site.28

On June 17 the Site Selection Subgroup of the Group for Lunar Exploration Planning met at Houston to try to reduce the complexity of lunar exploration planning. MSC's operations planners needed definite recommendations as to scientific objectives and priorities rather than the unstructured group of sites currently being considered. A short list of high-priority sites was desired, which would not subsequently be changed except through formal change procedures. MSC engineers briefed the subgroup on the increased capabilities that might be expected for the exploration missions. After Apollo 11, four "H" missions were planned, each of which would be able to carry a complete Apollo lunar surface experiments package (ALSEP), could support two periods of surface activity by the astronauts, and would be targeted for a smaller landing zone than the first mission.* On the later "H" missions engineers expected to be able to land within a 1-kilometer (0.62-mile) circle. After the "H" missions, six "J" missions would be flown. These could land with considerably improved accuracy, stay on the surface for three days and allow four excursions to the surface, and carry scientific equipment in the service module for lunar- orbital experiments. Starting with the second or third "J" mission, a powered surface vehicle would extend the astronauts' radius of operations to about 5 kilometers (3 miles).29

With these developments in mind, the subgroup reduced the list of candidate sites to 10, ordering them in a sequence that would produce the best scientific return, and added five more representing lunar features of scientific interest not covered by the existing fist. It recommended systematic photography from the orbiting command and service module to provide the necessary planning data for later missions. Finally, the subgroup recommended that Surveyor III be deleted from further consideration for the second landing because its location was not expected to yield data significantly different from the two eastern sites already picked for Apollo 11.30

The Site Selection Board met again on July 10 for a briefing on the aims of lunar exploration. Donald Wise of the Lunar Exploration Office discussed the types of information the scientists hoped to get from the lunar exploration program: the ages of lunar materials, their chemical composition, clues to the processes that have created lunar landforms, the interior structure of the moon, and the rate of flow of heat from its interior. Farouk El-Baz of Bellcomm described the general areas that should be sampled in the first phase (10 missions) of lunar exploration: two types of mare material ("older" or "eastern" and "younger" or "western"); regional stratigraphic units such as deposits around mare basins; impact craters in both maria and highlands; morphological manifestations of volcanic activity in both mafia and highlands; and areas that might give clues as to the nature and extent of processes other than impact and volcanism which may have acted on the lunar surface. He then enumerated the characteristics of each of the 10 landing sites proposed by the Group for Lunar Exploration Planning, relating each to the scientific goals of the program and tying the sequence to expected improvements in spacecraft capabilities and flight operations planning.

Chairman Phillips remarked that the list seemed well thought out and that a short list of desirable science sites must soon be stabilized. After considerable discussion, the Board approved the 10 candidate sites for planning purposes. Phillips directed MSC to study these sites and report on their suitability.

Houston had already taken a quick look at the sites and determined that all would require additional photographs before they could be certified under existing criteria. Photography from the Apollo 10 command module - conducted specifically to evaluate its usefulness for filling gaps in Lunar Orbiter coverage - had proved adequate for site analysis, and MSC's data indicated that by proper choice of sites for early missions, photographs of many of the later ones could be obtained. According to MSC's studies, the Surveyor III site offered better opportunities for this "bootstrap" photography than the other western locations on the list.31

Two months' work by the Apollo Site Selection Board did not finally determine where each Apollo exploration mission would go. It reduced the scope of the debate somewhat, established the principle that changes were to be made only for good scientific reasons, and provided the means for accommodating changes as the program developed. The list of 10 sites approved in July provided specific targets for mission planners; it would change as operational problems arose and as improved equipment and techniques became available.

Table 1.

Lunar Landing Sites Recommended for Consideration as of June 1969.**

Site                     Latitude                Longitude
                         Deg Min                 Deg Min
====                     === ===                 === ===
Censorinus                0  17 S                32  39 E
Rima Littrow             21  25 N                28  56 E
Abulfeda                 14  50 S                14  00 E
Rima Hyginus              7  52 N                 6  07 E
Tycho                    41  08 S                11  35 W
Copernicus Peak           9  36 N                19  53 W
Copernicus Wall          10  22 N                19  59 W
Schroter's Valley        24  36 N                49  03 W
Marius F                 15  10 N                56  31 W
Fra Mauro                 3  45 S                17  36 W
Mosting C                 1  55 S                 8  03 W
Hipparchus                4  36 S                 3  40 E
Gassendi                 17  50 W                40  20 W
Dionysius                 2  31 N                17  49 E
Alexander                37  46 N                14  06 E
Alphonsus                13  35 S                 4  11 W
Rima Bode II             12  47 N                 3  49 W
Copernicus CD             6  32 N                14  58 W
Tobias Mayer P           13  18 N                31  11 W
Aristarchus              24  24 N                47  50 W

* The landing zone for Apollo 11 was about 19 kilometers long and 5 kilometers wide (12 by 3 miles) as a result of uncertainties in the determination of the spacecraft's position and velocity in lunar orbit before landing.

** From minutes of the Apollo Site Selection Board meeting, June 3, 1969.

20. J. O. Cappelari, Jr., ed., "Where on the Moon? An Apollo Systems Engineering Problem," The Bell System Technical Journal 51 (1972): 976-84.

21. John R. Sevier interview, Apr. 24, 1986.

22. MA/Apollo Program Dir. to multiple addressees, "Minutes of the Apollo Site Selection Board Meeting of June 3, 1969."

23. Ibid.

24. Ibid.; Benjamin Milwitzky to Dir., Apollo Lunar Exploration Office, "Biasing Apollo Missions to Land Near Surveyor Spacecraft on the Moon," Jan. 10, 1969.

25. Minutes of the Apollo Site Selection Board Meeting, June 3, 1969; Owen E. Maynard to Mgr., Apollo Spacecraft Program, "Apollo Site Selection Board trip report - June 3, 1969," with encl., "Lunar Landing Site Recommendations for Apollo 12 as Presented to Apollo Site Selection Board June 3, 1969," June 10, 1969.

26. Minutes of the Apollo Site Selection Board Meeting, June 3, 1969.

27. George M. Low to NASA Hqs., attn.: S. C. Phillips, TWX, "Lunar Landing Sites for H-1 Mission," June 12, 1969.

28. Phillips to MSC, attn.: G. Low, TWX, "Lunar Landing Sites for H-1 Mission," June 16, 1969.

29. N. W. Hinners to Captain L. R. Scherer, "Second Mission Landing Sites," June 18, 1969; Hinners to Group for Lunar Exploration Planning and Site Selection Subgroup, "Fourth GLEP Site Selection Subgroup Meeting - June 17, 1969," June 23, 1969; Hinners to file, "GLEP Site Selection Subgroup, Fourth Meeting, June 17, 1969," Aug. 4, 1969.

30. Hinners, "Fourth GLEP Site Selection Subgroup Meeting - June 17, 1969."

31. Minutes of the Apollo Site Selection Board Meeting, July 10, 1969.