FIRST PHASE OF LUNAR EXPLORATION COMPLETED:

Landing Sites for the Last Missions

In July 1969 the Apollo Site Selection Board had compiled a list of 10 landing sites for Apollo 11-20, subject to further evaluation and revision in light of the results of early landings [see Chapter 10] [see Table 2]. In August and September, responding to a request from Headquarters and MSC program managers for detailed science mission plans, members of the Group for Lunar Exploration Planning and its Site Selection Subgroup, working with MSC operations planners and U.S. Geological Survey scientists, suggested some minor changes, based on a reevaluation of geologic features at one of the sites and the expected availability of good photography at another. These were endorsed by the Group for Lunar Exploration Planning on August 23.52

At the end of September, however, while many other complaints were being registered concerning Apollo [see Chapter 10], some members of the Science and Technology Advisory Panel and the lunar panel of the Lunar and Planetary Missions Board objected that their opinions were not receiving sufficient consideration in site selection. Harold Urey complained that he did not know who was making decisions regarding landing sites, nor what the reasons for choosing the various sites were: the correspondence he received was unintelligible, full of unexplained acronyms and couched in unreadable bureaucratic jargon. He could not take the time to attend meetings of the site selection subgroup to argue his case, however, because of academic commitments.53 Another meeting was held in mid- October in the hope of considering the advice of the objectors, but they were unable to attend. Gene Simmons, MSC's chief scientist, was annoyed and disappointed. He wrote to the chairman of the Science and Technology Advisory Committee,

To those of us who have been intimately involved with the scientific recommendations on Apollo sites for some time, it was particularly disappointing that only one of these "senior scientists" showed up in time for the meeting. . . . The entire decision-making process of NASA on the landing sites for the H and J series missions was postponed in order for these individuals to meet with us and provide the kind of counsel that only they, presumably, could give. . . . [Nonetheless,] we as a group felt that we should proceed with the reexamination of the proposed landing sites.54

The Site Selection Board, meeting at the end of October, discussed this list in light of the improvements (lunar roving vehicle and added payload) expected for the J missions. Marius Hills, Descartes, and Hadley appeared to present no problems of accessibility, but Copernicus and Tycho were only marginally acceptable. Marius Hills was accessible only during two summer months. Descartes, Hadley-Apennine, Davy Rille, and Censorinus were not adequately covered by available site photographs. MSC was prepared to accept the' available photographic coverage for Fra Mauro, Littrow, Marius Hills, Copernicus, and Hyginus, but planners would have to sacrifice some fidelity in terrain models for training. Tycho was discussed at some length. It was the most difficult site on the list to reach, but in many ways was scientifically attractive. Finally the board relegated Tycho to the last J mission, which would leave ample time to look for ways to overcome the operational limitations. Houston's representative proposed yet another sequence of missions [Table 4], which the board approved as a basis for continuing evaluation.56

Assignment of sites to specific missions was tentative at this stage of the project because the necessary information was still sketchy. By the end of 1969, however, much of this information was becoming available. Apollo 12 demonstrated the ability to make precision landings, a requirement for the later H missions. As the initial scientific study of samples from Apollo 11 and 12 yielded information on chemical composition and age, the basis for choice among the remaining sites became somewhat more clear-cut. On the other hand, in January 1970 Apollo 20 was canceled, and the prospect that others might be dropped clouded the picture.

In February 1970 the Group for Lunar Exploration Planning met at Houston to reassess the fist of sites in fight of recent developments and to make new recommendations to the Site Selection Board. Tycho was reluctantly dropped from consideration because of its operational problems, although the group indicated that location was still interesting. The remaining sites on the list approved in October were endorsed, with minor changes. Fra Mauro remained the highest priority on the list because it offered the chance to sample material that originated deep within the moon. The group wanted to move Marius Hills from the second to the first J mission, interchanging it with Descartes. It specified that the target on the fourth "H" mission should be as near the highland terrain around Davy Rille as possible, to be reasonably sure of sampling highland material; otherwise Censorinus was preferred. Finally, the group recommended that the site for the landing at Hadley (J-4) be moved from the west side of Hadley Rille to the east side, to allow the astronauts to reach the Apennine Front and sample more than one type of terrain.57

MSC's Science and Applications Directorate evaluated this list with three guiding principles in mind: information gained from previous missions should weigh heavily in selection of later sites; since only a few missions remained, sites should be chosen to answer as many scientific questions as possible and missions should have multiple objectives; and the sites of undisputed scientific interest should be scheduled as early as possible. On this basis, MSC recommended shifting Copernicus to Apollo 16 and the Marius Hills to Apollo 18. The objectives at the Marius Hills site might be satisfied at either Davy or Copernicus, and some of the instrumentation desired for a Marius Hills mission might not be developed in time to fly on Apollo 16. Should that be the case, a delay would imperil the sequence, because the useful payload for a Marius Hills mission fell off by as much as 6,000 pounds (2,720 kilograms) after midyear.* 58

After the Apollo 13 mission had to be aborted, the Group for Lunar Exploration Planning reconsidered its recommendations and endorsed Fra Mauro (the planned Apollo 13 site) for Apollo 14. Its importance in dating the Imbrian event remained, and it offered advantages for placement of another passive seismometer, an active seismometer, and a third laser retroreflector. For Apollo 15, the Group recommended a site near the Davy crater chain, assuming adequate photography could be obtained on 14.59

As it turned out, the photos from Apollo 14 would come too late to allow certification of Davy as a site for Apollo 15, and in June the site selection subgroup convened once more to evaluate candidate sites for Apollo 15 and 16. By that time it was already clear that more missions might be canceled, which further complicated the subgroup's deliberations. After a long discussion that reexamined 14 sites** for which reasonably adequate photographs were available, the subgroup agreed on a recommendation that the Marius Hills be the candidate for Apollo 15. Littrow was the chosen alternate. For Apollo 16, Descartes was the landing site of choice. In the event that Apollo 15 was canceled, Marius Hills should be shifted to Apollo 16 and Descartes to 17. The remaining sites were ruled out, either because MSC had determined that they were unsuitable for landing or because they appeared to offer insufficient new scientific information to justify consideration.60 Following this meeting only Littrow, Descartes, Hadley- Apennines, and the Marius Hills remained as strong candidates for the last missions.

In the next three months, MSC began to try to overcome the difficulties in getting a consensus on landing sites among the various scientific groups.*** Anthony Calio decided to ask three groups of scientists to examine the question separately and make independent recommendations. After receiving their opinions, Calio summarized the criteria for selection of an Apollo 15 site. It should offer a major advance in the study of the moon and a high probability of answering essential scientific questions and satisfying the objectives of more than one scientific discipline; it should be certifiable on the basis of existing photography and not dependent on photographs to be obtained by Apollo 14; it should be operationally feasible without further analysis; and it should be appropriate for either a walking mission or a rover mission, so that it could be flown on Apollo 15 or (if 15 should be canceled) 16. Calio then described the geologic features of the Hadley-Apennine site, located on the eastern rim of Palus Putredinus, nearly 30 degrees north of the moon's equator. Among the sites still under consideration, Hadley was unique in offering direct access, with or without a roving vehicle, to a mountainous highland, a mare surface, and a sinuous rille. Furthermore, it appeared on most of the priority lists produced by the disciplinary groups. It would offer the advantage of establishing the high-latitude arm of a well dispersed array of geophysical instruments, essential to investigating the moon's interior (by seismology) and its orbital librations (by measurements from the laser retroreflectors).61

After the cancellation of Apollo 15 and 19 in early September 1970, MSC presented the case for Hadley at the Apollo Site Selection Board's meeting later that month. Arguments for Hadley and Marius Hills were fairly evenly matched, both from scientific and operational standpoints, and the debate between the two was virtually deadlocked until astronaut David Scott, recently picked to command Apollo 15 (see below), said that he preferred Hadley although he thought he could land at either site. Scott's opinion tipped the balance. The Board recommended Hadley for a launch date between July and September 1971, Descartes for Apollo 16 between January and March 1972. The choice of a site for Apollo 17 was left open; Marius Hills and Copernicus were the leading candidates, but others (e.g., Littrow) were still in the running, and a new site might be found in future orbital photography.62

The September meeting wrapped up the Apollo Site Selection Board's unfinished business for the time being. After Apollo 14, scheduled for the following April, it would reconvene to examine the list of sites in light of the results of that mission.

* This was the result of the mission rule requiring daylight launches and of the annual variation in the geometric relationships of the earth, sun, and moon.

** Censorinus, Littrow, Alphonsus, Hyginus Rille, Rima Bode II, Hipparchus, Mosting C, Dionysius, Sinus Medii, Flamsteed IP, Gassendi, Copernicus, Descartes, and Marius Hills [see Table 1]. At this meeting, MSC ruled out Copernicus and Censorinus as unsuitable for landing because of rough terrain. The subgroup dropped Gassendi, which appeared to present the same disadvantage,

*** According to an MSC participant, consensus among the scientists at a site selection meeting was nearly impossible to obtain. Each individual repeatedly voted for the site of his choice, and in the end, NASA (i.e., MSC) had to made the decision. Brooks, Grimwood, and Swenson, Chariots for Apollo, p.365.

Table 2. Lunar landing site assignments.*

Mission    Site                   Mission    Site

  G-1      Site 2 (Tranquility)     J-1      Copernicus peaks
  H-1      Site 5 or 4 (Oceanus     J-2      Marius Hills
            Procellarum)
  H-2      Fra Mauro                J-3      Tycho
  H-3      Rima Bode II             J-4      Rima Prinz I
  H-4      Censorinus               J-5      Descartes

*Recommended by the Group for Lunar Exploration Planning; minutes of Apollo Site Selection Board Meeting, July 10, 1969.

Mission    Prime Site    Alternate 1   Alternate 2   Alternate 3

H-2 (13)   Fra Mauro     Alphonsus**   Alphonsus**   Fra Mauro**
H-3 (14)   Littrow       Littrow       Littrow       Littrow
H-4 (15)   Censorinus    Fra Mauro     Fra Mauro     Censorinus
J-1 (16)   Descartes     Censorinus    Censorinus    Descartes
J-2 (17)   Marius Hills  Marius Hills  Marius Hills  Marius Hills
J-3 (18)   Copernicus    Copernicus    Davy Rille    Davy Rille
J-4 (19)   Hadley        Hadley        Hadley Rille  Hadley Rille
J-5 (20)   Tycho         Tycho         Copernicus    Copernicus

Table 4. Sites recommended MSC.*

Mission    Prime Site    First launch    Alternate site
                         opportunity

H-2 (13)   Fra Mauro     Mar. 12, 1970   Hyginus
H-3 (14)   Littrow       July  8, 1970   Littrow
H-4 (15)   Censorinus    Oct. 30, 1970   Fra Mauro
J-1 (16)   Descartes     Mar. 29, 1971   Censorinus
J-2 (17)   Marius Hills  July 30, 1971   Marius Hills
J-3 (18)   Copernicus    Feb. 19, 1972   Davy Rille
J-4 (19)   Hadley        July 14, 1972   Hadley
J-5 (20)   Tycho         Feb.  7, 1973   Copernicus

*Minutes, Apollo Site Selection Board Meeting, October 30, 1969.

51. Richard G. Smith, MSFC, to Petrone, "Use of 510 Launch Vehicle for 107,000 Pounds Payload Mission," July 22, 1970.

52. Scherer, "Minutes of the Apollo Site Selection Board Meeting, Oct. 30, 1969"; Farouk El-Baz and D. B. James, "Minutes of the August 12-14 Meeting of an Ad Hoc Working Group on the Science Objectives of Apollo Missions 12-20," Bellcomm Memo for File, Aug. 18, 1969.

53. Gene Simmons to Dr. Charles H. Townes and Dr. John Findlay, Oct. 21, 1969; Urey to Townes and Findlay, Oct. 27, 1969. Urey felt unable to attend more meetings because "I shall miss three classes this quarter in my thermodynamics course - one to attend the Flagstaff [site evaluation] meeting and two to collect medal awards. . . . I cannot serve on more committees and do my university work."

54. Simmons to Townes and Findlay, Oct. 21, 1969.

55. Scherer, "Minutes of the Apollo Site Selection Board Meeting, Oct. 30, 1969."

56. Ibid.

57. "Group for Lunar Exploration Planning, Minutes of Meeting, February 6-7, 1970"; A. J. Calio to Mgr., Apollo Spacecraft Program, "Site Selections for the Remaining Apollo missions," Mar. 24, 1970.

58. Calio to Mgr., Apollo Spacecraft Program, "Site Selections for the Remaining Apollo missions," Mar. 24, 1970.

59. Idem, "Site Selections for Apollo missions 14 and 15," May 6, 1970.

60. Ronald L. Berry to Chief, Lunar Mission Analysis Branch, "Results of the Sub-GLEP Apollo Site Selection Meeting on June 5, 1970," June 17, 1970; Hinners to multiple addressees, "Subgroup Meeting of June 5, 1970," June 10, 1970.

61. Minutes of the Apollo Site Selection Board Meeting, Sept. 24, 1970; Calio to Mgr., Apollo Spacecraft Program, "Landing Site Recommendation for Apollo 15 Mission," Aug. 17, 1970.

62. Berry to multiple addressees, "Results of the Apollo Lunar Landing Site Selection Board Meeting of September 24, 1970," Sept. 30, 1970; Minutes of the Apollo Site Selection Board Meeting, Sept. 24, 1970.