DESTINATION MOON: A History of the Lunar Orbiter Program
Apollo Mission Planning and Lunar Orbiter Data
[308] The Apollo Program was the primary user of Lunar Orbiter data in the months following each Orbiter mission and in the period between the final mission and the first manned landing on the Moon in 1969. The story behind the Apollo site selection activities is beyond the scope of this history, but a brief summary of Lunar Orbiter's part in Apollo mission planning will demonstrate the role that [309] the Lunar Orbiter Program played in the Apollo Program as a result of cooperation between the Office of Space Science and Applications and the Office of Manned Space Flight.
The Apollo Site Selection Board (ASSB) had begun its work at its first meeting on March 16, 1966. No Lunar Orbiter or Surveyor spacecraft had yet flown, and therefore, all discussion of site selection requirements had depended upon Ranger and Earth-based telescopic photography. Lunar Orbiter would soon change Apollo Program thinking about landing sites. At the first ASSB meeting the members identified a number of potential sites with the expectation that the sites finally chosen would be among them.12
By the following ASSB meeting Surveyor I had successfully landed on the Moon in Oceanus Procellarum, north of the crater Flamsteed. The first Lunar Orbiter mission, scheduled for early August, would attempt to photograph the Surveyor. Lunar Orbiter Program officials would adjust the positions of sites A-9 and A-10 to combine two blocks of photography for greater surface coverage of the area in which the unmanned spacecraft had touched down. In addition to this change in the first Lunar Orbiter missions Norman Crabill and Thomas Young of the Lunar Orbiter Project Office, Langley, on June 1 [310] presented the ASSB meeting recommendations for Lunar Orbiter Mission B. They believed that each Mission B site contained areas smooth enough to qualify as candidate Apollo sites. Finally the Apollo Program representatives, after reviewing the target sites for Lunar Orbiter Missions A and B. concluded that these sites would satisfy all known requirements for the Apollo missions if the surface of the Moon proved hospitable at each one.13
At the June 1 meeting Oran W. Nicks of OSSA asked Apollo Program people if they had any requirements for lunar landmarks which Orbiter could photograph. Owen E. Maynard of the Manned Spacecraft Center, who had presented the Apollo Site Selection Plan to the meeting, replied that the program had no plan at the time to use landmarks for updating orbits of the Apollo spacecraft. However, it would be desirable if such landmark sites could be located within a block of Orbiter photography containing a proposed Apollo landing site.14
By the December 15 ASSB meeting Lunar Orbiter I had obtained medium-resolution stereo photography of nine potential Apollo landing sites. Lunar Orbiter II had photographed thirteen potential sites in medium-resolution [311] stereo and high-resolution monoscopic photography. Lawrence Rowan of the United States Geological Survey interpreted to those present the data of the lunar surface with respect to impact craters, volcanic fields, and mass wasting of the top layer of the Moon's soil. He made the following points in his talk:
1. Older mare areas such as those in Lunar Orbiter II photographs of Site II P-6 do not have the problem of crusts and lava tubes as young areas such as Site II P-2 most likely have.
2. Surveyor I photographs in Oceanus Procellarum exhibit more surface rocks than are found in Sinus Medii and Mare Tranquillitatis, suggesting that it might be younger and have a thin surface layer.
3. Slopes in older highland and smoothed mare craters, which show "patterned grounds" may be unstable, with collapse or landslide dangers.15
Analysts for the Lunar Orbiter and Apollo Programs had chosen nine sites from Lunar Orbiter I photography and had applied Apollo site selection criteria in the effort to find Lunar Module landing areas. The December 15 ASSB meeting reviewed the results. Twenty-three areas proved large enough to contain a landing ellipse. These were undergoing further study, [312] and Apollo Program personnel evaluating them would make detailed crater counts of each during the next stage of selection. Following the preliminary analysis eight of the twenty-three areas merited special study.16 The process of screening the Lunar Orbiter data is given in the diagram on the next page.
Landing site data determined from further analyses of Orbiter photography brought more confirmation that the Lunar Module design was correct and offered sufficient capability to land on the Moon. At a March 30, 1967, meeting of the ASSB, Donald C. Cheatham from the Manned Spacecraft Center pointed out that "the LM redesignation capability permits a change of touchdown point of 10,000 feet crosstrack at high gate (90 feet per second delta V. command at 30,000 feet down range). Visibility restrictions do not permit uprange redesignation. Preliminary examination of the Lunar Orbiter photography indicate that this capability will be sufficient for crater avoidance."17 Already Lunar Orbiter had told Apollo mission planners much about the areas where they could and could not send a Lunar Module.

313] (DIAGRAM)

[314] Finally, the December 15, 1967, meeting of the ASSB at Houston had the photographic data of all five Lunar Orbiters upon which to base its judgments. The major criteria for selection of the landing sites subsequently depended upon performance constraints of the Apollo spacecraft, particularly the Lunar Module.18 Lunar Orbiter had provided the photographic data which the Apollo Program had originally requested. Surveyor data continued to come in from three landed spacecraft in the Apollo zone of interest. Two more Surveyors would land in different areas of the Moon before that program concluded operations. Beyond this Lunar Orbiter photography did not constitute a major basis for the final selection of Apollo landing sites. Selection had to depend upon performance constraints of the Lunar Module. At this point Lunar Orbiter had fulfilled its primary mission for the Apollo Manned Lunar Landing Program.
A year later, after the first Apollo mission to orbit the Moon, Apollo 8 Astronaut James A. Lovell, Jr., reported:
. . . . the Lunar Orbiter photographs which we had on board were quite adequate. There was no problem at all in determining objects, particularly on the near side of the moon. There are suitable landing sites. They are very easily distinguished. We could pick them up. We could work our way in . . . . The Lunar Orbiter photos again were helpful . . . to check the craters on the back side.19