On July 18, 1969, MSC issued the mission requirements document for Apollo 12, listing the primary purposes of the mission as investigating the lunar surface environment, emplacing the first Apollo lunar surface experiments package (ALSEP), obtaining samples from a second lunar mare, and enhancing the capability for manned lunar exploration. Major changes from Apollo 11 included the possible use of a hybrid trajectory* rather than a free-return trajectory and scheduling two periods of lunar surface exploration by both crewmen. Five possible landing sites were specified, including site 5 (the western mare site preferred by the scientists) and Surveyor III.46
After Sam Phillips designated the Surveyor as the spot for Apollo 12 to land, mission planning focused on the problems of precision landing (see above), deployment of the ALSEP, geological observations and sample collection, and examination of the Surveyor and its surroundings.47 Although some at MSC believed that returning some components of the Surveyor was of considerable importance, other surface activities were given higher priority48 - probably in deference to the scientists. (The site had been unanimously rejected by the Group for Lunar Exploration Planning, who considered the inert spacecraft to be an "attractive nuisance" that would likely divert the astronauts from more important work.49) Deployment of the first ALSEP was high on the priority list, since scientists had been disgruntled by the decision to fly a simplified package of surface instruments on Apollo 11. [see Chapter 8] Geologists wanted the Apollo 12 astronauts to be somewhat more selective than their predecessors in collecting samples and stressed the importance of documenting (photographing and describing) them. They also preferred more rocks and less dust, if possible. To determine what the astronauts should do on and around Surveyor III, MSC had already begun discussions with Hughes Aircraft Company.
* Hybrid trajectories were fuel-saving flight paths which, unlike free-return trajectories, would not return the spacecraft to earth if the service module's main propulsion system failed to put it into lunar orbit. They were designed so that in case of such a failure the lunar module's descent engine could correct the resulting flight path (which might put the spacecraft with its three occupants into solar orbit) for return to earth.
46. MSC, "Mission Requirements, SA-507/CSM-l08/LM-6, H-1 Type Mission, Lunar Landing," MSC SPD9-R-051, July 18, 1969, pp. 2-1 to 2-3.
47. MSC, Apollo 12 Mission Reviews, Aug. 15 and Oct. 2, 1969.
48. Andre J. Meyer to PA/Mgr., Apollo Spacecraft Program, "Surveyor 3 Activities on Apollo 12 Mission," Aug.28, 1969.
49. Hinners to L. R. Scherer, "Second Mission Landing Sites," June 18, 1969; James H. Sasser to multiple addressees, "Highlights of GLEP Site Selection Subgroup Meeting in the Mapping Sciences Laboratory on June 17, 1969," June 22, 1969.