Free Astronomy Magazine May-June 2019

33 MAY-JUNE 2019 ASTRONAUTICS because of the unpleasant proxim- ity of a crater. Although a number of strategic sites were identified near ALS-5, they were rather insignificant. A site in the large crater Hipparchus was considered insufficiently docu- mented. The corrugated terrain north of the Fra Mauro crater was rejected as too demanding. The re- laxation of the operational con- straints made it possible to restore ALS-6. This was in the Flamsteed Ring, the big crater almost com- pletely flooded by a lava flow from Oceanus Procellarum. Moreover, the fact that ALS-6 was not far from where Surveyor 1 had landed prompted the flight dynam- Nevertheless, this program was so focused on locating open sites for the first landing that the coverage of more difficult sites was too su- perficial to be certified. It was clear, therefore, that if Apollo had ex- ploited the relaxation of the flight dynamics constraints, the early mis- sions would have to search out-of- area sites for their successors. Once the accuracy of the location had been demonstrated, it would have been possible to assign more specific targets rather than generic areas. Apollo 12 had to open this door. The choice of ALS-7 for Apollo 12 would allow it to scour Fra Mauro, the region of Descartes and Davy Rille, a chain of craters ics team to propose it as a destina- tion because positioning at a short distance from another spacecraft would have been a powerful demonstration of precision. Unfortunately, since this site was so west, it had no backup site. But there was another spacecraft in the eastern part of Oceanus Procel- larum that could have easily repre- sented a backup to the west. It was a site selected for Surveyor 3, then discarded because it was too rough for Apollo, but eventually renamed ALS-7. In addition to exploring the most favorable sites for the first landing of Apollo, the Lunar Or- biter photographed many charac- teristic sites. A POLLO 14 − View from west of the lunar module looking east. [NASA, Project Apollo Archive]