DESTINATION MOON: A History of the Lunar Orbiter Program
 
 
CHAPTER X: MISSIONS IV AND V: THE LUNAR SURFACE EXPLORED
 
Preparations for the Fifth Mission
 
 
 
[284] In March 1967, before the fourth mission, a working group within the Lunar Orbiter Program developed tentative objectives for the fifth and final mission. These called for a multi-site scientific mission with the capability of reexamining the eastern Apollo sites. A subgroup formed to determine specific target sites for the photographic mission of the last flight. As in the past the Lunar Orbiter Project Office at Langley coordinated all mission planning activities.27 On March 21 the entire working group met at Langley to review the preliminary plans. The results of the review were sent to Boeing for further consideration before a presentation to the Ad Hoc Surveyor/Orbiter Utilization [285] Committee at the end of the month.
 
The Lunar Orbiter Mission V Planning Group, which had come into being in March, met at the Jet Propulsion Laboratory on May 26 to review the Boeing Company's preliminary mission design for the fifth Orbiter. Of special interest was the problem of orbit design. The Group worked out an orbit design which would meet the needs of the multi-site mission without violating spacecraft design restrictions. The orbit would have an inclination of 85° to the Moon's equator. The perilune altitude would be low enough to allow two-meter-resolution photography on vertical photographs instead of one-meter, in order to obtain more useful convergent stereo photography at the higher altitude of 100 kilometers. At the higher perilune the cross-camera tilt would be reduced, offering better resolution on the convergent stereo photographs. At the same time, increasing the perilune altitude broadened the coverage of the science sites.28
 
The Planning Group decided to keep the Lunar Orbiter V apolune as low as possible and no higher than 1,500 kilometers above the Moon. Lighting angles from the morning terminator would range from 8° to 24°-angles offering the greatest potential relief rendition of surface features [286] to assist scientists in analyzing topographic and geologic aspects of the lunar surface.29
 
By June 14 the Lunar Orbiter Program Office had the completed plan for the fifth mission, and the Ad Hoc Surveyor/Orbiter Utilization Committee approved it on the same day. As a result of the review of Lunar Orbiter IV photography, mission planners at Langley changed almost 50% of the sites they had initially selected for the fifth mission.30