DESTINATION MOON: A History of the Lunar Orbiter Program
Developing Mission Designs
[183] While Bellcomm was advising OMSF, the Langley Lunar Orbiter Project Office carefully studied and compared the proposed missions that Bellcomm had developed (i.e., in the Lloyd-Fudali report) with the one developed by Boeing. Thomas Young of the Langley LOPO informed Norman L. Crabill on May 7 of the conclusions pertaining to the reliability of each proposed mission. His memorandum stressed the differences in reliability in the studies performed by Bellcomm and Boeing. The Bellcomm mission required 4.5 days longer to accomplish than did that of Boeing, but the variation in resulting data was minimal.10
Young's LOPO mission planning study group continued to analyze Lunar Orbiter capabilities and concluded in a report to Crabill on June 14 that Apollo and Surveyor requirements permitted variable Lunar Orbiter missions, ranging from a concentrated to a distributed photographic mission, depending upon primary requirements for the two programs. For photographic missions with sites distributed within the Apollo zone, a set of trajectories could be defined that were generally independent of the exact locations of the sites. They could be planned by placing mild [184] restrictions on the latitude range of the sites. Thus, for Missions I, II, and III (with prime sites in the Apollo zone), trajectories could be defined without consideration of the exact site locations. Mission II sites were to be selected from the review of the results of secondary sites of Mission I. and Mission III sites were selected from all results of the first two missions.11 However, the Langley Project Office considered the establishment of mission objectives a prerequisite to further mission planning.12
On Friday, June 25, representatives from OSSA, OMSF, the Langley Lunar Orbiter Project Office, the Manned Space Flight Center, the Jet Propulsion Laboratory, and Bellcomm held the initial coordination meeting to establish a preliminary plan for utilizing Lunar Orbiter's mission capabilities with the first Lunar Orbiter mission, the first Surveyor mission, and with Apollo mission requirements. During the meeting it was agreed that the Lunar Orbiter could best aid Surveyor by screening sites and defining targets which had a high probability of being smooth. The [185] representatives from the Apollo Systems Engineering Office stated that Lunar Orbiter could photograph a landed Surveyor spacecraft from an altitude of 46 kilometers with I-meter resolution because of the Surveyor's shadow at a prescribed Sun angle and the high albedo of the spacecraft. Lunar Orbiter had originally been targeted to screen Surveyor sites. After a Surveyor had successfully landed, the Orbiter was to overfly it and photograph it through the 610 mm high-resolution camera lens. The increased capabilities of the Lunar Orbiter photo subsystem now allowed it to combine screening and overfly tasks in the high-resolution mode.13
The Apollo Systems Engineering Office and the Manned Space Flight Center preferred that Lunar Orbiter fly a distributed mission; this offered a sampling technique better able to find an area suitable for an Apollo landing, to define suitable areas for further coverage on later Orbiter flights, and to increase the flexibility of the Apollo launch window by finding suitable sites spread across the Apollo zone of interest. Both the Manned Space Flight Center and Bellcomm recommended that Lunar Orbiter photograph the Ranger VIII impact point located in the Apollo zone because possibly it could serve as a future [186] Apollo orbit anchor point.14
The June 25 Langley meeting provided the Lunar Orbiter Project Office with information concerning mission objectives from the Apollo and the Surveyor Program Offices. This assisted Langley in its mission planning activities, and it, in turn, was better able to guide the Boeing Company in its work.15 Moreover, the meeting produced the basis for efficient coordination between the NASA offices requiring Lunar Orbiter data and enabled the Lunar Orbiter Program to develop preliminary mission plans.16
From July 13 to 15 a preliminary mission definition meeting for Lunar Orbiter convened at Langley. The men present17 defined preliminary mission types on the basis of decisions arising out of the June 25 meeting at Langley. These mission types depended upon three basic flight objectives: 1) gathering significant topographic information of the Moon's surface for selection of Surveyor, and Apollo [187] sites; 2) providing selenodetic data on the size, shape, and gravitational properties of the Moon necessary for determining orbit lifetime of a Lunar Orbiter sufficiently long to allow adequate time for readout; and 3) providing measurements of micrometeoroid and radiation flux in the lunar environment.18
By the end of July the Lunar Orbiter Program Office in Washington had the results of the Langley LOPO and Bellcomm preliminary mission studies. Four mission types had been formulated on the basis of requirements and recommendations from Apollo, Surveyor, and Lunar Orbiter Program Offices. Briefly summarized they were:
Type I -Site sampling, a distributed mission allowing eleven single passes over different terrains (i.e., highlands, maria, rilles).
Type II -wide-area coverage for Surveyor of only three separate sites.
Type III -Surveyor location mission to pinpoint landed Surveyor at one-meter resolution.
Type IV -a combination million for more sophisticated work later in the program.19
A joint OSSA/OMSF Site Survey Meeting was held at NASA Headquarters on August 4 to review the status of the Surveyor, Lunar Orbiter, and Apollo Programs and to discuss [188] preliminary mission planning for Lunar Orbiter and selection of Surveyor landing sites. Clifford H. Nelson, Lunar Orbiter Project Manager, summarized the status of the Lunar Orbiter Program and pointed out that the program expected to meet its original launch schedule but that slips in subsystems, especially the photographic subsystem, had necessitated further compression of the testing schedule in order to hold the launch schedule.20
After Nelson's report and the Apollo status report., Norman L. Crabill presented the preliminary planning for the first two Lunar Orbiter mission types. He outlined the ground rules for the Type I mission:
Ground Rules
1) Photograph two sites of each smooth-looking-terrain class up to a total of eleven sites within the Apollo area of interest.
2) Photograph Ranger VIII and any landed Surveyors.
3) Photograph each site using a single pass with sixteen contiguous I-meter-resolution frames per pass.
4) Read out up to four frames between passes.
5) Define mission for the Boeing Company by the fall of 1965.
And for the Type II mission:
1) Topography mapping for possible Surveyor sites.
2) [189] High-precision selenodetic data.
3) Lunar environmental data.
Ground Rules
1) Photograph three sites spread 30° of longitude apart.
2) Use four passes per site.
3) Use sixteen high-resolution contiguous frames per pass.21
At the August 4 meeting Lee R. Scherer proposed the establishment of a Lunar Photographic Analysis Steering Group which would act as a sounding board for suggestions and requests from the various programs involved in lunar exploration. It would also establish priorities and serve as coordinator for NASA-wide activities related to obtaining photographic data of the Moon. The group could coordinate such activities as control of Earth-based lunar mapping, direction and planning in the analysis of Lunar Orbiter data, monitoring of pertinent work for other government agencies, planning with the OSSA planetology group, handling agreements for data processing priorities, and coordinating Apollo needs with other requirements. No final action was taken on Scherer's proposal at the meeting, but it stimulated discussion on these aspects of mission planning and data utilization.22