DESTINATION MOON: A History of the Lunar Orbiter Program
The Ad Hoc Surveyor/Orbiter Utilization Committee (SOUC)
[190] All of the previously discussed plenary meetings served as the basis for setting up the OSSAIOMSF Ad Hoc Surveyor/Orbiter Utilization Committee, which held its first meeting on August 20, 1965.23 At this time Scherer reviewed the Lunar Orbiter photographic format and described the photographic subsystem in detail. Following this he stressed these major points which had to be considered in Orbiter mission planning:
1) Resolution and area coverage are directly proportional to orbital altitude.
2) A photographic pass requires an altitude manuever.
3) The system can take 1, 4, 8, or 16 pictures on a single pass.
4) The system is capable of taking 192 pictures total.
5) The last 4 pictures in the take-up spool can be read out on command anytime during the mission.
6) The system is capable of reading out one frame during each orbit. Pictures cannot be taken during the readout.
7) The thread-up distance from the camera to the readout is 18 frames.
8) Total readout will be accomplished after completion of all photography; the last photograph taken will be the first read out.
9) [191] Gravity perturbations and latitude width of good lighting both increase with orbital inclination. There will have to be some trade-off studies made in this area; what's good for selenodesy doesn't produce the best pictures.24
Norman L. Crabill followed Scherer with an updated outline of the four mission types which Langley had developed for Lunar Orbiter:
Type I -- Photographs ten evenly distributed target sites in the Apollo zone of interest and covers each site in high- and low-resolution stereo photography (1 meter and 8 meters).
Type II -- Photographs four sites to screen for Surveyor landing sites in Apollo zone.
Type III -- Photographs to 1-meter resolution an area containing a landed Surveyor to learn as much as possible about the surrounding terrain,
Type IV -- Obtains a variety of topographic data not obtained by other mission types.25
The ordering of these mission types reflected the conservative philosophy of OSSA and Langley covering the Lunar Orbiter mission objectives. It was vital to obtain reliable, accurate data for the Apollo Program before attempting to do anything else. Thus the first mission type was entirely devoted to Apollo's needs. Also, the mission planners had to take into consideration the [192] possibility of a spacecraft or mission failure, in which case they wanted to have as many remaining Orbiters to carry out the Apollo photographic reconnaissance mission as possible. Were the Lunar Orbiter Program strictly pursuing scientific objectives unrelated to Apollo, a general survey mission of the entire Moon from a high polar orbit would have been preferable as the first mission. This was not the case.26
The SOUC agreed to let Scherer define the decisions and the dates for the next meeting. The Committee requested him to tell Boeing to concentrate on studies of multiple and distributed targets instead of studying models for large block photography of the Moon's surface. The Committee also asked Scherer to hold a working meeting of representatives from the Apollo, Surveyor, and Lunar Orbiter Programs to determine the preliminary plan for the first Lunar Orbiter mission. The Committee favored a distributed Type I mission and asked that a presentation of the first mission plan be made within thirty to forty-five days.27
The prime role in mission planning was carried out by [193] the Langley Research Center while the SOUC acted in an advisory way, coordinating activities among the various centers connected with the Lunar Orbiter Program. The working meeting requested by SOUC took place at Langley on September 8 and 9. It had the following major objectives:
1) To gain understanding of Orbiter and Surveyor mission design problems.
2) To review available data on the lunar surface.
3) To produce lists of lunar sites which would satisfy Apollo , Surveyor, and Lunar Orbiter constraints.28
At the meeting Scherer pointed out that Homer E. Newell, NASA Associate Administrator for Space Science and Applications, would have to make the final decision on the first mission plan for Lunar Orbiter and that he would rely on recommendations from Langley and SOUC. Therefore, the Lunar Orbiter Program Office would be required to present a detailed, well-defined plan to the Surveyor/Orbiter Utilization Committee.29
The Apollo Spacecraft Program Office (ASPO), represented by James Sasser from the Manned Space Flight Center, Houston, Texas.. expressed its desire for a Lunar Orbiter distributed mission and concurred on the sampling of [194] different terrain types within the Apollo zone of interest with emphasis on the areas of greatest apparent smoothness. However, ASPO did not want the lunar Orbiter restricted to sampling Surveyor-size landing areas or sites accessible only to the Surveyor spacecraft. As a result Sasser accepted an action item to provide the Lunar Orbiter Project Office with a letter confirming the bounds of the Apollo zone of interest.30
Lawrence Rowan of the United States Geological Survey made a presentation to the members of the meeting in which he discussed the USGS lunar terrain analysis based upon the newest lunar map from the Aeronautical Chart and Information Center (ACIC) with a scale of 1:1.000,000. Rowan talked about the various sources of data that went into making the lunar map and then gave an interpretation of terrain types on the Moon. The USGS terrain analysis enabled Rowan to present a list of nine terrain types to be sampled photographically by Lunar Orbiter: 1) dark mares 2) mare, 3) mare ridges, 4) mare rays 5) upland Unit-I, 6) deformed crater floors, 7) upland Unit-II, 8) crater rims, and 9) sculptured highlands.31 Rowan's information formed part of the basis for the site selection process which followed.
[195] The members of the meeting subsequently developed two Orbiter missions based upon the USGS terrain map and the following assumptions: 1) orbital inclination of spacecraft equals 12.5°, 2) descending-node photography to be employed, 3) orbital spacing to be based on Goudas's model of the Moon, 4) lighting band to be based on a spherical Moon, and 5) lighting band to be initially centered about the lunar equator at 0° longitude.32
Two preliminary mission plans resulted. Members at the meeting subsequently picked them apart and criticized various aspects. Their major criticism was that the plans included too many samples of mare terrain types. They generally agreed that on the first mission Lunar Orbiter should photograph only the Apollo zone of interest unless a Surveyor landed outside of it.33 The results of the Langley meeting formed the foundation of the Lunar Orbiter Mission A plan.