-
DESTINATION MOON: A History of the
Lunar Orbiter Program
-
-
- CHAPTER VIII: LUNAR ORBITER
MISSION OBJECTIVES AND APOLLO REQUIREMENTS
-
- 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.
-
-