[edit] 1.0 Summary

Apollo 17, the final Apollo mission, was launched at 05:33:00 G.m.t. (12:33:00 a.m. e.s.t.), December 7, 1972, from Launch Complex 39 at the Kennedy Space Center. The spacecraft was manned by Captain Eugene A. Cernan, Commander; Commander Ronald E. Evans, Command Module Pilot; and Dr. Harrison H. Schmitt, Lunar Module Pilot.

The launch countdown had proceeded smoothly until T minus 30 seconds, at which time a failure in the automatic countdown sequencer occurred and caused a launch delay of 2 hours and 40 minutes. This was the only launch delay in the Apollo program that was caused by hardware failure. As a result, the launch azimuth was adjusted and an earth parking orbit of 92.5-miles by 91.2-miles was achieved. The vehicle remained in earth orbit for approximately 3 hours before the translunar injection maneuver was initiated. The translunar coast time was shortened to compensate for the launch delay. Transposition, docking, and lunar module ejection were normal. The S-IVB stage was maneuvered for lunar impact, which occurred about 84 miles from the pre-planned point. The impact was recorded by the Apollo 12, 14, 15, and 16 passive seismometers.

The crew performed a heat flow and convection demonstration and an Apollo light flash experiment during the translunar coast period. One midcourse correction was performed to achieve the desired altitude of closest approach to the lunar surface. The scientific instrument module door was jettisoned approximately 4 1/2 hours prior to lunar orbit insertion. The Apollo 17 spacecraft initiated the lunar orbit insertion maneuver and entered into a 170-mile by 52.6-mile orbit. Approximately 4 1/2 hours later, the command and service module performed the first of two descent orbit insertion maneuvers lowering the orbit to 59 by 14.5-miles. The command and service module and lunar module stayed in this orbit about 17 1/4 hours before undocking and separating. After undocking, the command and service module orbit was circularized to 70 miles by 54 miles and the lunar module lowered its orbit to 59.6-miles by 6.2-miles by performing the second descent orbit insertion maneuver. From this orbit, the lunar module initiated its powered descent and landed at 20 degrees 9 minutes 55 seconds north latitude, 30 degrees 45 minutes 57 seconds east longitude at 110:21:58.

The first extravehicular activity began at about 114:22. The offloading of the lunar roving vehicle and unstowage of equipment proceeded normally. The lunar surface experiment package was deployed approximately 185 meters west northwest of the lunar module. The Commander- drove the rover to the experiments package deployment site and drilled the heat flow and deep core holes and emplaced the neutron probe experiment. Two geologic units were sampled, two explosive packages were deployed and seven traverse gravimeter measurements were taken during the extravehicular activity. About 31 pounds of samples were collected during the 7 hour and 12 minute extravehicular activity.

The second extravehicular activity began at about 137:5. The traverse was conducted with real-time modifications to station stop times because of geological interests. Orange soil was found and has been the subject of considerable geological discussion. Five surface samples and a double-core sample were taken at this site. Three explosive packages were deployed, seven traverse gravimeter measurements were taken, and all observations were photographed. The crew traveled 7370 meters away from the lunar module, and this is the greatest radial distance any crew has traveled away from the lunar module on the lunar surface. About 75 pounds of samples were gathered during the 7 hours 37 minutes of extravehicular activity.

The third extravehicular activity began at about 160:53. Specific sampling objectives were accomplished at stations 6 and 7 among some 3-to 4-meter boulders. Nine traverse gravimeter measurements were made. The surface electrical properties experiment was terminated because the receiver temperature was approaching the upper limits of the data tape and the recorder was removed at station 9.

At the completion of the traverse, the crew selected a breccia rock, which was dedicated to nations represented by students visiting the Mission Control Center. A plaque on the landing gear of the lunar module commemorating all Apollo lunar landings vas then unveiled. Samples amounting to about 137 pounds were obtained during the 7-hour and 15-minute third extravehicular activity for a total of approximately 243 pounds for the mission. The lunar roving vehicle was driven about 36 kilometers during the three extravehicular activities. The total time of the three extravehicular activities was 22 hours and 04 minutes.

Numerous orbital science activities were conducted in lunar orbit while the lunar surface was being explored. In addition to the panoramic camera, the mapping camera, and the laser altimeter, three new scientific instrument module experiments were included in the Apollo 17 complement of orbital science equipment. An ultraviolet spectrometer measured lunar atmospheric density and composition, an infrared radiometer mapped the thermal characteristics of the moon, and a lunar sounder acquired data on subsurface structure. The orbital science experiments and cameras have provided a large amount of data for evaluating and analyzing the lunar surface and the lunar environment.

The command and service module orbit did not decay as predicted while the lunar module was on the lunar surface. Consequently, a small orbital trim maneuver was performed to laver the orbit, and in addition, a planned plane change maneuver was made in preparation for rendezvous.

Lunar ascent vas initiated after 74 hours 59 minutes and 39 seconds on the lunar surface, and vas followed by a normal rendezvous and docking. Samples and equipment were transferred from the ascent stage to the command module, and the ascent stage was jettisoned for the deorbit firing. The ascent stage impacted the lunar surface at 19 degrees 57 minutes 58 seconds and 30 degrees 29 minutes 23 seconds about a mile from the planned target. An additional day was spent in lunar orbit performing scientific experiments, after which transearth injection was initiated.

A 1-hour and 6-minute transearth extravehicular activity vas conducted by the Command Module Pilot to retrieve the film cassettes from the scientific instrument module bay. The crew performed the Apollo light flash experiment and operated the infrared radiometer and ultraviolet spectrometer during the transearth phase. One midcourse correction was performed during this phase.

Entry and landing were normal. The command module landed in the Pacific Ocean vest of Hawaii, about 1 mile from the planned location. The Apollo 17 mission lasted 301 hours, 51 minutes, and 59 seconds. The Apollo 17 mission thus brought to a close the Apollo Program, one of the most ambitious and successful endeavors of man.

[edit] 2.0 Introduction

The Apollo 17 mission was the final mission in the Apollo program. The mission accomplished the sixth lunar landing and also completed the series of three orbital-science-oriented missions.

The Lunar Module Pilot was the first Scientist-Astronaut assigned to an American manned spaceflight mission. His academic background includes a Doctorate in Geology, and he has participated in many unique geological activities. He was selected as a Scientist-Astronaut in June, 1965, and this was followed by a year of flight training. His first mission assignment was as the backup Lunar Module Pilot for Apollo 15. la 1972, he was assigned as the prime Lunar Module Pilot for the Apollo 17 mission.

The vehicle configuration was similar to those of Apollo 15 and 16. There were significant differences in the science payload for Apollo 17. Spacecraft hardware differences and experiment equipment are described in Appendix A. The mission achieved a landing in the Taurus-Littrow region of the moon and returned samples of the pre-Imbrium highlands and young craters. An assessment of the mission objectives is presented in section 13.

This report primarily provides information of the operational and engineering aspects of the mission. Preliminary scientific results and launch vehicle performance are reported in references 1 and 2, respectively. A complete analysis of all applicable data is not possible within the time frame of the preparation of this report. Therefore, report supplements will be published as necessary. Appendix E lists the reports and gives their status, either published or in preparation. Standard English units of measurement are used in those sections of the report pertaining to spacecraft systems and trajectories. The International System of Units (SI) is used in sections pertaining to science activities. Unless otherwise specified, time is expressed as elapsed time from range zero (established as the integral second before lift-off), and does not reflect the time update shown in table 3-I. Mileage is given in nautical miles and weight is referenced to earth gravity.

[edit] 3.0 Trajectory

The basic trajectory profile for this mission was similar to that planned for the Apollo 16 mission. The major differences, aside from those required to reach the Taurus-Littrow landing site, were those required because of a night launch, translunar injection being initiated over the Atlantic Ocean rather than the Pacific Ocean, descent orbit insertion being performed in two maneuvers rather than one, and the elimination of the orbit shaping maneuver and the satellite jettisoning event. The sequence and definition of events for the Apollo 17 mission are shown in tables 3-I and 3-II. Tables 3-III and 3-IV contain the listing and definition of trajectory parameters, and table 3-V contains a summary of the maneuvers.

[edit] 3.1 Launch and translunar trajectories

The launch trajectory is presented in reference 3. The launch azimuth was updated from 72 degrees east of north to 91 degrees 30 minutes east of north. The translunar injection differed from the original plan because of a 2-hour 40-minute launch delay. This delay resulted in the translunar coast time being shortened (accomplished automatically by the launch vehicle guidance system), so that the arrival time at the moon would remain the same as that planned prelaunch. This constant time of arrival plan simplified the crew training by providing them with only one lunar lighting condition and one set of lunar groundtracks with which they had to become familiar, resulting in a single set of conditions on which the crew could concentrate their training.

One translunar midcourse correction of 10.5 ft/sec was required and performed at the second option point. The scientific instrument module door was jettisoned about 4 1/2 hours prior to lunar orbit insertion.

[edit] 3.2 S-IVB stage

Separation from the S-IVB stage and the S-IVB evasive maneuver were completed normally. The S-IVB stage was targeted for lunar impact by two firings of the auxiliary propulsion system. Lunar impact occurred approximately 87 hours into the mission at 4 degrees 12 minutes south latitude and 12 degrees 18 minutes west longitude, about 84 miles from the planned target point. The impact was recorded by the passive seismometers at the four lunar surface experiment stations. Figure 3-1 shows the location of the S-IVB impact on the lunar surface.

[edit] 3.3 Lunar orbit

[edit] 3.3.1 Orbital phase

The lunar orbit insertion maneuver placed the spacecraft into an orbit having a 170-mile apocynthion and a 52.6-mile pericynthion. About four hours later, the spacecraft orbit was lowered to one having a 59-mile apocynthion and a 14.5-mile pericynthion. After spending 17 hours in this lower orbit, the command and service module separated from the lunar module after which the command and service module orbit was circularized into one having a 70-mile apocynthion and a 54-mile pericynthion.

[edit] 3.3.2 Descent

Five minutes after the circularization maneuver was initiated by the command and service module, the lunar module performed the second descent orbit insertion maneuver. This lowered its pericynthion to within 6.2 miles of the lunar surface. An hour later, the lunar module powered descent was initiated and the lunar module landed on the moon at 110 hours 21 minutes 58 seconds. A manual target update of 3400 feet was incorporated early in the powered descent. Later in the descent maneuver, the Commander made eight landing point redesignations. These redesignations resulted in the spacecraft landing at 20 degrees 9 minutes 55 seconds north latitude and 30 degrees 45 minutes 57 seconds east longitude on the 1:25 000-scale Lunar Topographic Photomap of Taurus Littrow, First Edition, September, 1972.

[edit] 3.3.3 Ascent and rendezvous

The planned decay of the command and service module altitude to match the lunar module trajectory at rendezvous was not realized. This was similar to the experience of the Apollo 15 mission. Because of this, an orbital trim maneuver was performed to change the command and service module apocynthion to 67.3 miles and the pericynthion to 62.5 miles. An hour later, a plane change maneuver was performed to provide the proper orbital plane for rendezvous with the lunar module.

The lunar module ascended from the lunar surface at 185 hours 21 minutes 37 seconds after having been on the lunar surface for almost 75 hours. Approximately 7 1/2 minutes later, the ascent stage was inserted into lunar orbit. The achieved orbit required a vernier adjustment maneuver of 10 ft/sec to return the orbit to the planned conditions for rendezvous. The rendezvous was then completed normally, and the two vehicles were docked at 187 hours 37 minutes 15 seconds.

[edit] 3.3.4 Lunar module deorbit maneuver

The lunar module was jettisoned four hours after docking. The lunar module deorbit maneuver began about an hour and a half after jettisoning and impact occurred at 19 degrees 57 minutes 58 seconds north latitude, and 30 degrees 29 minutes 23 seconds east longitude, about 9.9 kilometers from the Apollo 17 landing site, and about 1.75 kilometers from the planned impact point (figs. 3-1 and 4-1).

[edit] 3.4 Transearth and entry trajectory

The command and service module remained in lunar orbit approximately 43 hours after the lunar module was jettisoned. The transearth injection maneuver was initiated at 234 hours 2 minutes 9 seconds. The maneuver was so accurate that only one midcourse correction was required during transearth coast, and that was at three hours prior to entry with a differential velocity of 2.1 ft/sec.

The command and service modules were separated 15 minutes before entry into the earth's atmosphere. The command module entered the atmosphere 1200 miles from the landing point and the landing occurred 1.3 miles short of the targeted point. The earth landing coordinates, as determined from the spacecraft computer, were 17 degrees 52 minutes 48 seconds south latitude and 166 degrees 6 minutes 36 seconds west longitude.

[edit] 4.0 Lunar Surface Science

The Apollo lunar surface experiments package for this mission consisted of the heat flow experiment, the lunar seismic profiling experiment, the lunar atmospheric composition experiment, the lunar ejecta and meteorites experiment, and the lunar surface gravimeter experiment. Other lunar surface experiments included the traverse gravimeter experiment, the surface electrical properties experiment, the lunar neutron probe experiment, the cosmic ray detector experiment, the lunar geological investigation, and the soil mechanics experiment.

Descriptions of the experiment equipment or references to documents in which the descriptions may be found are contained in Appendix A. A comprehensive discussion of the preliminary scientific results of the mission are contained in reference 1.

[edit] Summary of lunar surface activities

The landing point was in a cratered valley between two massifs. Figure 4-1 is a panoramic camera photograph of the Taurus-Littrow landing site. The variety of topographic features at the Taurus-Littrow landing site provided a valuable asset in the exploration of the lunar surface. The crew completed three periods of extravehicular activity during the 75 hours on the surface. The events of each of the three periods are summarized in table 4-I and the routes traversed are shown in figure 4-2. The arrangement of the experiment equipment is shown in figure 4-3. More detailed descriptions of the lunar surface activities are provided in sections 4.12 and 10.8.

Apollo Lunar Surface Experiments Package central station. Composite of AS17-136-20702 and AS17-136-20705, EVA 1 STA ALSEP pan frames.

[edit] 4.2 Apollo Lunar Surface Experiments Package central station

Figure 4-3. Apollo lunar surface experiments package and neutron probe deployment.

The site selected for deployment of the Apollo lunar surface experiments package was located approximately 185 meters west northwest (bearing of 287°) of the lunar module (fig. 4-3). During preparations for the traverse, the Lunar Module Pilot had difficulty removing the dome from the fuel cask where the fuel capsule is stowed. Insertion of the dome-removal tool and dome rotation to the unlocked position went smoothly; however, the tool extraction pull resulted in a separation of the tool from the dome. Using the chisel end of the geological hammer, the dome was pried from the cask. (Section 15.4.4 contains a discussion of this anomaly.) Removal of the fuel capsule from the cask and installation in the generator was completed normally. During the traverse to the deployment site, one of the two central station levelling blocks was knocked off; however, this did not adversely affect the deployment.

During the antenna alignment, centering of the east/west bubble level was difficult, and near the end of the third extravehicular activity, the antenna level settings were rechecked. The east/west bubble was against the east edge and the north/south bubble was centered, and no changes were made. This amount of misalignment causes a somewhat greater variation in signal strength during the lunar libation cycle, but it will not impact system commands or the transmission and reception of telemetry data.

Initial data were received at 0254 G.m.t. on December 12 and the received signal strength, radioisotope thermoelectric generator power, reserve power, and temperature status were all near the pre-mission predictions. The power output stabilized at 75.8 watts during the first lunar day and increased to 77.2 watts during the first lunar night. The automatic power management circuit is maintaining the average thermal plate temperature of the central station between 270.1° K and 324.8° K.

The telemetry signal power level, as received at various Spaceflight Tracking and Data Network sites, varied ±1.5 dBm in a sinusoidal manner around the normal level and this had no affect on the data. This variation was probably caused by a multipath phenomena produced by an antenna side-lobe reflection from the South Massif.

[edit] 4.3 Heat flow experiment

Figure 4-4. Relative locations of heat flow probes.

Two heat flow experiment (S-037) bore stems were drilled into the lunar surface to the planned depth of 254 centimeters and the probes were inserted during the first extravehicular activity (fig. 4-4).

The total power-on time required to drill bore stem 1 into the soil was 3 minutes 46 seconds. The penetration rate was variable with a particularly low penetration rate (40 centimeters per minute) occurring at a depth of about 80 to 100 centimeters. Between 120 and 200 centimeters depth, the penetration rate was 84 centimeters per minute, and in the final 50 centimeters, the rate slowed to about 6e centimeters per minute. Based on crew comments and televised visible sudden torques on the drill handles, some rock fragments were probably encountered during the drilling operations. The first meter of probe hole 2 was drilled more rapidly than that of probe 1 and below 200 centimeters, a resistant layer was encountered which slowed progress to about 60 centimeters per minute. Rock fragments were frequently encountered during the drilling of probe hole 2 which required a total power-on time of approximately 3 minutes.

The heat flow experiment was turned on at 0302 G.m.t. on December 12 and valid temperature data were received from all sensors. The operation of the experiment has been satisfactory. Probe 2 was operating before being inserted into the bore stem and a bore stem-and-probe temperature of about 300° K was indicated immediately after insertion. From December 12 to January 3, the experiment was operated in the normal gradient mode, which samples each sensor every 7.2 minutes. Between January 3 and January 24, eight low-conductivity experiments were conducted with a heater power of 0.002 watt. One high-conductivity experiment was performed on January 26.

The reference thermometer attached to the experiment electronics package radiator plate indicates that the package reaches a maximum temperature of 328° K at lunar noon, and remains at 290° K throughout the lunar night.

[edit] 4.4 Lunar seismic profiling experiment

The lunar seismic profiling experiment (S-203) geophone array was deployed at the lunar surface experiments site (fig. 4-3). The experiment was commanded on to verify instrument operation at 0358 G.m.t. on December 12.

The explosive packages were deployed as shown in figure 4-2 during the three extravehicular activity periods. All of the explosive charges were detonated by command and each of the geophones responded to the detonations. The detonation of explosive package 7 was observed through the television camera.

The central station was commanded to the high-bit-rate mode at 2229 G.m.t. on December 14 to record the impulse produced by the lunar module ascent. A strong seismic signal response from the geophone array was recorded.

The lunar seismic profiling experiment was again commanded to the high-bit-rate mode at 0636 G.m.t. on December 15 to record the lunar module ascent stage impact. The impact occurred at 19 degrees 59 minutes 24 seconds north and 30 degrees 30 minutes 36 seconds east at 0650 G.m.t. on December 15. The impact point was on the south slope of South Massif, about 8.4 kilometers southwest of the Apollo 17 landing site.

The recording of the seismic signals produced by the detonation of the eight explosive packages, together with the signal from the lunar module ascent stage impact, have enhanced the knowledge of the lunar structure. At the Taurus-Littrow site, the lunar near-surface material has an average seismic velocity of 250 meters per second to a depth of 248 meters. There is an indication of increased apparent velocities within the lunar near-surface material, suggesting the presence of possible inter-stratified material, perhaps thin lava flow. Beneath the 250 meters per second material, the seismic velocity increases to 1200 meters per second, characteristic of a competent lava flow. The thickness of the 1200 meters per second material is about 925 meters. Underlying the 1200 meters per second layer is material of an undetermined thickness which possesses a seismic velocity of about 4000 meters per second.

When the Apollo 17 data are combined with data from the earlier missions, it should be possible to determine the structure of the lunar crust to a depth of approximately 10 kilometers.

[edit] 4.5 Lunar atmospheric composition experiment

The lunar atmospheric composition experiment (S-205) deployment is shown in figure 4-3. All activities associated with the deployment were completed as planned. The dust cover was opened on December 18 at approximately 0420 G.m.t. after the last lunar seismic profiling experiment explosive package was detonated. After allowing the radiator temperature to decrease from a peak of 340.8° K (before cover removal), to 327.5° K, nine hours of ion source outgassing was accomplished the following day with a temperature of 523° K having been reached.

The first activation of the experiment occurred on December 27 at approximately 1800 G.m.t. The instrument responded well to commands and was operating normally except for a background count ramp in the low- and mid-mass channels. The presence of this interference will not cause the loss of data, but it will increase the difficulty in reducing the data from this portion of the spectrum. This anomaly is discussed in section 15.4.5.

Operation throughout the first lunation was characterized by good performance of the instrument except for two occasions during lunar sunrise when the instrument switched into the high-voltage-lock mode, which stopped the stepping of the sweep voltage. Two logic system noise bursts, which occurred just after sunrise, may have caused the sweep high voltage to be commanded into lock. On both occasions, the situation was properly rectified by commanding the sweep high voltage back on.

Many residual peaks were observed in the spectrum, but only the helium peak is clearly native to the moon. The remainder are at least partially due to outgassing of the instrument, the lunar module, and the Apollo lunar surface experiments package, as evidenced by the peaks decreasing in amplitude throughout the lunar night.

Sunrise brought a large increase in all peaks in the spectrum except helium which decreased as would be expected if it were a native noncondensible gas. Operation was curtailed 24 hours after sunrise because of the very high gas densities in the ion source chamber (approximately 109 molecules per cubic centimeter) from material outgassing. A 15-minute period of operation was performed at lunar noon. Full-time operation was begun again a few hours before sunset on January 23. There was a marked decrease in gas densities about the time of sunset.

Daytime operation will be limited to those times when the outgassing levels are tolerable. As indicated by the data from previous missions, the instrument, site, and other artifacts will eventually be sufficiently free of outgassing contaminants to enable the lunar atmospheric composition experiment to produce high quality data.

[edit] 4.6 Lunar ejecta and meteorites experiment

The lunar ejecta and meteorites experiment (S-202) deployment is shown in figure 4-3. The radiator mirror was uncovered at 0957 G.m.t. on December 21, after detonation of the last explosive package and when the internal structural temperature had decreased to 344° K. The experiment was operated for about 15 hours on December 22 but was turned off because of rising temperatures. The experiment was turned on again on December 23 to record the background noise rate for the instrument. The sensor covers were not removed until December 28, after completion of continuous operation which encompassed about 60 hours of lunar day and about 50 hours of lunar night. The instrument data indicate that the background noise rate was essentially zero.

The instrument is in the full operating mode from sun angles of 20° before sunset through 20° after sunrise because of a thermal control problem during the lunar day. Section 15.4.3 contains a discussion of this anomaly. Fortunately, the instrument measurements of ejecta are best performed during the lunar night when the primary particle impact rates are near zero. The instrument will remain off during most of the lunar day until the science objectives which can be achieved during lunar night are fulfilled or until satisfactory thermal control can be attained.

The measurements indicate that the detected number of lunar ejecta particles compare within an order of magnitude to the number of primary particles. The measurements are verifying that the bulk of cosmic dust material comes from the general direction of the sun which agrees with the results obtained from similar instruments carried on Pioneer 8 and 9.

[edit] 4.7 Lunar surface gravimeter experiment

The lunar surface gravimeter experiment (5-207) (fig. 4-3) was activated at 0523 G.m.t. on December 12, and following activation, the data (science and engineering) indicated normal operations. However, the addition of all masses apparently set the sensor beam against the lower stop and removal of one mass apparently moved the beam against the upper stop. Operation of the adjustment screws failed to null the beam and the second adding of all masses failed to move the beam to the lower stop. This anomaly is discussed in section 15.4.1.

On January 3, 1973, the experiment was re-configured, and the sensor beam was centered by adjusting the mass change mechanism to obtain longterm seismic and free-mode science data. In this revised configuration, tidal data are not being obtained, but the experiment is collecting longterm seismic and free mode information.

The lunar surface gravimeter experiment sensor's initial on-scale temperature of 321.5° K occurred at about 2054 G.m.t., December 14, some 63 hours after initial turn-on. The experiments sensor temperature now remains stabilized at 322.323° K. The instruments subsystem components continue to operate normally providing engineering status data.

[edit] 4.8 Traverse gravimeter experiment

The traverse gravimeter experiment (S-199) made an earth-moon gravity tie and obtained the value of gravity at various stops along the traverses, relative to the value of gravity at the landing site. Using absolute gravity measurements on the Earth, a preliminary value of 162 694 (±5) milligals was obtained at the Taurus-Littrow landing site. The number of stations (12) at which discrete gravity measurements were made (fig. 4-2 and table 4-I) was about as planned with an extra measurement being made at station 2A and no measurements taken at station because of time constraints.

The hardware performed satisfactorily except for differences between measurements made on the lunar roving vehicle and measurements made with the experiment resting on the surface at the same sites. The values measured on the surface were always lower. The difference in the gravity measurement at the landing point was 4.6 milligals, at station 8 it was 6.9 milligals, and at station 9 it was 6.2 milligals. The reason for this discrepancy is not known. In initial postflight calculations, an empirical correction of -6 milligal was established for all values measured when the experiment was mounted on the lunar roving vehicle.

A preliminary analysis of the data has been made by projecting it to a northwest-southeast profile and by making two dimensional approximations for all the reductions and interpretations. Free-air and Bouguer corrections were applied to the data. The resultant Bouguer corrections shows values at stations 2A and 8, near the South and North Massifs, respectively, which are more than 20 milligals lower than the value at the landing site. The variation of Bouguer values in the central part of the valley are relatively small, although the value at station 4 is a few milligals higher and the value at station 5 is a few milligals lower than the value at the landing site. A preliminary interpretation of the gross features of the gravity profile is a model with basalt flows having a positive density contrast of 0.8 gram per cubic centimeter and a thickness of 1 kilometer buried under the valley floor.

[edit] 4.9 Surface electrical properties experiment

The surface electrical properties experiment (S-204) was deployed as shown in figure 4-2, and was utilized during portions of both the second and third extravehicular activity periods. During the transmitter deployment, a problem was encountered in keeping the solar panel open because of memory in the solar panel wiring harness. The crew resolved the problem by taping the panel fully open. Also, during the deployment of the transmitter antennas, the two sets of dipoles were reversed from the planned orientation. The effect of the reversal was corrected in the data reduction process with no loss of data.

A thermal control problem with the surface electrical properties receiver caused the premature termination of the experiment. This problem is discussed in detail in section 15.4.2.

Despite these problems, when the surface electrical properties experiment recorder was returned to earth, 1 hour and 42 minutes of data had been obtained.

[edit] 4.10 Lunar neutron probe experiment

The lunar neutron probe experiment (S-229) was deployed as shown in figure 4-3 and emplaced in the deep drill core hole during the first extravehicular activity period. The 2-meter probe was retrieved and deactivated at the end of the third extravehicular activity period, accruing 49 hours of exposure. The site was approximately 38 meters north of the Apollo lunar surface experiments package radioisotope thermoelectric generator (fig. 4-3). Corrections required because of the proximity of the generator, which is a strong source of neutrons, should be small; although experimentation is necessary to determine the size of the correction.

The probe was returned, disassembled, and the targets and detectors were in excellent condition.

The background due to the direct interaction of the fast neutrons from the radioisotope thermoelectric generator with the plastic was measured, and appears to be negligible.

Only the mica detectors have been completely examined. Analysis of the remaining detectors and data is continuing and will be completed after postflight calibration of the probe. Although the calibration data have not been completely processed, the track densities are in the expected range. The neutron capture rates appear to be within a factor of two of those estimated from the theoretical calculations.

[edit] 4.11 Cosmic ray detector experiment

The cosmic ray detector experiment (S-152) was deployed by pulling the slide cover open and hanging the cover in the shade while the box was in the sun on the lunar module. In both cases, the nuclear particle detectors faced outward from the lunar module. The detectors were exposed to the lunar environment for approximately 45.5 hours. No degradation of any of the detector surfaces was found. Microscopic examination of the detector surfaces showed very little dust. The maximum temperature of approximately 4000 K (as shown by temperature labels) was well below the critical limit.

The tracks of heavy solar wind ions are clearly visible, as are the tracks of intermediate-energy heavy particles. The flux of the latter is surprisingly high (approximately 6 x 103 tracks per square centimeter) and indicate that the sun emits an appreciable flux of particles in the range of 10 keV per nucleon to 10 meV per nucleon, even at times of quiet sun. These particles were found in both the shade and sun detectors and thus are not directly associated with the solar wind. The tracks have been seen in the mica, glass, and plastic detectors. The energy spectrum is similar to that of solar flares. This intermediate energy component is possibly associated with a visually active sun spot area that was present during the entire Apollo 17 mission. This experiment is the first flown that could have detected the presence of the intermediate-energy particles. The presence of the intermediate-energy particles will limit the degree to which the radon atmosphere can be established at the Apollo 17 site, but this constitutes no degradation of the basic experiment.

Edits and errors by Eric Hartwell are licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 2.5 license. The original NASA material is copyright-free.