The Tenth Mission:

The Fifth Lunar Landing

16 April–27 April 1972





Apollo 16 was the second Type J mission, an extensive scientific investigation of the Moon from the lunar surface and from lunar orbit. The vehicles and payload were similar to those of Apollo 15.


The primary objectives were:





The crew members were Captain John Watts Young (USN), commander; Lt. Commander Thomas Kenneth “Ken” Mattingly, II (USN), command module pilot; and Lt. Colonel Charles Moss Duke, Jr. (USAF), lunar module pilot.


Selected as an astronaut in 1962, Young was making his fourth spaceflight, only the second astronaut to achieve that distinction. He had been pilot of Gemini 3 command pilot of Gemini 10, and command module pilot of Apollo 10, the first test of the LM in lunar orbit and the dress rehearsal for the first piloted landing on the Moon. Born 24 September 1930 in San Francisco, California, Young was 41 years old at the time of the Apollo 16 mission. He received a B.S. in aeronautical engineering from the Georgia Institute of Technology in 1952. His backup for the mission was Fred Wallace Haise, Jr.


Mattingly, who had been removed from the Apollo 13 mission because of his susceptibility to German measles, was making his first spaceflight. Born 17 March 1936 in Chicago, Illinois, Mattingly was 36 years old at the time of the Apollo 16 mission. He received a B.S. in aeronautical engineering from Auburn University in 1958, and was selected as an astronaut in 1966. His backup was Lt. Colonel Stuart Allen Roosa (USAF).


Duke was making his first spaceflight. Born 3 October 1935 in Charlotte, North Carolina, he was 36 years old at the time of the Apollo 16 mission. Duke received a B.S. in Naval sciences from the U.S. Naval Academy in 1957 and an M.S. in aeronautics and astronautics from the Massachusetts Institute of Technology in 1964. He was selected as an astronaut in 1966 and his backup was Captain Edgar Dean Mitchell (USN).


The capsule communicators (CAPCOMs) for the mission were Major Donald Herod Peterson (USAF), Major Charles Gordon Fullerton (USAF), Colonel James Benson Irwin (USAF), Haise, Roosa, Mitchell, Major Henry Warren Hartsfield, Jr. (USAF), Anthony Wayne “Tony” England, Ph.D., and Lt. Colonel Robert Franklyn Overmyer (USMC). The support crew consisted of Peterson, England, Hartsfield, and Phillip Kenyon Chapman, Sc. D. The flight directors were M. P. “Pete” Frank and Philip C. Shaffer (first shift), Eugene F. Kranz and Donald R. Puddy (second shift), and Gerald D. Griffin, Neil B. Hutchinson, and Charles R. Lewis (third shift).


The Apollo 16 launch vehicle was a Saturn V, designated SA-511. The mission also carried the designation Eastern Test Range #1601. The CSM was designated CSM-113, and had the call-sign “Casper.” The lunar module was designated LM-11, and had the call-sign “Orion.”



Launch Preparations


The terminal countdown was picked up at T-28 hours at 03:54:00 GMT on 15 April. Scheduled holds were initiated at T-9 hours for 9 hours and at T-3 hours 30 minutes for one hour.


At launch time, the Cape Kennedy launch area was experiencing fair weather resulting from a ridge of high pressure extending westward, from the Atlantic Ocean through central Florida. Cumulus clouds covered 20 percent of the sky (base 3,000 feet), the temperature was 88.2° F, the relative humidity was 44 percent, and the barometric pressure was 14.769 lb/in2. The winds, as measured by the anemometer on the light pole 60.0 feet above ground at the launch site measured 12.2 knots at 269° from true north. The winds at 530 feet above the launch site measured 9.9 knots at 256° from true north.



Ascent Phase


Apollo 16 launched from Kennedy Space Center Launch Complex 39, Pad A, at a Range Zero time of 17:54:00 GMT (12:54:00 p.m. EST) on 16 April 1972. The planned launch window extended to 21:43:00 GMT to take advantage of a sun elevation angle on the lunar surface of 11.9°.


Between 000:00:12.7 and 000:00:31.8, the vehicle rolled from a launch pad azimuth of 90° to a flight azimuth of 72.034°. The S-IC engine shut down at 000:02:41.78, followed by S-IC/S-II separation, and S-II engine ignition. The S-II engine shut down at 000:09:19.54 followed by separation from the S-IVB, which ignited at 000:09:23.60. The first S-IVB engine cutoff occurred at 000:11:46.21 with deviations from the planned trajectory of only +0.6 ft/sec in velocity; altitude was exactly as planned.


The maximum wind conditions encountered during ascent were 50.7 knots at 257° from true north at 38,880 feet, with a maximum wind shear of 0.0095 sec-1 at 44,780 feet.


Parking orbit conditions at insertion, 000:11:56.21 (S-IVB cutoff plus 10 seconds to account for engine tailoff and other transient effects), showed an apogee and perigee of 91.3 by 90.0 n mi, an inclination of 32.542°, a period of 87.85 minutes, and a velocity of 25,605.1 ft/sec. The apogee and perigee were based upon a spherical Earth with a radius of 3,443.934 n mi.


The international designation for the CSM upon achieving orbit was 1972-031A and the S-IVB was designated 1972-031B. After undocking at the Moon, the LM ascent stage would be designated 1972-031C, the descent stage 1972-031E, and the particles and fields subsatellite 1972-031D.



Translunar Phase


After inflight systems checks, the 341.92-second translunar injection maneuver (second S-IVB firing) was performed at 002:33:36.50. The S-IVB engine shut down at 002:39:18.42 and translunar injection occurred ten seconds later, at a velocity of 35,566.1 ft/sec after 1.5 Earth orbits lasting 2 hours 37 minutes 32.21 seconds.


At 003:04:59.0, the CSM was separated from the S-IVB stage, transposed, and docked at 003:21:53.4. The docked spacecraft were ejected from the S-IVB at 003:59:15.1, and an 80.2-second separation maneuver was performed at 004:18:08.3. Color television was transmitted for 18 minutes during the transposition and docking.


At 005:40:07.2, a 54.2-second propulsive force from the S-IVB auxiliary propulsion system targeted the S-IVB for impact on the Moon near the Apollo 12 landing site. As on previous missions, S-IVB impact was desired to produce seismic vibrations that could be used to study the nature of the lunar interior structure. Although launch vehicle systems malfunctions precluded a planned trajectory refinement, the impact point was within the desired area. A transponder failure at 027:09:59 caused loss of S-IVB telemetry and prevented determination of a precise impact time, making interpretation of seismic data uncertain. However, it is estimated that the S-IVB impacted the lunar surface at 075:08:04. The estimated impact point was latitude 1.3° north and longitude 23.8° west, 173 n mi from the target point, 71 n mi from the Apollo 12 seismometer, 131 n mi from the Apollo 14 seismometer, and 593 n mi from the Apollo 15 seismometer. At impact, the S-IVB weighed 30,805 pounds and was traveling 8,202 ft/sec.


During the CSM/LM docking, light colored particles were noticed coming from the LM area. The particles were unexplained. At 007:18, the crew reported a stream of particles emitting from the LM in the vicinity of aluminum close-out panel 51, which covered the Mylar insulation over reaction control system A. This panel was located below the docking target on the +Z face of the LM ascent stage.


To determine systems status, the crew entered the LM at 008:17 and powered up. All systems were normal and the LM was powered down at 008:52. The CM television was turned on at 008:45 to give the mission control center a view of the particle emission. In order to point the high gain antenna, panel 51 was rotated out of sunlight and a marked decrease was then noted in the quantity of particles. On the television picture, the source of the particles appeared to be a growth of grass-like particles at the base of the panel. The television was turned off at 009:06. Results of the investigation determined that the particles were shredded thermal paint, and that the degraded thermal protection due to the paint shredding would have no effect on subsequent LM operations.


The 45-minute inflight electrophoresis demonstration commenced on schedule at 025:05 and was successful. Ultraviolet photography of the Earth from 58,000 and 117,000 n mi was accomplished as planned.


The only required midcourse correction was made at 030:39:00.66. It lasted 2.01 seconds and was required to ensure proper lunar orbit insertion.


At 038:18:56, the command module computer received an indication that an inertial measurement unit gimbal lock had occurred. The computer correctly downmoded the IMU to “coarse align” mode and set the appropriate alarms. Due to the large number of LM panel particles floating near the spacecraft and blocking the command module pilot’s vision of the stars, realignment of the platform was accomplished using the Sun and Moon. It was suspected that the gimbal lock indication was an electrical transient caused by actuation of the thrust vector control enable relay when exiting the IMU alignment program. A program was uplinked to the crew and entered into the computer. The program would allow the computer to ignore gimbal lock indication during critical periods.


The visual light flash phenomena experiment started at 049:10. Numerous flashes were reported by the crew prior to terminating the experiment at 050:16. The crew also reported the flashes left no after-glow, were instantaneous, and were white.


The second LM housekeeping commenced about 053:30 and was completed at 055:11. All LM system checks were normal. The SM scientific instrumentation module door was jettisoned at 069:59:01.


At 074:28:27.87, at an altitude of 92.9 n mi above the Moon, the service propulsion engine was fired for 374.90 seconds to insert the spacecraft into a lunar orbit of 170.3 by 58.1 n mi. The translunar coast had lasted 71 hours 55 minutes 14.35 seconds.



Lunar Orbit/Lunar Surface Phase


At 078:33:45.04, a 24.35-second service propulsion system maneuver was performed to reach the descent orbit of 58.5 by 10.9 n mi for undocking of the LM.


LM activation started at 093:34, about 11 minutes early. The LM was powered up and all systems were nominal.


Lunar module undocking and separation were performed at 096:13:31. The CSM was scheduled to perform an orbit circularization maneuver on the 13th lunar revolution at 097:41:44, but oscillations were detected in a secondary system that controlled the direction of thrust of the service propulsion system engine.


While flight controllers evaluated the problem, the CSM maneuvered into a stationkeeping situation with the LM and prepared either to redock or continue the mission. After 5 hours 45 minutes, tests and analyses showed that the system was still usable and safe; therefore, the vehicles were separated again and the mission continued on a revised time line. A separation maneuver was performed at 102:30:00 and the platforms were realigned at 102:40.


At 103:21:43.08, the service propulsion system was fired for 4.66 seconds to place the CSM in a lunar orbit of 68.0 by 53.1 n mi in preparation for the acquisition of scientific data.


The 734-second powered descent engine firing began at 104:17:25 at an altitude of 10.994 n mi. Landing occurred at 02:23:35 GMT on 21 April (09:23:35 p.m. EST on 20 April) at 104:29:35.


The spacecraft landed in the Plain of Descartes at latitude 8.97301° south and longitude 15.50019° east, 668 feet north and 197 feet west of the planned landing site. Approximately 102 seconds of engine firing time remained at landing.


Image from Apollo 16 pan camera frame 4623 shows area around LM landing site. Palmetto Crater is at the top. The detail image in the next column clearly shows the LM as a black spot, with white streaking from the descent engine plume. The crater in the center is Spook and to the upper left is Flag Crater.


Because the LM had remained in lunar orbit six hours longer than planned, the LM was powered down to conserve electrical power and the first extravehicular activity was delayed in order to provide the crew with a well-deserved sleep period.


The LM cabin was depressurized at 118:53:38 for the first extravehicular activity period. Television coverage of surface activity was delayed until the LRV systems were activated because the LM steerable antenna, used for initial lunar surface television transmission, remained locked in one axis and could not be used.


The lunar surface experiments package was successfully deployed, but the commander accidentally tripped over the electronics cable, breaking it, and rendering the heat flow experiment inoperative.


This photo, taken during EVA-1, shows the undulating terrain of the landing site, with the LM in the center in the distance. In the foreground is the PSE, with the mortar pack at the left (NASA AS16-113-18359).


After completing their activities at the experiments site, the crew drove the lunar roving vehicle (LRV-2) west to Flag Crater where they made visual observations, photographed items of interest, and collected lunar samples.


The inbound traverse route was just slightly south of the outbound route, and the next stop was Spook Crater. The crew then returned by way of the experiment station to the LM, at which time they deployed the solar wind composition experiment.


Several LRV problems occurred during EVA-1. While ascending ridges and traversing very rocky terrain, there was no response from the rear wheels when full throttle was applied. The vehicle continued to move, but the front wheels were digging into the surface.


The crew entered the LM and the cabin was repressurized at 126:04:40.


The first extravehicular activity lasted 7 hours 11 minutes 2 seconds. The distance traveled in the lunar rover vehicle was 2.3 n mi (4.2 km), vehicle drive time was 43 minutes, the vehicle was parked for 3 hours 39 minutes, and 65.92 pounds (29.9 kg) of samples were collected.


After 16 hours, 30 minutes in the LM, the crew depressurized the cabin at 142:39:35 to begin the second extravehicular period.


After preparing the LRV, the crew headed south-southeast to a mare sampling area near the Cinco Craters on the north slope of Stone Mountain. They then drove in a northwesterly direction, making stops near Stubby and Wreck Craters. The last leg of the traverse was north to the experiments station and the LM.


Later, at station 8, a rear-drive troubleshooting procedure was implemented. During this procedure, a mismatch of power mode switching was identified as the cause of the problem. After a change in switch configuration, the LRV was working properly. An hour and a half later, at stations 9 and 10, the LRV range, bearing, and distance were reported to be inoperative. However, navigation heading was working. When the crew reset the power switches, the navigation system began operating nominally.


After the crew arrived at station 10 (LM and ALSEP area), the surface activity was extended about 20 minutes because the crew’s consumables usage was lower than predicted. The lunar module pilot then examined the damaged heat flow experiment. Visual inspection revealed that the cable separated at the connector. Results of troubleshooting a model of the experiment at mission control indicated a fix could be accomplished. However it was not attempted because the time required could affect the third EVA.


The period ended with ingress and repressurization of the LM cabin at 150:02:44. During ingress, a two-inch portion of the commander’s antenna was broken off, which produced a 15 to 18 db drop in signal strength. Because the commander’s backpack radio relayed the lunar module pilot’s information to the LM and the lunar communications relay unit for transmission to ground stations, a decision was made later to have the commander use the lunar module pilot’s oxygen purge system, which supported the antenna.


The second extravehicular activity lasted 7 hours 23 minutes 9 seconds. The distance traveled in the lunar rover vehicle was 6.1 n mi (11.3 km), vehicle drive time was 1 hour 31 minutes, park time was 3 hours 56 minutes, and 63.93 pounds (29.0 kg) of samples were collected.


The third extravehicular period began 30 minutes early when the cabin was depressurized at 165:31:28, but four stations were deleted because of time limitations.


The crew first drove to the rim of North Ray Crater where photographs were taken and samples gathered, some from House Rock, the largest single rock seen during the extravehicular activities. The extra 30 minutes were used at North Ray Crater.


They then drove southeast to the second sampling area, Shadow Rock. On completing activities there, the crew drove the vehicle back to the LM, retracing the outbound route.


The crew reentered the LM and the cabin was repressurized at 171:11:31, thus ending the fifth human exploration of the Moon.


The third extravehicular activity lasted 5 hours 40 minutes 3 seconds. The distance traveled in the lunar rover vehicle was 6.2 n mi (11.4 km), vehicle drive time was 1 hour 12 minutes, the vehicle was parked for 2 hours 26 minutes, and 78.04 pounds (35.4 kg) of samples were collected.


For the mission, the total time spent outside the LM was 20 hours 14 minutes 14 seconds, the total distance traveled in the lunar rover vehicle was 14.5 n mi (26.9 km), vehicle drive time was 3 hours 26 minutes, the vehicle was parked during extravehicular activities for 10 hours 1 minute, and the collected samples totaled 211.00 pounds (95.71 kg; official total in kilograms as determined by the Lunar Receiving Laboratory in Houston). The farthest point traveled from the LM was 15,092 feet.


While the crew was on the surface, the command module pilot had obtained photographs, measured physical proper ties of the Moon, and made visual observations. He also made comprehensive deep space measurements, providing scientific data that could be used to validate findings from the Apollo 15 mission. A 7.14-second CSM plane change maneuver was made at 169:05:52.14 and adjusted the orbit to 64.6 by 55.0 n mi.


Ignition of the ascent stage engine for lunar liftoff occurred at 01:25:47 GMT on 24 April (at 08:25:47 p.m. EST on 23 April) at 175:31:47.9 and was televised. The LM had been on the lunar surface for 71 hours 2 minutes 13 seconds.


The 427.8-second firing of the ascent engine placed the vehicle into a 40.2 by 7.9 n mi orbit. Several rendezvous sequence maneuvers were required before docking could occur two hours later. First, a vernier adjustment was made at 175:42:18 at an altitude of 11.2 n mi. Then the terminal phase was initiated with a 2.5 second maneuver at 176:26:05. This maneuver brought the ascent stage to an orbit of 64.2 by 40.1 n mi. Following a nominal rendezvous sequence, the ascent stage docked with the CM at 177:41:18 at an altitude of 65.6 n mi, after being undocked for 81 hours 27 minutes 47 seconds.


LM ascent stage, seen against the Sea of Fertility, approaches the CSM following a successful lunar surface expedition (AS16-122-19533).


After the crew transferred the samples, film, and equipment to the CSM, the ascent stage was jettisoned at 195:00:12 at an altitude of 59.2 n mi. After jettison, the LM lost stability and began tumbling at a rate of about 3° per second. This may have been due to a guidance circuit breaker inadvertently being left open. A maneuver was made at 195:03:13 to separate the CSM from the ascent stage. No deorbit burn maneuver was possible, and the ascent stage remained in lunar orbit for approximately one year.[1]


The SM mass spectrometer deployment boom stalled during a retract cycle and was, therefore, jettisoned at 195:23:12.


Before the CSM was maneuvered from lunar orbit, a particles and fields subsatellite similar to that deployed from Apollo 15 was deployed at 196:02:09 during the 62nd revolution into an orbit of 66 by 52 n. mi. at an inclination of -110°. The subsatellite was instrumented to measure plasma and energetic-particle fluxes, vector magnetic fields, and subsatellite velocity from which lunar gravitational anomalies could be determined. It was scheduled to be released during the 73rd revolution into an orbit of 170 by 58 n. mi. However, as a result of the engine gimbal anomaly earlier in the mission, a planned CSM orbit-shaping maneuver was not performed before ejection of the subsatellite and the it was placed into an orbit with a much shorter lifetime than planned.


Because of communications interference resulting from the failure of the ascent stage to deorbit, it was not possible to activate the subsatellite until 20 hours after launch. Loss of all tracking and telemetry data occurred at 20:31 GMT on May 29, 1972. Reacquisition of the signal was expected at 22:00 GMT on that day, but was not achieved. It is believed that the subsatellite struck the far side of the lunar surface during the 425th revolution at longitude 110° east. The lower-than-desired orbit contributed to the short orbital life because the lunar mass concentrations (“mascons”) on the front and far sides of the Moon were located near the subsatellite’s ground track.


The second CSM plane-change maneuver and some orbital science photography were deleted so that transearth injection could be performed 24 hours earlier than originally planned. This decision was made due to the engine problem experienced during the lunar orbit circularization maneuver.


Following a 162.29-second maneuver at 200:21:33.07 at an altitude of 52.2 n mi, transearth injection was achieved at 200:24:15.36 at a velocity of 8,663.0 ft/sec after 64 lunar orbits lasting 125 hours 49 minutes 32.59 seconds.



Transearth Phase


Between 202:57 and 203:12, good quality television pictures were transmitted from inside the CM. From 203:29 to 204:12, pictures were broadcast from the LRV camera on the lunar surface.


The first of two midcourse corrections, a 22.6-second 3.4-ft/sec maneuver, was made at 214:35:02.8 to achieve the desired entry interface conditions with Earth.


At 218:39:46, the command module pilot began a transearth coast EVA. Television coverage was provided for the 1 hour 23 minute 42 second period, during which He retrieved film cassettes from the scientific instrument module cameras, visually inspected the equipment, and exposed an experiment for ten minutes to provide data on microbial response to the space environment. This brought the total extravehicular activity for the mission to 22 hours 17 minutes 36 seconds.


A scheduled television press conference started at 243:35 and lasted for 18 minutes. During the conference, the crew gave a brief description of the farside of the Moon. An item of particular interest was the crew’s description of Guyot Crater, which appeared to be full of material. The material seemed to have overflowed and spilled down the side of the crater. The crew compared their observations with similar geological formations in Hawaii.


Additional activities during transearth coast included photography for a Skylab program study of the behavior and effects of particles emanating from the spacecraft, and the second light-flash observation session. The second midcourse correction, a 6.4-second maneuver of 1.4 ft/sec, was made at 262:37:20.7.





The service module was jettisoned at 265:22:33, and the CM entry followed a normal profile. The command module reentered Earth’s atmosphere (400,000 feet altitude) at 265:37:31 at a velocity of 36,196.1 ft/sec, following a transearth coast of 65 hours 13 minutes 16 seconds.


While on the drogue parachutes, the CM was viewed on television, and continuous coverage was provided through crew recovery.


The parachute system effected splashdown of the CM in the Pacific Ocean at 19:45:05 GMT (02:45:05 p.m. EST) on 27 April. Mission duration was 265:51:05. The impact point was about 3.0 n mi from the target point and 2.7 n mi from the recovery ship U.S.S. Ticonderoga. The splashdown site was estimated to be latitude 0.70° south and longitude 156.22° west. After splashdown, the CM assumed an apex-down flotation attitude, but was successfully returned to the normal flotation position in 4 minutes 25 seconds by the inflatable bag uprighting system.


The crew was retrieved by helicopter and was aboard the recovery ship 37 minutes after splashdown. The CM was recovered 62 minutes later. The estimated CM weight at splashdown was 11,995 pounds, and the estimated distance traveled for the mission was 1,208,746 n mi.


The crew remained aboard the Ticonderoga until 17:30 GMT on 29 April, when they were flown to Hickam Air Force Base, Hawaii, where they arrived at 19:21 GMT. They departed by C-141 aircraft for Ellington Air Force Base, Houston, at 20:07 GMT and arrived at 03:40 GMT on 30 April.


The CM arrived in Hawaii at 03:30 GMT on 30 April. At 18:00 GMT on 1 May, it departed for North Island Naval Air Station, San Diego, for deactivation, where it arrived at 00:00 GMT on 6 May.


On May 7, while propellants were being removed from the CM, a tank cart exploded because of overpressurization. Forty-six persons suspected of inhaling toxic fumes were hospitalized, but examination revealed no symptoms of inhalation. The CM was not damaged. An investigation board reported that the ratio of neutralizer to oxidizer being detanked had been too low because of the extra oxidizer retained in the CM tanks as a result of the Apollo 15 parachute anomaly. Changes would be made in ground support equipment and detanking procedures to prevent future overpressurization. Deactivation was completed at 00:00 GMT on 11 May. The CM left North Island at 03:00 GMT on 12 May, and was transferred to the North American Rockwell Space Division facility at Downey, California, for postflight analysis. It arrived at 10:30 GMT on 12 May.





The overall performance of the Apollo 16 mission was excellent, with all of the primary mission objectives and most of the detailed objectives being met, although the mission was terminated one day earlier than planned. Experiment data were gathered during lunar orbit, from the lunar surface, and during both the translunar and transearth coast phases for all detailed objectives and experiments except subsatellite tracking for autonomous navigation and the heat flow experiment. Especially significant scientific findings included the first photography obtained of the geocorona in the hydrogen (Lyman alpha) wavelength from outside Earth’s atmosphere, and the discovery of two new auroral belts around Earth. The following conclusions were made from an analysis of post-mission data:


  1. Lunar dust and soil continued to cause problems with some equipment, although procedural measures were taken and equipment changes and additions were made to control the condition.


  1. Loss of the heat flow experiment emphasized that all hardware should be designed for loads accidentally induced by crew movements because of vision and mobility constraints while wearing the pressurized suits.


  1. The capability of the S-band omni-directional antenna system to support the overall lunar module mission operations was demonstrated after the failure experienced with the S-band steerable antenna.


  1. The performance of the Apollo 16 particles and fields subsatellite showed that the lunar gravitational model was not sufficiently accurate for the orbital conditions that existed to accurately predict the time of impact.


  1. The absence of cardiac arrhythmias on this mission was, in part, attributed to a better physiological balance of electrolytes and body fluids resulting from an augmented dietary intake of potassium and a better rest-work cycle that effectively improved the crew’s sleep.


  1. The ability of the crew and the capability of the spacecraft to land safely in the rough terrain of a lunar highlands region without having high resolution photography prior to the mission was demonstrated. Further, the capability of the lunar roving vehicle to operate under these conditions and on slopes up to 20° was demonstrated.


[1] Later analysis indicated that the ascent stage struck the lunar surface before Apollo 17 commenced, but no data were available for substantiation.