Editing Apollo 16 (section)

===Return to Earth===
[[File:S72-37001.jpg|thumb|Ken Mattingly performing his deep-space [[Extravehicular activity|EVA]], retrieving film cassettes from the CSM's exterior]]
Eight minutes before the planned departure from the lunar surface, CAPCOM [[James Irwin]] notified Young and Duke from Mission Control that they were go for liftoff. Two minutes before launch, they activated the "Master Arm" switch and then the "Abort Stage" button, causing small explosive charges to sever the ascent stage from the [[Apollo Lunar Module#Descent stage|descent stage]], with cables connecting the two severed by a [[guillotine]]-like mechanism. At the pre-programmed moment, there was liftoff and the ascent stage blasted away from the Moon, as the camera aboard the LRV followed the first moments of the flight. Six minutes after liftoff, at a speed of about {{convert|5000|km/h|mph|sp=us}}, Young and Duke reached lunar orbit.<ref name=honeysuckle/><ref>{{cite web|title=Return to Orbit|url=http://www.hq.nasa.gov/alsj/a16/a16.launch.html|publisher=[[NASA]]|editor-first=Eric M.|editor-last=Jones|editor2-first=Ken|editor2-last=Glover|work=Apollo 16 Lunar Surface Journal|access-date=November 29, 2011|archive-date=December 31, 2020|archive-url=https://web.archive.org/web/20201231213251/https://www.hq.nasa.gov/alsj/a16/a16.launch.html|url-status=live}}</ref> Young and Duke rendezvoused and re-docked with Mattingly in the CSM. To minimize the transfer of lunar dust from the LM cabin into the CSM, Young and Duke cleaned the cabin before opening the hatch separating the two spacecraft. After opening the hatch and reuniting with Mattingly, the crew transferred the samples Young and Duke had collected on the surface into the CSM for transfer to Earth. After transfers were completed, the crew would sleep before jettisoning the empty Lunar Module ascent stage the next day, when it was to be crashed intentionally into the lunar surface in order to calibrate the seismometer Young and Duke had left on the surface.<ref name="fullsummary" />

The next day, after final checks were completed, the expended LM ascent stage was jettisoned.<ref name=lmjett>{{cite web|title=Apollo 16: Day 9 Part 2 – LM Jettison and Trans Earth Injection|url=https://history.nasa.gov/ap16fj/25_Day9_Pt2.htm|work=Apollo 16 Flight Journal|archive-url=https://web.archive.org/web/20111021155938/http://history.nasa.gov/ap16fj/25_Day9_Pt2.htm|archive-date=October 21, 2011|url-status=dead|editor-first=David|editor-last=Woods|editor2-first=Tim|editor2-last=Brandt|publisher=[[NASA]]}}</ref> Likely because of a failure by the crew to activate a certain switch in the LM before sealing it off, it tumbled after separation. NASA could not control it, and it did not execute the rocket burn necessary for the craft's intentional de-orbit. The ascent stage eventually crashed into the lunar surface nearly a year after the mission. The crew's next task, after jettisoning the Lunar Module ascent stage, was to release a subsatellite into lunar orbit from the CSM's scientific instrument bay. The burn to alter the CSM's orbit to that desired for the subsatellite had been cancelled; as a result, the subsatellite lasted just over a month in orbit, far less than its anticipated one year. Just under five hours after the subsatellite release, on the CSM's 65th orbit around the Moon, its service propulsion system main engine was reignited to propel the craft on a trajectory that would return it to Earth. The SPS engine performed the burn flawlessly despite the malfunction that had delayed their landing several days previously.<ref name="fullsummary" /><ref name=lmjett/>

During the return to Earth, Mattingly performed an 83-minute EVA to retrieve film cassettes from the cameras in the SIM bay, with assistance from Duke who remained at the command module's hatch.<ref name="Drew">{{cite web |url=https://www.drewexmachina.com/2017/12/17/a-history-of-deep-space-evas/ |title=A History of Deep Space EVAs |last=LePage |first=Andrew |date=December 17, 2017 |website=Drew Ex Machina |access-date=November 6, 2019 |archive-date=February 20, 2022 |archive-url=https://web.archive.org/web/20220220193231/https://www.drewexmachina.com/2017/12/17/a-history-of-deep-space-evas/ |url-status=live }}</ref> At approximately {{convert|173,000|nmi|mi km}} from Earth, it was the second "deep space" EVA in history, performed at great distance from any planetary body. {{As of|{{year}}}}, it remains one of only three such EVAs, all performed during Apollo's J-missions under similar circumstances. During the EVA, Mattingly set up a biological experiment, the Microbial Ecology Evaluation Device (MEED),<ref name="mattinglyafj">{{cite web|url=https://history.nasa.gov/afj/ap16fj/27_Day10_Pt2.html|title=Apollo 16, Day 10 Part 2 – EVA and Housekeeping|work=Apollo 16 Flight Journal|editor-first=David|editor-last=Woods|editor2-first=Tim|editor2-last=Brandt|publisher=[[NASA]]|access-date=November 6, 2019|archive-date=December 31, 2020|archive-url=https://web.archive.org/web/20201231213255/https://history.nasa.gov/afj/ap16fj/27_Day10_Pt2.html|url-status=live}}</ref> an experiment unique to Apollo 16, to evaluate the response of microbes to the space environment.<ref name=meed>{{cite web|title=Microbial Ecology Evaluation Device (MEED)|url=http://lsda.jsc.nasa.gov/scripts/photoGallery/detail_result.aspx?image_id=2377|work=Life Sciences Data Archive|publisher=[[NASA]]|url-status=dead|archive-url=https://web.archive.org/web/20140407090048/http://lsda.jsc.nasa.gov/scripts/photoGallery/detail_result.aspx?image_id=2377|archive-date=April 7, 2014}}</ref> The crew carried out various housekeeping and maintenance tasks aboard the spacecraft and ate a meal before concluding the day.<ref name="mattinglyafj" />

The penultimate day of the flight was largely spent performing experiments, aside from a twenty-minute press conference during the second half of the day. During the press conference, the astronauts answered questions pertaining to several technical and non-technical aspects of the mission prepared and listed by priority at the [[Lyndon B. Johnson Space Center|Manned Spacecraft Center]] in Houston by journalists covering the flight. In addition to numerous housekeeping tasks, the astronauts prepared the spacecraft for its [[atmospheric entry|atmospheric reentry]] the next day. At the end of the crew's final full day in space, the spacecraft was approximately {{convert|77000|nmi|km|sp=us|order=flip}} from Earth and closing at a rate of about {{convert|7000|ft/s|km/s|sp=us|order=flip}}.<ref>{{cite web|title=Apollo 16: Day 11 Part One: Geology, Experiments and Guidance Fault Investigation|url=https://history.nasa.gov/ap16fj/28_Day11_Pt1.htm|work=Apollo 16 Flight Journal|archive-url=https://web.archive.org/web/20111021155831/http://history.nasa.gov/ap16fj/28_Day11_Pt1.htm|archive-date=October 21, 2011|date=May 15, 2008|url-status=dead|editor-first=David|editor-last=Woods|editor2-first=Tim|editor2-last=Brandt|publisher=[[NASA]]}}</ref><ref>{{cite web|title=Apollo 16: Day 11 Part Two: Press Conference, Experiments and House-Keeping|url=https://history.nasa.gov/ap16fj/29_Day11_Pt2.htm|work=Apollo 16 Flight Journal|archive-url=https://web.archive.org/web/20111021160421/http://history.nasa.gov/ap16fj/29_Day11_Pt2.htm|archive-date=October 21, 2011|date=May 11, 2008|url-status=dead|editor-first=David|editor-last=Woods|editor2-first=Tim|editor2-last=Brandt|publisher=[[NASA]]}}</ref>

When the wake-up call was issued to the crew for their final day in space by CAPCOM England, the CSM was about {{convert|45000|nmi|km}} from Earth, traveling just over {{convert|9000|ft/s|km/s|abbr=on|order=flip}}. Just over three hours before [[splashdown (spacecraft landing)|splashdown]] in the Pacific Ocean, the crew performed a final course correction burn, using the spacecraft's thrusters to change their velocity by {{convert|1.4|ft/s|m/s|abbr=on|order=flip}}. Approximately ten minutes before reentry into Earth's atmosphere, the cone-shaped command module containing the three crewmembers separated from the service module, which would burn up during reentry. At 265 hours and 37 minutes into the mission, at a velocity of about {{convert|36000|ft/s|km/s|abbr=on|order=flip}}, Apollo 16 began atmospheric reentry. At its maximum, the temperature of the heat shield was between {{convert|4000|and|4500|F|C|order=flip}}. After parachute deployment and less than 14 minutes after reentry began, the command module splashed down in the Pacific Ocean {{convert|189|nmi|km|sp=us|order=flip}} southeast of the island of [[Kiritimati]] 265 hours, 51 minutes, 5{{nbsp}}seconds after liftoff.<ref name="timeline" /> The spacecraft and its crew was retrieved by the aircraft carrier {{USS|Ticonderoga|CV-14|6}}. The astronauts were safely aboard the ''Ticonderoga'' 37 minutes after splashdown.<ref name="fullsummary" /><ref>{{cite web|title=Apollo 16: Day 12 – Entry and Splashdown|url= https://history.nasa.gov/afj/ap16fj/30_Day12.html#265_22_32 |work=Apollo 16 Flight Journal|archive-url= https://web.archive.org/web/20201128050530/https://history.nasa.gov/afj/ap16fj/30_Day12.html | archive-date = November 28, 2020 | url-status = live | date = Feb 11, 2020 |editor-first=David|editor-last=Woods|editor2-first=Tim|editor2-last=Brandt|publisher=[[NASA]]}}</ref>