Editing Apollo 10 (section)

====The flight of ''Snoopy''====
[[File:AS10-34-5158 - Apollo 10 - Apollo 10 Mission image - Landing Site 2 - NARA - 16682380.jpg|thumb|right|Photograph of ALS-2 taken by Apollo 10]]
After Stafford and Cernan checked out ''Snoopy'', they returned to ''Charlie Brown'' for a rest. Then they re-entered ''Snoopy'' at 95:02 and undocked it from the CSM three hours later at 98:11:57.{{sfn|Orloff|2004|pp=72–79}} Young, who remained in the CSM, became the first person to fly solo in lunar orbit.<ref name="Neal">{{Cite news |last=Neal |first=Valerie |date=January 19, 2018 |title=John W. Young, an Astronaut's Astronaut (1930-2018) |url=https://airandspace.si.edu/stories/editorial/john-w-young-astronaut-1930-2018 |access-date=July 2, 2022 |publisher=[[National Air and Space Museum]]}}</ref> After undocking, Stafford and Cernan deployed the LM's landing gear and inspected the LM's systems. About 35 minutes after the initial separation, the CSM performed an 8.3-second burn with its RCS thrusters to separate itself from the LM by about {{Convert|30|ft}}, after which Young visually inspected the LM from the CSM. The CSM performed another separation burn, this time separating the two spacecraft by about {{convert|2|nmi|km|abbr=off|disp=out|sp=us}} (2&nbsp;nautical&nbsp;miles; {{convert|2|nmi|mi|abbr=off|disp=out}}).{{sfn|Orloff|2004|pp=72–79}} The LM crew then performed the descent orbit insertion maneuver by firing their descent engine for 27.4 seconds at 99:46:01.6, and tested their craft's landing radar as they approached the {{convert|50000|ft|m|adj=on|abbr=off|sp=us|order=flip}} altitude where the subsequent Apollo 11 mission would begin powered descent to land on the Moon.{{sfn|Orloff & Harland|pp=259–260}} Previously, the LM's landing radar had only been tested under terrestrial conditions.{{sfn|Press Kit|p=8}} While the LM executed these maneuvers, Young monitored the location and status of the LM from the CSM, standing by to rescue the LM crew if necessary.{{sfn|Chaikin|p=158}} Cernan and Stafford surveyed ALS-2, coming within {{convert|8.4|nmi|km|abbr=off|disp=out|sp=us}} (8.4&nbsp;nautical&nbsp;miles; {{convert|8.4|nmi|mi|abbr=off|disp=out}}) of the surface at a point 15 degrees to its east, then performed a phasing burn at 100:58:25.93, thrusting for just under 40 seconds to allow a second pass at ALS-2, when the craft came within {{convert|7.8|nmi|km|abbr=off|disp=out|sp=us}} (7.8&nbsp;nautical&nbsp;miles; {{convert|7.8|nmi|mi|abbr=off|disp=out|0}}) of the Moon, its closest approach.{{sfn|Orloff & Harland|pp=259–260}} Reporting on his observations of the site from the LM's low passes, Stafford indicated that ALS-2 seemed smoother than he had expected{{sfn|Chaikin|p=158}} and described its appearance as similar to the desert surrounding [[Blythe, California]];{{sfn|Wilhelms|p=191}} but he observed that Apollo 11 could face rougher terrain downrange if it approached off-target.{{sfn|Chaikin|p=158}} Based upon Apollo 10's observations from relatively low altitude, NASA mission planners became comfortable enough with ALS-2 to confirm it as the target site for Apollo 11.{{sfn|Wilhelms|p=192}}

[[File:AS10-34-5087.jpg|thumb|left|LM ''Snoopy'' containing Stafford and Cernan, as inspected by Young after separation from ''Charlie Brown'']]
The next action was to prepare to separate the LM ascent stage from the descent stage, to jettison the descent stage, and fire the [[Ascent Propulsion System]] to return the ascent stage towards the CSM. As Stafford and Cernan prepared to do so, the LM began to gyrate out of control.{{sfn|Chaikin|p=159}} Alarmed, Cernan exclaimed, "Son of a bitch!" into a [[hot mic]] being broadcast live, which, combined with other language used by the crew during the mission, generated some complaints back on Earth.<ref>{{Cite news |last=Simmons |first=Roger |date=May 28, 2019 |title=Foul-mouthed Apollo astronauts got space program in trouble 50 years ago |url=https://www.orlandosentinel.com/space/apollo-11-anniversary/os-ne-apollo-11-cursing-astronautps-20190528-xpfrowxpdve37acs4kbsnn43fe-story.html |access-date=June 26, 2022 |work=[[Orlando Sentinel]]}}</ref> Stafford discarded the descent stage about five seconds after the tumbling began{{sfn|Orloff|2004|pp=72–79}} and fought to regain control manually, suspecting that there might have been an "open thruster", or a thruster stuck firing.{{sfn|Cernan|p=218}} He did so in time to orient the spacecraft to rejoin ''Charlie Brown''.{{sfn|Chaikin|p=159}} The problem was traced to a switch controlling the mode of the abort guidance system; it was to be moved as part of the procedure, but both of the crew members switched it, thus returning it to the original position. Had they fired ''Snoopy'' in the wrong direction, they might have missed the rendezvous with ''Charlie Brown'' or crashed into the Moon.{{sfn|French & Burgess|pp=1385–1391}} Once Stafford had regained control of the LM ascent stage, which took about eight seconds,{{sfn|Chaikin|p=159}} the pair fired the ascent engine at the lowest point of the LM's orbit, mimicking the [[orbital insertion]] maneuver after launch from the lunar surface in a later landing mission. ''Snoopy'' coasted on that trajectory for about an hour before firing the engine once more to further fine-tune its approach to ''Charlie Brown''.{{sfn|Orloff|2004|pp=72–79}}

[[File:Apollo 10 Earthrise.ogv|thumb|right|Earthrise video captured by Apollo 10 crew]]
''Snoopy'' rendezvoused with and re-docked with ''Charlie Brown'' at 106:22:02, just under eight hours after undocking.{{sfn|Orloff|2004|pp=72–79}} The docking was telecast live in color from the CSM.<ref>{{Cite web |last=Gohd |first=Chelsea |date=May 18, 2019 |title=Snoopy to the Moon! Apollo 10 Commander Looks Back on Historic Flight 50 Years Ago |url=https://www.space.com/apollo-10-commander-thomas-stafford-memories-50th-anniversary.html |access-date=June 26, 2022 |publisher=[[Space.com]] |language=en}}</ref><ref>{{Cite web |date=April 15, 2022 |title=John Young: Not just the commander of Apollo 16 |url=https://universemagazine.com/en/john-young-not-just-the-commander-of-apollo-16/ |access-date=June 26, 2022 |magazine=Universe Magazine}}</ref> Once Cernan and Stafford had re-entered ''Charlie Brown'', ''Snoopy'' was sealed off and separated from ''Charlie Brown.'' The rest of the LM's ascent-stage engine fuel was burned to send it on a trajectory past the Moon and into a [[heliocentric orbit]].<ref name="nasa_apollo10">{{Cite web |date=July 8, 2009 |editor-last=Ryba |editor-first=Jeanne |title=Apollo 10 |url=http://www.nasa.gov/mission_pages/apollo/missions/apollo10.html |access-date=June 26, 2013 |publisher=NASA}}</ref><ref name="disposition">{{Cite web |title=Current locations of the Apollo Command Module Capsules (and Lunar Module crash sites) |url=http://nssdc.gsfc.nasa.gov/planetary/lunar/apolloloc.html |access-date=27 December 2014 |website=Apollo: Where are they now? |publisher=NASA}}</ref>

It was the only Apollo LM to meet this fate. The Apollo 11 ascent stage would be left in lunar orbit to crash randomly, while ascent stages of later Apollo mission (12, 14, 15 and 17) were steered into the Moon to obtain readings from [[seismometers]] placed nearby on the surface, with two exceptions: Apollo 13's ascent stage, which the crew used as a "life boat" to get safely back to Earth before releasing it to burn up in Earth's atmosphere, and [[Apollo 16]]'s, which NASA lost control of after jettison.<ref name="disposition" />