Apollo 10 Lunar Module Snoopy Passed 47,400 Feet Above Apollo 11 Site

Summary: Apollo 10 Lunar Module Snoopy passed 47,400 feet above Apollo 11 site 2, the site that edged out four contenders for the first human moon landing site.

North American Rockwell Corporation artist’s concept depicts Apollo 10 Lunar Module’s (center left) descent to 50,000 feet for a close look at Apollo 11 site 2, located in the east central lunar near side’s southwestern Mare Tranquillitatis (Sea of Tranquility), while the Command and Service Module (right) remains in lunar orbit; NASA image S69-30520: Generally not subject to copyright in the United States, via NASA Image and Digital Library

On Thursday, May 22, 1969, Apollo 10 Lunar Module Snoopy passed 47,400 feet above Apollo 11 site 2, favored as the prime landing site in July 1969 for the first human visitors to Earth’s moon.

Apollo 10 launched Sunday, May 18, 1969, at 16:49:00 Greenwich Mean Time/Coordinated Universal Time (11:49 p.m. Eastern Standard Time; 12:49 p.m. Eastern Daylight Time) from the National Aeronautics and Space Administration’s (NASA) Kennedy Space Center in central Florida. NASA’s Apollo 10 Press Kit, released Wednesday, May 7, 1969, described the mission as a “dress rehearsal” for Apollo 11 and noted: “Two Apollo 10 astronauts will descend to within eight nautical miles of the Moon’s surface, the closest man has ever been to another celestial body” (page 1).

NASA’s Press Kit also explained: “All aspects of Apollo 10 will duplicate conditions of the lunar landing mission as closely as possible -- Sun angles at Apollo Site 2, the out-and-back flight path to the Moon, and the time line of mission events. Apollo 10 differs from Apollo 11 in that no landing will be made on the Moon’s surface” (page 2).

NASA designated Thomas Patten Stafford (born Sept. 17, 1930) as commander of the Apollo 10 mission. John Watts Young (born Sept. 24, 1930) and Eugene Andrew Cernan (born March 14, 1934) crewed as command module pilot (CMP) and lunar module pilot (LMP), respectively.

The Apollo 10 spacecraft’s insertion into lunar orbit began with the service propulsion engine’s firing Wednesday, May 21, 1969, at 20:44:54 GMT/UTC (3:44 p.m. EST, 4:44 p.m. EDT), 75 hours 55 minutes 54.0 seconds (075:55:54.0 Ground Elapsed Time GET) after liftoff. At 095:02 GET (Thursday, May 22, at 15:51 UTC; 10:51 a.m. EST, 11:51 a.m. EDT), Commander Stafford and LMP Cernan entered Snoopy to activate the lunar module’s systems. The lunar module undocked from Command and Service Module (CSM) Charlie Brown at 098:11:57 GET (19:00:57 UTC; 2 p.m. EST; 3 p.m. EDT).

NASA’s Apollo 10 Press Kit stated that, among the lunar module’s objectives: “Some 800 seconds of landing radar altitude-measuring data will be gathered as the LM makes two sweeps eight nautical miles above Apollo Landing Site 2” (page 8).

Beginning at 099:46:01.6 GET (20:35:01 UTC; 3:35 p.m. EST, 4:35 p.m. EDT), the lunar module descent propulsion system (DPS) was fired for 27.4 seconds to achieve the lunar module’s descent orbit insertion (DOI) of 60.9 by 8.5 nautical miles. The lunar module made its closest approach to the lunar surface at 100:41:43 GET (21:30:43 UTC; 4:30 p.m. EST, 5:30 p.m. EDT). The low-level pass occurred about 15 degrees prior to Apollo 11 landing site 2, on the southwestern edge of Mare Tranquillitatis (Sea of Tranquility). The lunar module logged a pericynthion altitude of 47,400 feet (7.8 nautical miles) above the moon’s surface, according to freelance space writer Richard W. Orloff’s NASA-published history, Apollo by the Numbers (2000: page 76).

NASA’s Apollo 10 Post Launch Mission Operation Report, released May 26, 1969, detailed the accomplishments of the low-level pass: “Numerous photographs of the lunar surface were taken. Some camera malfunctions were reported and although some communications difficulties were experienced, the crew provided a continuous commentary of their observations. The LM landing radar test was executed during the low altitude pass over the surface” (page 4).

Beginning at 100:58:25.93 GET (21:47:25 UTC; 4:47 EST, 5:47 p.m. EDT), a 39.9-second phasing maneuver burn of the lunar module’s descent propulsion system (DPS) set a lead angle equivalent of a lunar landing’s powered ascent cutoff. The ignition placed Snoopy into an elliptical orbit of 190.1 by 12.1 nautical miles. The burn cut off at 100:59:05.88 GET (21:48:05 UTC; 4:48 p.m. EST, 5:48 p.m. EDT). According to NASA’s Apollo 10 Mission Report, the maneuver achieved the lunar module’s apocynthion altitude, farthest distance from the lunar surface, in a phasing orbit of about 8 by 194 nautical miles (1-1).

The three Apollo 10 astronauts splashed down at 192:03:23 GET (Tuesday, May 26, at 16:52:23 GMT; 11:52 p.m. EST, 12:52 p.m. EDT) in the central South Pacific Ocean, southeast of the U.S. Territory of American Samoa. From liftoff to splashdown, the astronauts had traveled an estimated distance of 721,250 nautical miles, according to Orloff’s Apollo by the Numbers (page 78).

NASA’s Apollo 10 Post Launch Mission Operation Report No. 1 gave the astronauts a stellar assessment. The report stated: “Flight crew performance was outstanding. All three crew members remained in excellent health throughout the mission. Their prevailing good spirits were continually evident as they took time from their busy schedule to share their voyage with the world via 19 color television transmissions totalling almost six hours” (page 7).

The takeaway for Apollo 10 Lunar Module Snoopy’s pass 47,400 feet above Apollo 11 site 2 is that the mission performed outstandingly as a “dress rehearsal” for NASA’s planned landing of two Apollo 11 astronauts on the lunar surface in July 1969.

TRW Incorporated artist’s concept depicts the 42-second Apollo 10 Lunar Module descent engine’s firing that propels Snoopy back into higher lunar orbit for rendezvous and docking with Command and Service Module Charlie Brown; NASA ID S69-33765: Generally not subject to copyright in the United States, via NASA Image and Digital Library

Acknowledgment

My special thanks to talented artists and photographers/concerned organizations who make their fine images available on the internet.

Image credits:

North American Rockwell Corporation artist’s concept depicts Apollo 10 Lunar Module’s (center left) descent to 50,000 feet for a close look at Apollo 11 site 2, located in the east central lunar near side’s southwestern Mare Tranquillitatis (Sea of Tranquility), while the Command and Service Module (right) remains in lunar orbit; NASA image S69-30520: Generally not subject to copyright in the United States; may use this material for educational or informational purposes, including photo collections, textbooks, public exhibits, computer graphical simulations and Internet Web pages; general permission extends to personal Web pages, via NASA Image and Digital Library @ https://images.nasa.gov/details-S69-30520

TRW Incorporated artist’s concept depicts the 42-second Apollo 10 Lunar Module descent engine’s firing that propels Snoopy back into higher lunar orbit for rendezvous and docking with Command and Service Module Charlie Brown; NASA ID S69-33765: Generally not subject to copyright in the United States; may use this material for educational or informational purposes, including photo collections, textbooks, public exhibits, computer graphical simulations and Internet Web pages; general permission extends to personal Web pages, via NASA Image and Digital Library @ https://images.nasa.gov/details-S69-33765

For further information:

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Available @ https://earth-and-space-news.blogspot.com/2014/05/apollo-10-imaged-near-sides-triesnecker.html

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Available @ https://earth-and-space-news.blogspot.com/2011/09/nick-howes-and-faulkes-telescope.html

Marriner, Derdriu. "Nick Howes Considers Possible Orbits for Apollo 10 Lunar Module Snoopy." Earth and Space News. Wednesday, Dec. 14, 2011.
Available @ https://earth-and-space-news.blogspot.com/2011/12/nick-howes-considers-possible-orbits_14.html

Marriner, Derdriu. “Snoopy and Charlie Brown Are Hugging Each Other in Apollo 10 Docking.” Earth and Space News. Wednesday, May 18, 2011.
Available @ https://earth-and-space-news.blogspot.com/2011/05/snoopy-and-charlie-brown-are-hugging.html

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Available @ https://history.nasa.gov/afj/ap10fj/pdf/a10-postlaunch-rep.pdf

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Available @ https://www.hq.nasa.gov/alsj/a410/A10_MissionReport.pdf

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