Apollo 7 in the context of Walter Cunningham

Sunlight is the portion of the electromagnetic radiation which is emitted by the Sun (i.e. solar radiation) and received by the Earth, in particular the visible light perceptible to the human eye as well as invisible infrared (typically perceived by humans as warmth) and ultraviolet (which can have physiological effects such as sunburn) lights. However, according to the American Meteorological Society, there are "conflicting conventions as to whether all three [...] are referred to as light, or whether that term should only be applied to the visible portion of the spectrum". Upon reaching the Earth, sunlight is scattered and filtered through the Earth's atmosphere as daylight when the Sun is above the horizon. When direct solar radiation is not blocked by clouds, it is experienced as sunshine, a combination of bright light and radiant heat (atmospheric). When blocked by clouds or reflected off other objects, sunlight is diffused. Sources estimate a global average of between 164 watts to 340 watts per square meter over a 24-hour day; this figure is estimated by NASA to be about a quarter of Earth's average total solar irradiance.

The ultraviolet radiation in sunlight has both positive and negative health effects, as it is both a requisite for vitamin D₃ synthesis and a mutagen.

As part of the Apollo program by NASA, 24 astronauts flew nine missions to the Moon between December 1968 and December 1972. During six successful two-man landing missions, twelve men walked on the lunar surface, six of whom drove Lunar Roving Vehicles as part of the last three missions. Three men have been to the Moon twice, one orbited once and took a circumlunar trajectory the second time, while the other two landed once apiece. Apart from these 24 men, no human being has gone beyond low Earth orbit. As of December 2025, five of the 24 remain alive. A number of non-human animals have circled or orbited it, including two tortoises, several turtles, and five mice.

Apollo missions 8 and 10–17 were the nine crewed missions to the Moon. Apollo 4–6 and AS-201 and AS-202 were uncrewed, while AS-203 is considered a test flight. The Apollo program included three other crewed missions: Apollo 1 (AS-204) did not launch and its crew died in a ground-based capsule fire, while Apollo 7 and Apollo 9 were low Earth orbit missions that tested spacecraft components and docking maneuvers. Apollo missions 18, 19, and 20 were canceled. Twelve astronauts later flew unused Apollo command modules in the Apollo Applications Program's Skylab and Apollo–Soyuz Test Project. Of the 24 astronauts who flew to the Moon, two went on to command a Skylab mission, one commanded Apollo–Soyuz, one flew as commander for Approach and Landing Tests of the Space Shuttle, and two commanded orbital Space Shuttle missions.

Eugene Andrew Cernan (/ˈsɜːrnən/; March 14, 1934 – January 16, 2017) was an American astronaut, naval aviator, electrical engineer, aeronautical engineer, and fighter pilot.

Cernan traveled into space three times and to the Moon twice: as pilot of Gemini 9A in June 1966, as lunar module pilot of Apollo 10 in May 1969, and as commander of Apollo 17 in December 1972, the final Apollo lunar landing. He was also a backup crew member of Gemini 12, Apollo 7, and Apollo 14. During the Apollo 17 mission, he became the 11th person to walk on the Moon as well as the astronaut with the longest time spent walking on the Moon; he is also the last person to walk on the Moon.

Apollo 8 (December 21–27, 1968) was the first crewed spacecraft to leave Earth's gravitational sphere of influence, and the first human spaceflight to reach the Moon. The crew orbited the Moon ten times without landing and then returned to Earth. The three astronauts—Frank Borman, Jim Lovell, and William Anders—were the first humans to see and photograph the far side of the Moon and an Earthrise.

Apollo 8 launched on December 21, 1968, and was the second crewed spaceflight mission flown in the United States Apollo space program (the first, Apollo 7, stayed in Earth orbit). Apollo 8 was the third flight and the first crewed launch of the Saturn V rocket. It was the first human spaceflight from the Kennedy Space Center, adjacent to Cape Kennedy Air Force Station in Florida.

Walter Marty Schirra Jr. (/ʃɜːˈrɑː/ shur-AH; March 12, 1923 – May 3, 2007) was an American naval aviator, test pilot, and NASA astronaut. In 1959, he became one of the original seven astronauts chosen for Project Mercury, which was the United States' first effort to put humans into space. On October 3, 1962, he flew the six-orbit, nine-hour, Mercury-Atlas 8 mission, in a spacecraft he nicknamed Sigma 7, becoming the fifth American and ninth human to travel into space. In December 1965, as part of the two-man Gemini program, he achieved the first space rendezvous, station-keeping his Gemini 6A spacecraft within 1 foot (30 cm) of the sister Gemini 7 spacecraft. In October 1968, he commanded Apollo 7, an 11-day low Earth orbit shakedown test of the three-man Apollo Command/Service Module and the first crewed launch for the Apollo program.

Before becoming an astronaut, Schirra graduated with a Bachelor of Science degree from the United States Naval Academy in 1945, and served at sea during World War II. In 1948, he became a naval aviator, served as a fighter pilot and flew 90 combat missions in the Korean War, and then in 1958 he graduated from the U.S. Naval Test Pilot School. Schirra retired from the Navy in 1969 with the rank of captain.

Donn Fulton Eisele (June 23, 1930 – December 1, 1987) (Colonel USAF) was a United States Air Force officer, test pilot, and later a NASA astronaut. He served as command module pilot for the Apollo 7 mission in 1968. After retiring from both NASA and the Air Force in 1972, he became the Peace Corps country director for Thailand, before moving into private business.

USS Essex (CV/CVA/CVS-9) was an aircraft carrier and the lead ship of the 24-ship Essex class built for the United States Navy during World War II. She was the fourth US Navy ship to bear the name. Commissioned in December 1942, Essex participated in several campaigns in the Pacific Theater of Operations, earning the Presidential Unit Citation and 13 battle stars. Decommissioned shortly after the war, she was modernized and recommissioned in the early 1950s as an attack carrier (CVA), eventually becoming an antisubmarine aircraft carrier (CVS). In her second career, she served mainly in the Atlantic, playing a role in the Cuban Missile Crisis. She also participated in the Korean War, earning four battle stars and the Navy Unit Commendation. She was the primary recovery carrier for the Apollo 7 space mission.

She was decommissioned for the last time in 1969 and sold by the Defense Reutilization and Marketing Service for scrap on 1 June 1973.