The Explorers program is a NASA exploration program that provides flight opportunities for physics, geophysics, heliophysics, and astrophysics investigations from space. Launched in 1958, Explorer 1 was the first spacecraft of the United States to achieve orbit. Over 90 space missions have been launched since. Starting with Explorer 6, it has been operated by NASA, with regular collaboration with a variety of other institutions, including many international partners.
Pioneer 3 was a spin-stabilized spacecraft launched at 05:45:12 GMT on 6 December 1958 by the U.S. Army Ballistic Missile Agency in conjunction with the NASA, using a Juno II rocket. This spacecraft was intended as a lunar probe, but failed to go past the Moon and into a heliocentric orbit as planned. It did however reach an altitude of 102,360 km before falling back to Earth. The revised spacecraft objectives were to measure radiation in the outer Van Allen radiation belt using two Geiger-Müller tubes and to test the trigger mechanism for a lunar photographic experiment.
Pioneer 4 was an American spin-stabilized uncrewed spacecraft launched as part of the Pioneer program on a lunar flyby trajectory and into a heliocentric orbit making it the first probe of the United States to escape from the Earth's gravity. Launched on March 3, 1959, it carried a payload similar to Pioneer 3: a lunar radiation environment experiment using a Geiger–Müller tube detector and a lunar photography experiment. It passed within 58,983 km of the Moon's surface. However, Pioneer 4 did not come close enough to trigger its photoelectric sensor. The spacecraft was still in solar orbit as of 2023. It was the only successful lunar probe launched by the U.S. in 12 attempts between 1958 and 1963; only in 1964 would Ranger 7 surpass its success by accomplishing all of its mission objectives.
A trans-lunar injection (TLI) is a propulsive maneuver used to set a spacecraft on a trajectory that will cause it to arrive at the Moon.
Luna 11 was an uncrewed space mission of the Soviet Union's Luna program. It was also called Lunik 11. Luna 11 was launched towards the Moon from an Earth-orbiting platform and entered lunar orbit on 27 August 1966.
Luna 14 was an unmanned space mission of the Luna program run by the Soviet Union. It was also called Lunik 14.
Luna 16 was an uncrewed space mission, part of the Soviet Luna program. It was the first robotic probe to land on the Moon and return a sample of lunar soil to Earth. The 101 grams sample was returned from Mare Fecunditatis. It represented the first successful lunar sample return mission by the Soviet Union and was the third lunar sample return mission overall.
Luna 18, part of the Ye-8-5 series, was an unmanned space mission of the Luna program.
The Lunar Orbiter program was a series of five uncrewed lunar orbiter missions launched by the United States from 1966 through 1967. Intended to help select Apollo landing sites by mapping the Moon's surface, they provided the first photographs from lunar orbit and photographed both the Moon and Earth.
Surveyor 5 was the fifth lunar lander of the American uncrewed Surveyor program sent to explore the surface of the Moon. Surveyor 5 landed on Mare Tranquillitatis in 1967. A total of 19,118 images were transmitted to Earth.
The 1966 Lunar Orbiter 1 robotic spacecraft mission, part of NASA's Lunar Orbiter program, was the first American spacecraft to orbit the Moon. It was designed primarily to photograph smooth areas of the lunar surface for selection and verification of safe landing sites for the Surveyor and Apollo missions. It was also equipped to collect selenodetic, radiation intensity, and micrometeoroid impact data.
The 1966 Lunar Orbiter 2 robotic spacecraft mission, part of the Lunar Orbiter Program, was designed primarily to photograph smooth areas of the lunar surface for selection and verification of safe landing sites for the Surveyor and Apollo missions. It was also equipped to collect selenodetic, radiation intensity, and micrometeoroid impact data.
The Lunar Orbiter 3 was a spacecraft launched by NASA in 1967 as part of the Lunar Orbiter Program. It was designed primarily to photograph areas of the lunar surface for confirmation of safe landing sites for the Surveyor and Apollo missions. It was also equipped to collect selenodetic, radiation intensity, and micrometeoroid impact data.
Lunar Orbiter 5, the last of the "Lunar Orbiter series", was designed to take additional Apollo and Surveyor landing site photography and to take broad survey images of unphotographed parts of the Moon's far side. It was also equipped to collect selenodetic, radiation intensity, and micrometeoroid impact data and was used to evaluate the Manned Space Flight Network tracking stations and Apollo Orbit Determination Program.
Discoverer 20, also known as KH-5 9014A, was a USAF photographic reconnaissance satellite under the supervision of the National Reconnaissance Office (NRO) which was launched in 1961. Discoverer 20 was the first KH-5 ARGON satellite to be launched.
Chang'e 5-T1 was an experimental robotic spacecraft that was launched to the Moon on 23 October 2014 by the China National Space Administration (CNSA) to conduct atmospheric re-entry tests on the capsule design planned to be used in the Chang'e 5 mission. As part of the Chinese Lunar Exploration Program, Chang'e 5, launched in 2020, was a Moon sample return mission. Like its predecessors, the spacecraft is named after the Chinese Moon goddess Chang'e. The craft consisted of a return vehicle capsule and a service module orbiter.
Kosmos 159, E-6LS No.111, was one of many satellites designed during the Soviet space program given the designation Kosmos. This satellite was specifically designed to be a high orbit satellite used to gain information on trajectory anomalies caused by the Moon's gravitational pull. This data would have been vital to the Soviet space program and could have been key in successful crewed missions to the Moon. This mission was also used to test radio communications in space.
Kosmos 146, also known as L-1 No. 2P, was a Soviet test spacecraft precursor to the Zond series, launched from the Baikonur Cosmodrome aboard a Proton K rocket.
Small Innovative Missions for Planetary Exploration (SIMPLEx) is a planetary exploration program operated by NASA. The program funds small, low-cost spacecraft for stand-alone planetary exploration missions. These spacecraft are intended to launch as secondary payloads on other missions and are riskier than Discovery or New Frontiers missions.
