Explorer 2 was an American unmanned space mission within the Explorer program. Intended to be a repetition of the previous Explorer 1 mission, which placed a satellite into medium Earth orbit, the spacecraft was unable to reach orbit due to a failure in the launch vehicle during launch.
Explorer 35,, was a spin-stabilized spacecraft built by NASA as part of the Explorer program. It was designed for the study of the interplanetary plasma, magnetic field, energetic particles, and solar X-rays, from lunar orbit.
Explorer 6, or S-2, was a NASA satellite, launched on 7 August 1959, at 14:24:20 GMT. It was a small, spheroidal satellite designed to study trapped radiation of various energies, galactic cosmic rays, geomagnetism, radio propagation in the upper atmosphere, and the flux of micrometeorites. It also tested a scanning device designed for photographing the Earth's cloud cover. On 14 August 1959, Explorer 6 took the first photos of Earth from a satellite.
Explorer 11 was a NASA satellite that carried the first space-borne gamma-ray telescope. This marked the beginning of space gamma-ray astronomy. Launched on 27 April 1961 by a Juno II, the satellite returned data until 17 November 1961, when power supply problems ended the science mission. During the spacecraft's seven-month lifespan it detected twenty-two events from gamma-rays and approximately 22,000 events from cosmic radiation.
Explorer 7 was a NASA satellite launched on 13 October 1959, at 15:30:04 GMT, by a Juno II launch vehicle from Cape Canaveral Air Force Station (CCAFS) to an orbit of 573 × 1,073 km (356 × 667 mi) and inclination of 50.27°. It was designed to measure solar X-ray and Lyman-alpha flux, trapped energetic particles, and heavy primary cosmic rays. Secondary objectives included collecting data on micrometeoroid penetration, molecular sputtering and studying the Earth-atmosphere heat balance.
Explorer 5 was a United States satellite with a mass of 17.43 kg (38.4 lb). It was the last of the original series of Explorer satellites built, designed, and operated by the Jet Propulsion Laboratory.
Explorer 33, also known as IMP-D and AIMP-1, is a spacecraft in the Explorer program launched by NASA on 1 July 1966 on a mission of scientific exploration. It was the fourth satellite launched as part of the Interplanetary Monitoring Platform series, and the first of two "Anchored IMP" spacecraft to study the environment around Earth at lunar distances, aiding the Apollo program. It marked a departure in design from its predecessors, IMP-A through IMP-C. Explorer 35 was the companion spacecraft to Explorer 33 in the Anchored IMP program, but Explorer 34 (IMP-F) was the next spacecraft to fly, launching about two months before AIMP-E, both in 1967.
The Solar Anomalous and Magnetospheric Particle Explorer was a NASA solar and magnetospheric observatory, and was the first spacecraft in the Small Explorer program. It was launched into low Earth orbit on 3 July 1992, from Vandenberg Air Force Base aboard a Scout G-1 launch vehicle. SAMPEX was an international collaboration between NASA and the Max Planck Institute for Extraterrestrial Physics of Germany. The Solar Anomalous and Magnetospheric Particle Explorer (SAMPEX) is the first of a series of spacecraft that was launched under the Small Explorer (SMEX) program for low cost spacecraft.
Explorer 18, also called IMP-A, IMP-1, Interplanetary Monitoring Platform-1 and S-74, was a NASA satellite launched as part of the Explorer program. Explorer 18 was launched on 27 November 1963 from Cape Canaveral Air Force Station (CCAFS), Florida, with a Thor-Delta C launch vehicle. Explorer 18 was the first satellite of the Interplanetary Monitoring Platform (IMP). Explorer 21 (IMP-B) launched in October 1964 and Explorer 28 (IMP-C) launched in May 1965 also used the same general spacecraft design.
Explorer 14, also called EPE-B or Energetic Particles Explorer-B, was a NASA spacecraft instrumented to measure cosmic-ray particles, trapped particles, solar wind protons, and magnetospheric and interplanetary magnetic fields. It was the second of the S-3 series of spacecraft, which also included Explorer 12, 14, 15, and 26. It was launched on 2 October 1962, aboard a Thor-Delta launch vehicle.
Explorer 12, also called EPE-A or Energetic Particles Explorer-A and as S3), was a NASA satellite built to measure the solar wind, cosmic rays, and the Earth's magnetic field. It was the first of the S-3 series of spacecraft, which also included Explorer 12, 14, 15, and 26. It was launched on 16 August 1961, aboard a Thor-Delta launch vehicle. It ceased transmitting on 6 December 1961 due to power failure.
Explorer 26 was a NASA satellite launched on 21 December 1964, as part of NASA's Explorer program. Its primary mission was to study the Earth's magnetic field.
Explorer 28, also called IMP-C, IMP-3 and Interplanetary Monitoring Platform-3, was a NASA satellite launched on 29 May 1965 to study space physics, and was the third spacecraft launched in the Interplanetary Monitoring Platform program. It was powered by chemical batteries and solar panels. There were 7 experiments on board, all devoted to particle studies. Performance was normal until late April 1967, when intermittent problems began. It stayed in contact until 12 May 1967, when contact was lost. The orbit decayed until it re-entered the atmosphere on 4 July 1968. The spacecraft design was similar to its predecessors Explorer 18 (IMP-A), launched in November 1963, and Explorer 21 (IMP-B), launched in October 1964, though this satellite was a few kilograms lighter. The successor Explorer 33 (IMP-D) began the use of a new design.
Explorer S-46 was a NASA satellite with a mass of 41 kg (90 lb). It was the last of the original series of Explorer satellites built, designed, and operated by the Jet Propulsion Laboratory and Army Ballistic Missile Agency (ABMA).
Explorer 15, also called EPE-C or Energetic Particles Explorer-C, was a NASA satellite launched as part of the Explorer program. Explorer 15 was launched on 27 October 1962, at Cape Canaveral Air Force Station, Florida, United States, with a Thor-Delta A.
Explorer 21, also called IMP-B, IMP-2 and Interplanetary Monitoring Platform-2, was a NASA satellite launched as part of Explorer program. Explorer 21 was launched on 4 October 1964, at 03:45:00 GMT from Cape Canaveral (CCAFS), Florida, with a Thor-Delta C launch vehicle. Explorer 21 was the second satellite of the Interplanetary Monitoring Platform, and used the same general design as its predecessor, Explorer 18 (IMP-A), launched the previous year, in November 1963. The following Explorer 28 (IMP-C), launched in May 1965, also used a similar design.
Explorer 25, was a NASA magnetically aligned satellite launched simultaneously with Explorer 24 (AD-B) using a Scout X-4 launch vehicle. This was NASA's first dual-satellite launch. The satellite's primary mission was to make measurements of the influx of energetic particles into the atmosphere of Earth and to study atmospheric heating and the increase in scale height which have been correlated with geomagnetic activity. Studies of the natural and artificial trapped Van Allen radiation belts were also conducted. A biaxial fluxgate magnetometer was used to monitor the orientation of the spacecraft with respect to the local magnetic field.
Explorer 34, was a NASA satellite launched as part of Explorer program. Explorer 34 as launched on 24 May 1967 from Vandenberg Air Force Base, California, with Thor-Delta E1 launch vehicle. Explorer 34 was the fifth satellite launched as part of the Interplanetary Monitoring Platform program, but was known as "IMP-4" because the preceding launch was more specifically part of the "Anchored IMP" sub-program. The spacecraft was put into space between the launches of Explorer 33 in 1966 and Explorer 35 in July 1967, but the next satellite to use Explorer 34's general design was Explorer 41, which flew in 1969.
Explorer 41, also called as IMP-G and IMP-5, was a NASA satellite launched as part of Explorer program. Explorer 41 as launched on 21 June 1969 on Vandenberg AFB, California, with a Thor-Delta E1 launch vehicle. Explorer 41 was the seventh satellite launched as part of the overall Interplanetary Monitoring Platform series, though it received the post-launch designation "IMP-5" because two previous flights had used the "AIMP" designation instead. It was preceded by the second of those flights, Explorer 35, launched in July 1967. Its predecessor in the strict IMP series of launches was Explorer 34, launched in May 1967, which shared a similar design to Explorer 41. The next launch was of an IMP satellite was Explorer 43 in 1971.
Elektron ('electron'), in American sources sometimes called Electron, was the first Soviet multiple satellite program, comprising two identical pairs of particle physics satellites launched by the Soviet Union in 1964. The four spacecraft simultaneously monitored the lower and upper Van Allen radiation belts and returned a considerable volume of data regarding radiation in space and atmospheric conditions to an altitude of more than 58,000 kilometres (36,000 mi) above the Earth. Two of the four launched satellites are still in orbit As of 2023, the other two having reentered.
