Explorer 2

Explorer 2

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Explorer 2 was to be a repeat of the Explorer 1 mission. However, due to a failure in the rocket during launch, the spacecraft did not reach orbit.

Explorer 2 was launched from Cape Canaveral Air Force Station
Cape Canaveral Air Force Station
Cape Canaveral Air Force Station is an installation of the United States Air Force Space Command's 45th Space Wing, headquartered at nearby Patrick Air Force Base. Located on Cape Canaveral in the state of Florida, CCAFS is the primary launch head of America's Eastern Range with four launch pads...

Cape Canaveral Air Force Station Launch Complex 26
Launch Complex 26 is a deactivated launch site at Cape Canaveral Air Force Station, Florida. LC-26 consisted of two pads, A and B. Pad A was used for the Jupiter-C and Juno I rockets, and was the launch site for Explorer 1, the United States' first satellite, in 1958. Pad B was used for Juno II...

 in Florida
Florida is a state in the southeastern United States, located on the nation's Atlantic and Gulf coasts. It is bordered to the west by the Gulf of Mexico, to the north by Alabama and Georgia and to the east by the Atlantic Ocean. With a population of 18,801,310 as measured by the 2010 census, it...

 on March 5, 1958 at 18:28 UTC, by a Jupiter-C
The Jupiter-C was an American sounding rocket used for three sub-orbital spaceflights in 1956 and 1957 to test re-entry nosecones that were later to be deployed on the more advanced PGM-19 Jupiter mobile missile....

 launch vehicle.
The Jupiter-C had its origins in the United States Army's Project Orbiter
Project Orbiter
Project Orbiter was a proposed United States spacecraft, an early competitor to Project Vanguard. It was jointly run by the United States Army and United States Navy. It was ultimately rejected by the Ad Hoc Committee on Special Capabilities, which selected Project Vanguard instead...

 in 1954. The project was canceled in 1955, when the decision was made to proceed with Project Vanguard
Project Vanguard
Project Vanguard was a program managed by the United States Naval Research Laboratory , which intended to launch the first artificial satellite into Earth orbit using a Vanguard rocket as the launch vehicle from Cape Canaveral Missile Annex, Florida....


Following the launch of the Soviet Sputnik 1
Sputnik 1
Sputnik 1 ) was the first artificial satellite to be put into Earth's orbit. It was launched into an elliptical low Earth orbit by the Soviet Union on 4 October 1957. The unanticipated announcement of Sputnik 1s success precipitated the Sputnik crisis in the United States and ignited the Space...

 on October 4, 1957, the Army Ballistic Missile Agency
Army Ballistic Missile Agency
The Army Ballistic Missile Agency was the agency formed to develop the US Army's first intermediate range ballistic missile. It was established at Redstone Arsenal on February 1, 1956 and commanded by Major General John B...

 (ABMA) was directed to proceed with the launching of a satellite using the Jupiter-C, which had already been flight-tested in nose-cone re-entry tests for the Jupiter IRBM (intermediate-range ballistic missile
Intermediate-range ballistic missile
An intermediate-range ballistic missile is a ballistic missile with a range of 3,000–5,500 km , between a medium-range ballistic missile and an intercontinental ballistic missile...

). Working closely together, ABMA and Jet Propulsion Laboratory
Jet Propulsion Laboratory
Jet Propulsion Laboratory is a federally funded research and development center and NASA field center located in the San Gabriel Valley area of Los Angeles County, California, United States. The facility is headquartered in the city of Pasadena on the border of La Cañada Flintridge and Pasadena...

 (JPL) completed the job of modifying the Jupiter-C and building Explorer 1 in 84 days.

Spacecraft design

Explorer 2 was equipped with a Geiger counter
Geiger counter
A Geiger counter, also called a Geiger–Müller counter, is a type of particle detector that measures ionizing radiation. They detect the emission of nuclear radiation: alpha particles, beta particles or gamma rays. A Geiger counter detects radiation by ionization produced in a low-pressure gas in a...

 for the purposes of detecting cosmic ray
Cosmic ray
Cosmic rays are energetic charged subatomic particles, originating from outer space. They may produce secondary particles that penetrate the Earth's atmosphere and surface. The term ray is historical as cosmic rays were thought to be electromagnetic radiation...

s. After Explorer 3
Explorer 3
Explorer 3 was an artificial satellite of the Earth, nearly identical to the first United States artificial satellite Explorer 1 in its design and mission...

, it was decided that the original Geiger counter had been overwhelmed by strong radiation coming from a belt of charged particles trapped in space by the Earth's magnetic field
Earth's magnetic field
Earth's magnetic field is the magnetic field that extends from the Earth's inner core to where it meets the solar wind, a stream of energetic particles emanating from the Sun...

 (see: Van Allen radiation belt
Van Allen radiation belt
The Van Allen radiation belt is a torus of energetic charged particles around Earth, which is held in place by Earth's magnetic field. It is believed that most of the particles that form the belts come from solar wind, and other particles by cosmic rays. It is named after its discoverer, James...

). Explorer 2 was also equipped with a wire grid array and an acoustic detector for the purpose of micrometeorite
A micrometeoroid is a tiny meteoroid; a small particle of rock in space, usually weighing less than a gram. A micrometeor or micrometeorite is such a particle that enters the Earth's atmosphere or falls to Earth.-Scientific interest:...


Mission results

Explorer 2 failed to reach orbit after a malfunction in the Jupiter-C launch vehicle caused the fourth stage to not ignite.