Explorer 3

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Explorer 3
Explorer1.jpg
Photograph of the nearly identical Explorer 1
Mission type Earth science
Operator Army Ballistic Missile Agency (ABMA)
Harvard designation1958 Gamma 1
COSPAR ID 1958-003A
SATCAT no. 00006
Mission duration93 days
Spacecraft properties
Manufacturer Jet Propulsion Laboratory
Launch mass14.1 kilograms (31 lb)
Start of mission
Launch dateMarch 26, 1958, 17:31 (1958-03-26UTC17:31Z) UTC
Rocket Juno I RS-24
Launch site Cape Canaveral LC-5
End of mission
Decay dateJune 27, 1958 (1958-06-28)
Orbital parameters
Reference system Geocentric
Regime Medium Earth
Semi-major axis 7,870.7 kilometers (4,890.6 mi)
Eccentricity 0.165894
Perigee 186 kilometers (116 mi)
Apogee 2,799 kilometers (1,739 mi)
Inclination 33.38 degrees
Period 115.7 minutes
Epoch 26 March 1958
Explorer program

Explorer 3 (international designation 1958 Gamma) 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 the second successful launch in the Explorer program.

Satellite Human-made object put into an orbit

In the context of spaceflight, a satellite is an artificial object which has been intentionally placed into orbit. Such objects are sometimes called artificial satellites to distinguish them from natural satellites such as Earth's Moon.

Earth Third planet from the Sun in the Solar System

Earth is the third planet from the Sun and the only astronomical object known to harbor life. According to radiometric dating and other sources of evidence, Earth formed over 4.5 billion years ago. Earth's gravity interacts with other objects in space, especially the Sun and the Moon, Earth's only natural satellite. Earth revolves around the Sun in 365.26 days, a period known as an Earth year. During this time, Earth rotates about its axis about 366.26 times.

United States Federal republic in North America

The United States of America (USA), commonly known as the United States or America, is a country composed of 50 states, a federal district, five major self-governing territories, and various possessions. At 3.8 million square miles, the United States is the world's third or fourth largest country by total area and is slightly smaller than the entire continent of Europe's 3.9 million square miles. With a population of over 327 million people, the U.S. is the third most populous country. The capital is Washington, D.C., and the largest city by population is New York City. Forty-eight states and the capital's federal district are contiguous in North America between Canada and Mexico. The State of Alaska is in the northwest corner of North America, bordered by Canada to the east and across the Bering Strait from Russia to the west. The State of Hawaii is an archipelago in the mid-Pacific Ocean. The U.S. territories are scattered about the Pacific Ocean and the Caribbean Sea, stretching across nine official time zones. The extremely diverse geography, climate, and wildlife of the United States make it one of the world's 17 megadiverse countries.

Contents

Mission

The satellite was launched from Cape Canaveral Air Force Station, Florida at 17:31:00 UTC on March 26, 1958, by the Juno I vehicle. [1] The Juno I had its origins in the United States Army's Project Orbiter in 1954. The project was canceled in 1955, however, when the decision was made to proceed with Project Vanguard.

Cape Canaveral Air Force Station spaceport on Cape Canaveral, USA

Cape Canaveral Air Force Station (CCAFS) is an installation of the United States Air Force Space Command's 45th Space Wing.

Florida State of the United States of America

Florida is the southernmost contiguous state in the United States. The state is bordered to the west by the Gulf of Mexico, to the northwest by Alabama, to the north by Georgia, to the east by the Atlantic Ocean, and to the south by the Straits of Florida. Florida is the 22nd-most extensive, the 3rd-most populous, and the 8th-most densely populated of the U.S. states. Jacksonville is the most populous municipality in the state and the largest city by area in the contiguous United States. The Miami metropolitan area is Florida's most populous urban area. Tallahassee is the state's capital.

The Juno I was a four-stage American booster rocket which launched America's first satellite, Explorer 1, in 1958. A member of the Redstone rocket family, it was derived from the Jupiter-C sounding rocket. It is commonly confused with the Juno II launch vehicle, which was derived from the PGM-19 Jupiter medium-range ballistic missile.

Following the launch of the Soviet Sputnik 1 on October 4, 1957, Army Ballistic Missile Agency (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). Working closely together, ABMA and JPL completed the job of modifying the Jupiter-C to the Juno I and building the Explorer I in 84 days.

Sputnik 1 first artificial Earth satellite

Sputnik 1 was the first artificial Earth satellite. The Soviet Union launched it into an elliptical low Earth orbit on 4 October 1957, orbiting for three weeks before its batteries died, then silently for two more months before falling back into the atmosphere. It was a 58 cm (23 in) diameter polished metal sphere, with four external radio antennas to broadcast radio pulses. Its radio signal was easily detectable even by radio amateurs, and the 65° inclination and duration of its orbit made its flight path cover virtually the entire inhabited Earth. This surprise success precipitated the American Sputnik crisis and triggered the Space Race, a part of the Cold War. The launch was the beginning of a new era of political, military, technological, and scientific developments.

Army Ballistic Missile Agency US agency

The Army Ballistic Missile Agency (ABMA) was formed to develop the U.S. Army's first large ballistic missile. The agency was established at Redstone Arsenal on 1 February 1956, and commanded by Major General John B. Medaris with Wernher von Braun as technical director.

PGM-19 Jupiter ballistic missile

The PGM-19 Jupiter was the first nuclear tipped, medium-range ballistic missile (MRBM) of the United States Air Force (USAF). It was a liquid-propellant rocket using RP-1 fuel and LOX oxidizer, with a single Rocketdyne LR70-NA rocket engine producing 667 kN of thrust. It was armed with the 1.44 megaton W49 nuclear warhead. The prime contractor was the Chrysler Corporation.

Spacecraft design

Explorer 3 Flight Recorder Explorer 3 Flight Recorder.jpg
Explorer 3 Flight Recorder

Explorer 3 was launched in conjunction with the International Geophysical Year (IGY) by the U.S. Army (Ordnance) into an eccentric orbit. The objective of this spacecraft was a continuation of experiments started with Explorer 1. The payload consisted of a cosmic ray counter (a Geiger-Müller tube), and a micrometeorite detector (a wire grid array and acoustic detector). The Explorer 3 spacecraft was spin-stabilized and had an on-board tape recorder to provide a complete radiation history for each orbit. It was discovered soon after launch that the satellite was in a tumbling motion with a period of about 7 seconds. Explorer 3 decayed from orbit on June 27, 1958, after 93 days of operation.

International Geophysical Year science-cooperation year of 1957-1958

The International Geophysical Year was an international scientific project that lasted from July 1, 1957, to December 31, 1958. It marked the end of a long period during the Cold War when scientific interchange between East and West had been seriously interrupted. Sixty-seven countries participated in IGY projects, although one notable exception was the mainland People's Republic of China, which was protesting against the participation of the Republic of China (Taiwan). East and West agreed to nominate the Belgian Marcel Nicolet as secretary general of the associated international organization.

Orbital eccentricity parameter that determines the amount by which an orbit deviates from a perfect circle

The orbital eccentricity of an astronomical object is a parameter that determines the amount by which its orbit around another body deviates from a perfect circle. A value of 0 is a circular orbit, values between 0 and 1 form an elliptic orbit, 1 is a parabolic escape orbit, and greater than 1 is a hyperbola. The term derives its name from the parameters of conic sections, as every Kepler orbit is a conic section. It is normally used for the isolated two-body problem, but extensions exist for objects following a Klemperer rosette orbit through the galaxy.

Cosmic ray High-energy particle, mainly originating outside the Solar system

Cosmic rays are high-energy radiation, mainly originating outside the Solar System and even from distant galaxies. Upon impact with the Earth's atmosphere, cosmic rays can produce showers of secondary particles that sometimes reach the surface. Composed primarily of high-energy protons and atomic nuclei, they are originated either from the sun or from outside of our solar system. Data from the Fermi Space Telescope (2013) have been interpreted as evidence that a significant fraction of primary cosmic rays originate from the supernova explosions of stars. Active galactic nuclei also appear to produce cosmic rays, based on observations of neutrinos and gamma rays from blazar TXS 0506+056 in 2018.

Mission results

The discovery of the Van Allen radiation belt by the Explorer satellites was considered to be one of the outstanding discoveries of the IGY.

Van Allen radiation belt Zone of energetic charged particles around the planet earth

A Van Allen radiation belt is a zone of energetic charged particles, most of which originate from the solar wind, that are captured by and held around a planet by that planet's magnetic field. Earth has two such belts and sometimes others may be temporarily created. The discovery of the belts is credited to James Van Allen, and as a result, Earth's belts are known as the Van Allen belts. Earth's two main belts extend from an altitude of about 640 to 58,000 km above the surface in which region radiation levels vary. Most of the particles that form the belts are thought to come from solar wind and other particles by cosmic rays. By trapping the solar wind, the magnetic field deflects those energetic particles and protects the atmosphere from destruction.

Explorer 3 was placed in an orbit with a perigee of 186 kilometers and an apogee of 2799 kilometers having a period of 115.7 minutes. Its total weight was 14.1 kilograms, of which 8.4 kg was instrumentation. The instrument section at the front end of the satellite and the empty scaled-down fourth-stage rocket casing orbited as a single unit, spinning around its long axis at 750 revolutions per minute.

MGM-29 Sergeant short range surface-to-surface missile

The MGM-29 Sergeant was an American short-range, solid fuel, surface-to-surface missile developed at the Jet Propulsion Laboratory. The missiles were built by Sperry Utah Company. The Sergeant was the fourth and last in a series of JPL rockets for the US Army whose names correspond to the progression in Army enlisted ranks, starting with Recruit, Private and Corporal.

Instrumentation consisted of a cosmic ray detection package and a ring of micrometeorite erosion gauges. The Explorer 3 spacecraft was spin-stabilized and had an on-board tape recorder to provide a complete radiation history for each orbit. Data from these instruments was transmitted to the ground by a 60 milliwatt transmitter operating on 108.03 MHz and a 10 milliwatt transmitter operating on 108.00 MHz.

Transmitting antennas consisted of two fiberglass slot antennas in the body of the satellite itself. The four flexible whip antennas of Explorer 1 were removed from the design. [2]

The external skin of the instrument section was painted in alternate strips of white and dark green to provide passive temperature control of the satellite. The proportions of the light and dark strips were determined by studies of shadow-sunlight intervals based on firing time, trajectory, orbit, and inclination.

Electrical power was provided by Mallory type RM Mercury cells that made up approximately 40 percent of the payload weight. These provided power that operated the high power transmitter for 31 days and the low-power transmitter for 105 days.

Because of the limited space available and the requirements for low weight, the Explorer 3 instrumentation was designed and built with simplicity and high reliability in mind. It was completely successful.

Explorer 3 decayed from orbit on June 27, 1958, after 93 days of operation.

A replica of the spacecraft is currently located in the Smithsonian Institution's National Air and Space Museum, Milestones of Flight Gallery.

See also

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References

  1. "About the Mission". JPL. Retrieved June 24, 2017.
  2. Pilkington, W. C. (September 5, 1958). "Vehicle Motions as Inferred from Radio-signal- Strength Records". JPL. Retrieved October 18, 2018.