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Pioneer 4 was an American spin-stabilized
uncrewed spacecraft Uncrewed spacecraft or robotic spacecraft are spacecraft without people on board. Uncrewed spacecraft may have varying levels of autonomy from human input, such as remote control, or remote guidance. They may also be autonomous, in which th ...
launched as part of the
Pioneer program The Pioneer programs were two series of United States lunar and planetary space probes. The first program, which ran from 1958 to 1960, unsuccessfully attempted to send spacecraft to orbit the Moon, successfully sent one spacecraft to fly by the ...
on a lunar flyby trajectory and into a
heliocentric orbit A heliocentric orbit (also called circumsolar orbit) is an orbit around the barycenter of the Solar System, which is usually located within or very near the surface of the Sun. All planets, comets, and asteroids in the Solar System, and the Sun ...
making it the first probe of the
United States The United States of America (USA), also known as the United States (U.S.) or America, is a country primarily located in North America. It is a federal republic of 50 U.S. state, states and a federal capital district, Washington, D.C. The 48 ...
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 The Geiger–Müller tube or G–M tube is the sensing element of the Geiger counter instrument used for the detection of ionizing radiation. It is named after Hans Geiger, who invented the principle in 1908, and Walther Müller, who collaborate ...
detector and a lunar photography experiment. It passed within of the
Moon The Moon is Earth's only natural satellite. It Orbit of the Moon, orbits around Earth at Lunar distance, an average distance of (; about 30 times Earth diameter, Earth's diameter). The Moon rotation, rotates, with a rotation period (lunar ...
's surface. However, ''Pioneer 4'' did not come close enough to trigger its photoelectric sensor. The spacecraft was still in solar orbit as of 1969. 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. After the Soviet
Luna 1 ''Luna 1'', also known as ''Mechta'' ( , ''Literal translation, lit.'': ''Dream''), ''E-1 No.4'' and ''First Lunar Rover'', was the first spacecraft to reach the vicinity of Earth's Moon, the first spacecraft to leave Earth's orbit, and the fi ...
probe conducted the first successful flyby of the Moon on 3 January 1959, the pressure felt by the US to succeed with a lunar mission was enormous, especially since American mission failures were entirely public while the Soviet failures were kept a secret.


Spacecraft design

''Pioneer 4'' was a cone-shaped probe 51 cm high and 23 cm in diameter at its base. The cone was composed of a thin
fiberglass Fiberglass (American English) or fibreglass (English in the Commonwealth of Nations, Commonwealth English) is a common type of fibre-reinforced plastic, fiber-reinforced plastic using glass fiber. The fibers may be randomly arranged, flattened i ...
shell coated with a gold wash to make it electrically conducting and painted with white stripes to maintain the temperature between 10 and 50 °C. At the tip of the cone was a small probe which combined with the cone itself to act as an antenna. At the base of the cone, a ring of
mercury batteries A mercury battery (also called mercuric oxide battery, mercury cell, button cell, or Ruben-Mallory) is a non-rechargeable battery (electricity), electrochemical battery, a primary cell. Mercury batteries use a reaction between mercuric oxide and ...
provided power. A photoelectric sensor protruded from the center of the ring. The sensor was designed with two photocells which would be triggered by the light of the Moon when the probe was within about 30,000 km of the Moon. At the center of the cone was a voltage supply tube and two
Geiger–Müller tube The Geiger–Müller tube or G–M tube is the sensing element of the Geiger counter instrument used for the detection of ionizing radiation. It is named after Hans Geiger, who invented the principle in 1908, and Walther Müller, who collaborate ...
s. The Laboratory's Microlock system, used for communicating with earlier Explorer satellites, did not have sufficient range to perform this mission. Therefore, a new radio system called TRAC(E) ''Tracking And Communication (Extraterrestrial)'' was designed. TRAC(E) was an integral part of the
Goldstone Deep Space Communications Complex The Goldstone Deep Space Communications Complex (GDSCC), commonly called the Goldstone Observatory, is a satellite ground station located in Fort Irwin in the U.S. state of California. Operated by NASA's Jet Propulsion Laboratory (JPL), its ...
. A transmitter with a mass of 0.5 kg delivered a phase modulated signal of 0.1 W at a frequency of 960.05 MHz. The modulated carrier power was 0.08 W and the total effective radiated power 0.18 W. A despin mechanism consisted of two 7 gram weights which spooled out to the end of two 150 cm wires when triggered by a hydraulic timer 10 hours after launch. The weights were designed to slow the spacecraft spin from 400 rpm to 6 rpm, and then weights and wires were released. Pioneer 4 received a few small modifications over its predecessor, namely added lead shielding around the Geiger tubes and modifications to the telemetry system to improve its reliability and signal strength. The probe had S/N #4, with probe #3 recalled from launch due to technical issues.


Launch vehicle

''Pioneer 4'' was launched with a Juno II launch vehicle, which also launched ''Pioneer 3''. Juno II closely resembled the Juno I (
Jupiter-C The Jupiter-C was an American research and development vehicle developed from the Jupiter-A. Jupiter-C was used for three Uncrewed vehicle, uncrewed sub-orbital spaceflights in 1956 and 1957 to test Re-entry vehicle, re-entry nosecones that were ...
based) vehicle that launched
Explorer 1 Explorer 1 was the first satellite launched by the United States in 1958 and was part of the U.S. participation in the International Geophysical Year (IGY). The mission followed the first two satellites, both launched by the Soviet Union duri ...
. Its first stage was a 19.51 m elongated
Jupiter Jupiter is the fifth planet from the Sun and the List of Solar System objects by size, largest in the Solar System. It is a gas giant with a Jupiter mass, mass more than 2.5 times that of all the other planets in the Solar System combined a ...
IRBM missile that was used by the U.S. Army. On top of the Jupiter propulsion section was a guidance and control compartment that supported a rotating tub containing the rocket stages 2, 3 and 4. ''Pioneer 4'' was mounted on top of stage 4.


Mission

At 05:10:56 GMT on the night of 3 March 1959, Pioneer 4 lifted off from LC-5 at
Cape Canaveral Cape Canaveral () is a cape (geography), cape in Brevard County, Florida, in the United States, near the center of the state's Atlantic Ocean, Atlantic coast. Officially Cape Kennedy from 1963 to 1973, it lies east of Merritt Island, separated ...
. This time, the booster performed almost perfectly so that ''Pioneer 4'' achieved its primary objective (an Earth-Moon trajectory), returned radiation data and provided a valuable tracking exercise. A slightly longer than nominal second stage burn, however, was enough to induce small trajectory and velocity errors, so that the probe passed within 58,983 km of the
Moon The Moon is Earth's only natural satellite. It Orbit of the Moon, orbits around Earth at Lunar distance, an average distance of (; about 30 times Earth diameter, Earth's diameter). The Moon rotation, rotates, with a rotation period (lunar ...
's surface (7.2° E, 5.7° S) on 4 March 1959 at 22:25 GMT (5:25 p.m. EST) at a speed of 7230 km/h. The distance was not close enough to trigger the photoelectric sensor. This scanning device was being tested for use in future probes to activate either a film or vidicon camera. The probe continued transmitting radiation data for 82.5 hours, to a distance of , and reached perihelion on 18 March 1959 at 01:00 GMT. The cylindrical fourth stage casing (173 cm long, 15 cm diameter, 4.65 kg) went into orbit with the probe. The communication system had worked well, and it was estimated that signals could have been received out to had there been enough battery power. File:Pioneer 4 von Braun inspection.jpg, The Pioneer 4 probe is inspected by (left to right) Dr. Wernher von Braun, payload engineer John Casani and Dr. James Van Allen. Pioneer-3-4.gif, Pioneer 4 Pioneer IV flight spare 02.jpg, Pioneer IV flight spare Juno II ignition with Pioneer 4.jpg, Launch of ''Pioneer 4'' 1959-03-05 Pioneer IV Passes Moon.ogg, Universal newsreel about the launch


See also

*
Luna 1 ''Luna 1'', also known as ''Mechta'' ( , ''Literal translation, lit.'': ''Dream''), ''E-1 No.4'' and ''First Lunar Rover'', was the first spacecraft to reach the vicinity of Earth's Moon, the first spacecraft to leave Earth's orbit, and the fi ...
– a similar
Soviet space program The Soviet space program () was the state space program of the Soviet Union, active from 1951 until the dissolution of the Soviet Union in 1991. Contrary to its competitors (NASA in the United States, the European Space Agency in Western Euro ...
mission launched 2 January 1959, several weeks before ''Pioneer 4''.


References


External links


NASA JPL ''Pioneer 3'' and ''4''

NSSDC Master Catalog: Spacecraft ''Pioneer 4''
{{Orbital launches in 1959 Spacecraft launched in 1959 Derelict satellites in heliocentric orbit Missions to the Moon Pioneer 04 Lunar flybys March 1959 in the United States