Pioneer 4
Encyclopedia
Pioneer 4 was a spin-stabilized
spacecraft launched as part of the Pioneer program
on a lunar flyby trajectory and into a heliocentric orbit
making it the first U.S. probe to escape from the Earth's gravity. 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 60,000 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 1969.
shell coated with a gold wash to make it electrically conducting and painted with white stripes to maintain the temperature between 10 and 50 degrees Celsius. 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
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
s. 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 IV was named Artificial Planet Two. Science News Letter March 14, 1959.
(Jupiter-C
based) vehicle that launched Explorer 1. Its first stage was a 19.51 m elongated Jupiter 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.
Spin-stabilisation
Spin-stabilisation is the method of stabilizing a satellite or launch vehicle by means of spin. For most satellite applications this approach has been superseded by three-axis stabilisation. It is also used in non-satellite applications such as rifle and artillery.Despinning can be achieved by...
spacecraft launched as part of the Pioneer program
Pioneer program
The Pioneer program is a series of United States unmanned space missions that was designed for planetary exploration. There were a number of such missions in the program, but the most notable were Pioneer 10 and Pioneer 11, which explored the outer planets and left the solar system...
on a lunar flyby trajectory and into a heliocentric orbit
Heliocentric orbit
A heliocentric orbit is an orbit around the Sun. All planets, comets, and asteroids in our Solar System are in such orbits, as are many artificial probes and pieces of debris. The moons of planets in the Solar System, by contrast, are not in heliocentric orbits as they orbit their respective planet...
making it the first U.S. probe to escape from the Earth's gravity. It carried a payload similar to Pioneer 3
Pioneer 3
Pioneer 3 was a spin stabilized spacecraft launched at 05:45:12 UTC on 6 December 1958 by the U.S. Army Ballistic Missile Agency in conjunction with the National Aeronautics and Space Administration...
: a lunar radiation environment experiment using a Geiger-Müller tube
Geiger-Müller tube
A Geiger–Müller tube is the sensing element of a Geiger counter instrument that can detect a single particle of ionizing radiation, and typically produce an audible click for each. It was named for Hans Geiger who invented the device in 1908, and Walther Müller who collaborated with Geiger in...
detector and a lunar photography experiment. It passed within 60,000 km of the Moon
Moon
The Moon is Earth's only known natural satellite,There are a number of near-Earth asteroids including 3753 Cruithne that are co-orbital with Earth: their orbits bring them close to Earth for periods of time but then alter in the long term . These are quasi-satellites and not true moons. For more...
's surface. However, Pioneer 4 did not come close enough to trigger its photoelectric sensor
Photoelectric sensor
A photoelectric sensor, or photoeye, is a device used to detect the distance, absence, or presence of an object by using a light transmitter, often infrared, and a photoelectric receiver. They are used extensively in industrial manufacturing. There are three different functional types: opposed ,...
. The spacecraft was still in solar orbit as of 1969.
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 fiberglassFiberglass
Glass fiber is a material consisting of numerous extremely fine fibers of glass.Glassmakers throughout history have experimented with glass fibers, but mass manufacture of glass fiber was only made possible with the invention of finer machine tooling...
shell coated with a gold wash to make it electrically conducting and painted with white stripes to maintain the temperature between 10 and 50 degrees Celsius. 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
Mercury battery
A mercury battery is a non-rechargeable electrochemical battery, a primary cell. Due to the content of mercury, and the resulting environmental concerns, the sale of mercury batteries is banned in many countries. Both ANSI and IEC have withdrawn standards for mercury batteries...
provided power. A photoelectric sensor
Photoelectric sensor
A photoelectric sensor, or photoeye, is a device used to detect the distance, absence, or presence of an object by using a light transmitter, often infrared, and a photoelectric receiver. They are used extensively in industrial manufacturing. There are three different functional types: opposed ,...
protruded from the center of the ring. The sensor was designed with two photocells
Photodetector
Photosensors or photodetectors are sensors of light or other electromagnetic energy. There are several varieties:*Active pixel sensors are image sensors consisting of an integrated circuit that contains an array of pixel sensors, each pixel containing a both a light sensor and an active amplifier...
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
Geiger-Müller tube
A Geiger–Müller tube is the sensing element of a Geiger counter instrument that can detect a single particle of ionizing radiation, and typically produce an audible click for each. It was named for Hans Geiger who invented the device in 1908, and Walther Müller who collaborated with Geiger in...
s. A transmitter with a mass of 0.5 kg delivered a phase modulated
Phase modulation
Phase modulation is a form of modulation that represents information as variations in the instantaneous phase of a carrier wave.Unlike its more popular counterpart, frequency modulation , PM is not very widely used for radio transmissions...
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.
Launching vehicle
Pioneer 4 was launched with a Juno II launching vehicle, which also launched Pioneer 3. Juno II closely resembled the Juno IJuno I
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...
(Jupiter-C
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....
based) vehicle that launched Explorer 1. Its first stage was a 19.51 m elongated Jupiter IRBM
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...
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
After a successful launch Pioneer 4 achieved its primary objective (an Earth-Moon trajectory), returned radiation data and provided a valuable tracking exercise. The probe passed within 60,000 km of the Moon's surface (7.2° E, 5.7° S) on 4 March 1959 at 22:25 UT (5:25 p.m. EST) at a speed of 7,230 km/h. The distance was not close enough to trigger the photoelectric sensor. The probe continued transmitting radiation data for 82.5 hours, to a distance of 658,000 km, and reached perihelion on 18 March 1959 at 01:00 UT. The cylindrical fourth stage casing (173 cm long, 15 cm diameter, 4.65 kg) went into orbit with the probe.See also
- Luna 1Luna 1Luna 1 , first known as First Cosmic Ship, then known as Mechta was the first spacecraft to reach the vicinity of the Moon and the first of the Luna program of Soviet automatic interplanetary stations successfully launched in the direction of the Moon.While traveling through the outer Van Allen...
- a similar Soviet space programSoviet space programThe Soviet space program is the rocketry and space exploration programs conducted by the former Union of Soviet Socialist Republics from the 1930s until its dissolution in 1991...
mission launched January 2, 1959, several weeks before Pioneer 4.