Pioneer III

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 US probe to escape from the Earth's gravity. It carried a payload similar to Pioneer 3: a lunar radiation environment experiment using a Geiger-Mueller 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 the photoelectric sensor. No lunar radiation was detected. The spacecraft was still in solar orbit as of 1969. Pioneer 3 NASA Center: Jet Propulsion Laboratory Image # : 314-3944b Date : 01/01/1961 Title Pioneer III Probe Full Description Looking more like surgeons, these technicians wearing cleanroom attire inspect the Pioneer III probe before shipping it to Cape Canaveral, Florida. ... Pioneer 3 NASA Center: Jet Propulsion Laboratory Image # : 314-3944b Date : 01/01/1961 Title Pioneer III Probe Full Description Looking more like surgeons, these technicians wearing cleanroom attire inspect the Pioneer III probe before shipping it to Cape Canaveral, Florida. ... The American Pioneer program of unmanned space missions was designed for planetary exploration. ... In astronomy, heliocentrism is the theory that the Sun is at the center of the Universe and/or the Solar System. ... Pioneer III Pioneer 3 was a spin stabilized spacecraft launched by the U.S. Army Ballistic Missile agency in conjunction with NASA. The spacecraft was intended as a lunar probe, but failed to go past the Moon and into a heliocentric orbit as planned, but did reach an altitude of... 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. ... Crust composition Oxygen 43% Silicon 21% Aluminium 10% Calcium 9% Iron 9% Magnesium 5% Titanium 2% Nickel 0. ... 1969 was a common year starting on Wednesday (the link is to a full 1969 calendar). ...

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 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 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 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-Mueller tubes. 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. Glass-reinforced plastic (GRP), is a composite material or fibre reinforced plastic made of a plastic reinforced by fine fibers made of glass. ... A photoresistor is an electronic component whose resistance decreases with increasing incident light intensity. ...

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 hours, to a distance of 658,000 km ₁, 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. The Radiation Belt and Magnetosphere is a book written by Wilmot Hess in 1968. ...

External Links

• NASA JPL Pioneer 3 & 4 (http://www.jpl.nasa.gov/missions/past/pioneer.html)
• NSSDC Master Catalog: Spacecraft Pioneer 4 (http://nssdc.gsfc.nasa.gov/nmc/tmp/1959-013A.html)

References

1. The Radiation Belt and Magnetosphere by Wilmot Hess (1968)

The Radiation Belt and Magnetosphere is a book written by Wilmot Hess in 1968. ... Wilmot N. Hess is a retired Associate Director of the US Department of Energy, first elected in 1976. ... 1968 was a leap year starting on Monday (the link is to a full 1968 calendar). ...