Pioneer P-31
Encyclopedia
Pioneer P-31 was intended to be a lunar orbiter probe, but the mission failed shortly after launch. The objectives were to place a highly instrumented probe in lunar orbit, to investigate the environment between the Earth
and Moon
, and to develop technology for controlling and maneuvering spacecraft from Earth. It was equipped to take images of the lunar surface with a television-like system, estimate the Moon's mass and topography
of the poles, record the distribution and velocity of micrometeorites, and study radiation
, magnetic field
s, and low frequency electromagnetic waves in space. A midcourse propulsion system and injection rocket would have been the first United States
self-contained propulsion system capable of operation many months after launch at great distances from Earth and the first U.S. tests of maneuvering a satellite in space.
coupled to Thor-Able upper stages including an Able solid propellant third stage. The vehicle exploded at T+68 seconds after launch at an altitude of 12 km. The payload fell into the Atlantic Ocean
12 to 20 km from Cape Canaveral
in about 20 meter deep water. Subsequent investigation revealed that the second stage had ignited during ascent, detonating the Atlas's fuel supply.
satellite which failed, a 1 meter diameter sphere with a propulsion system mounted on the bottom giving a total length of 1.4 meters. The mass of the structure and aluminum alloy shell was about 30 kg and the propulsion units roughly 90 kg. Four solar panels, each 60 x 60 cm and containing 2200 solar cells in 22 100-cell nodules, extended from the sides of the spherical shell in a "paddle-wheel" configuration with a total span of about 2.7 meters. The solar panels charged nickel-cadmium batteries
. Inside the shell, a large spherical hydrazine tank made up most of the volume, topped by two smaller spherical nitrogen tanks and a 90 N injection rocket to slow the spacecraft down to go into lunar orbit, which was designed to be capable of firing twice during the mission. Attached to the bottom of the sphere was a 90 N vernier rocket for mid-course propulsion and lunar orbit maneuvers which could be fired four times.
Around the upper hemisphere of the hydrazine tank was a ring-shaped instrument platform which held the batteries in two packs, two 1.5 W UHF transmitters and diplexers, logic modules for scientific instruments, two command receivers, decoders, a buffer/amplifier, three converters, a telebit, a command box, and most of the scientific instruments. Two dipole UHF antennas protruded from the top of the sphere on either side of the injection rocket nozzle. Two dipole UHF antennas and a long VLF antenna protruded from the bottom of the sphere. The transmitters operated on a frequency of 378 megahertz.
Thermal control was planned to be achieved by fifty small "propeller blade" devices on the surface of the sphere. The blades themselves were made of reflective material and consist of four vanes which were flush against the surface, covering a black heat-absorbing pattern painted on the sphere. A thermally sensitive coil was attached to the blades in such a way that low temperatures within the satellite would cause the coil to contract and rotate the blades and expose the heat absorbing surface, and high temperatures would cause the blades to cover the black patterns. Square heat-sink units were also mounted on the surface of the sphere to help dissipate heat from the interior.
to measure total radiation flux
, a proportional radiation counter telescope to measure high energy radiation, a scintillation counter to monitor low-energy radiation, a scintillation spectrometer to study the Earth's (and possible lunar) radiation belts, a VLF receiver for natural radio wave
s, a transponder to study electron density, and part of the flux-gate and search coil magnetometers mounted on the instrument platform. A plasma probe was mounted on the sphere to measure energy and momentum distribution of protons above a few kilovolts to study the radiation effect of solar flares. The micrometeorite detector and sun scanner were mounted on the sphere as well. The only difference between Pioneer P-31 and the earlier Pioneer P-30 was the addition of a solid state detector sensitive to low energy protons on the satellite and an STL-designed rubidium frequency standard experiment placed on a pod attached to the booster. The total mass of the science package including electronics and power supply was roughly 60 kg. Total cost of the mission was estimated at 9 - 10 million dollars.
Earth
Earth is the third planet from the Sun, and the densest and fifth-largest of the eight planets in the Solar System. It is also the largest of the Solar System's four terrestrial planets...
and 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...
, and to develop technology for controlling and maneuvering spacecraft from Earth. It was equipped to take images of the lunar surface with a television-like system, estimate the Moon's mass and topography
Topography
Topography is the study of Earth's surface shape and features or those ofplanets, moons, and asteroids...
of the poles, record the distribution and velocity of micrometeorites, and study radiation
Radiation
In physics, radiation is a process in which energetic particles or energetic waves travel through a medium or space. There are two distinct types of radiation; ionizing and non-ionizing...
, magnetic field
Magnetic field
A magnetic field is a mathematical description of the magnetic influence of electric currents and magnetic materials. The magnetic field at any given point is specified by both a direction and a magnitude ; as such it is a vector field.Technically, a magnetic field is a pseudo vector;...
s, and low frequency electromagnetic waves in space. A midcourse propulsion system and injection rocket would have been the first United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
self-contained propulsion system capable of operation many months after launch at great distances from Earth and the first U.S. tests of maneuvering a satellite in space.
Mission
The spacecraft was launched on an Air Force-Convair Atlas D intercontinental ballistic missileBallistic missile
A ballistic missile is a missile that follows a sub-orbital ballistic flightpath with the objective of delivering one or more warheads to a predetermined target. The missile is only guided during the relatively brief initial powered phase of flight and its course is subsequently governed by the...
coupled to Thor-Able upper stages including an Able solid propellant third stage. The vehicle exploded at T+68 seconds after launch at an altitude of 12 km. The payload fell into the Atlantic Ocean
Atlantic Ocean
The Atlantic Ocean is the second-largest of the world's oceanic divisions. With a total area of about , it covers approximately 20% of the Earth's surface and about 26% of its water surface area...
12 to 20 km from Cape Canaveral
Cape Canaveral
Cape Canaveral, from the Spanish Cabo Cañaveral, is a headland in Brevard County, Florida, United States, near the center of the state's Atlantic coast. Known as Cape Kennedy from 1963 to 1973, it lies east of Merritt Island, separated from it by the Banana River.It is part of a region known as the...
in about 20 meter deep water. Subsequent investigation revealed that the second stage had ignited during ascent, detonating the Atlas's fuel supply.
Spacecraft design
Pioneer P-31 was virtually identical to the earlier Pioneer P-30Pioneer P-30
Pioneer P-30 was intended to be a lunar orbiter probe, but the mission failed shortly after launch on September 25, 1960. The objectives were to place a highly instrumented probe in lunar orbit, to investigate the environment between the Earth and Moon, and to develop technology for controlling...
satellite which failed, a 1 meter diameter sphere with a propulsion system mounted on the bottom giving a total length of 1.4 meters. The mass of the structure and aluminum alloy shell was about 30 kg and the propulsion units roughly 90 kg. Four solar panels, each 60 x 60 cm and containing 2200 solar cells in 22 100-cell nodules, extended from the sides of the spherical shell in a "paddle-wheel" configuration with a total span of about 2.7 meters. The solar panels charged nickel-cadmium batteries
Nickel-cadmium battery
The nickel–cadmium battery ' is a type of rechargeable battery using nickel oxide hydroxide and metallic cadmium as electrodes....
. Inside the shell, a large spherical hydrazine tank made up most of the volume, topped by two smaller spherical nitrogen tanks and a 90 N injection rocket to slow the spacecraft down to go into lunar orbit, which was designed to be capable of firing twice during the mission. Attached to the bottom of the sphere was a 90 N vernier rocket for mid-course propulsion and lunar orbit maneuvers which could be fired four times.
Around the upper hemisphere of the hydrazine tank was a ring-shaped instrument platform which held the batteries in two packs, two 1.5 W UHF transmitters and diplexers, logic modules for scientific instruments, two command receivers, decoders, a buffer/amplifier, three converters, a telebit, a command box, and most of the scientific instruments. Two dipole UHF antennas protruded from the top of the sphere on either side of the injection rocket nozzle. Two dipole UHF antennas and a long VLF antenna protruded from the bottom of the sphere. The transmitters operated on a frequency of 378 megahertz.
Thermal control was planned to be achieved by fifty small "propeller blade" devices on the surface of the sphere. The blades themselves were made of reflective material and consist of four vanes which were flush against the surface, covering a black heat-absorbing pattern painted on the sphere. A thermally sensitive coil was attached to the blades in such a way that low temperatures within the satellite would cause the coil to contract and rotate the blades and expose the heat absorbing surface, and high temperatures would cause the blades to cover the black patterns. Square heat-sink units were also mounted on the surface of the sphere to help dissipate heat from the interior.
On-board equipment
The scientific instruments consisted of an ion chamber and Geiger-Müller tubeGeiger-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...
to measure total radiation flux
Radiation flux
Radiation flux is a measure of the flow of radiation from a given radioactive source.Radiation flux density is a related measure that adds area dimensions to the above definition - for example, radiation-flux/square-centimeter....
, a proportional radiation counter telescope to measure high energy radiation, a scintillation counter to monitor low-energy radiation, a scintillation spectrometer to study the Earth's (and possible lunar) radiation belts, a VLF receiver for natural radio wave
Radio Wave
Radio Wave may refer to:*Radio frequency*Radio Wave 96.5, a radio station in Blackpool, UK...
s, a transponder to study electron density, and part of the flux-gate and search coil magnetometers mounted on the instrument platform. A plasma probe was mounted on the sphere to measure energy and momentum distribution of protons above a few kilovolts to study the radiation effect of solar flares. The micrometeorite detector and sun scanner were mounted on the sphere as well. The only difference between Pioneer P-31 and the earlier Pioneer P-30 was the addition of a solid state detector sensitive to low energy protons on the satellite and an STL-designed rubidium frequency standard experiment placed on a pod attached to the booster. The total mass of the science package including electronics and power supply was roughly 60 kg. Total cost of the mission was estimated at 9 - 10 million dollars.