Interplanetary Monitoring Platform was a program managed by the

NASA Goddard Space Flight Center The Goddard Space Flight Center (GSFC) is a major NASA space research laboratory located approximately northeast of Washington, D.C. in Greenbelt, Maryland, United States. Established on May 1, 1959 as NASA's first space flight center, GSFC empl ...

Greenbelt, Maryland Greenbelt is a city in Prince George's County, Maryland, United States, and a suburb of Washington, D.C. At the 2020 census, the population was 24,921. Greenbelt is the first and the largest of the three experimental and controversial New Deal ...

, as part of the

Explorers program The Explorers program is a NASA exploration program that provides flight opportunities for physics, geophysics, heliophysics, and astrophysics investigations from space. Launched in 1958, Explorer 1 was the first spacecraft of the United Stat ...

, with the primary objectives of investigation of interplanetary

plasma Plasma or plasm may refer to: Science * Plasma (physics), one of the four fundamental states of matter * Plasma (mineral), a green translucent silica mineral * Quark–gluon plasma, a state of matter in quantum chromodynamics Biology * Blood pla ...

and the interplanetary

magnetic field A magnetic field is a vector field that describes the magnetic influence on moving electric charges, electric currents, and magnetic materials. A moving charge in a magnetic field experiences a force perpendicular to its own velocity and to ...

. The orbiting of IMP satellites in a variety of interplanetary and

earth Earth is the third planet from the Sun and the only astronomical object known to harbor life. While large volumes of water can be found throughout the Solar System, only Earth sustains liquid surface water. About 71% of Earth's surfa ...

orbits allowed study of spatial and temporal relationships of geophysical and interplanetary phenomena simultaneously by several other

NASA The National Aeronautics and Space Administration (NASA ) is an independent agency of the US federal government responsible for the civil space program, aeronautics research, and space research. NASA was established in 1958, succeeding t ...

satellites.

Satellites

Technology

The IMP program was the first space program to use

integrated circuit An integrated circuit or monolithic integrated circuit (also referred to as an IC, a chip, or a microchip) is a set of electronic circuits on one small flat piece (or "chip") of semiconductor material, usually silicon. Large numbers of tiny ...

(IC) chips, which it first launched into space with the

IMP-A The Explorers program is a NASA exploration program that provides flight opportunities for physics, geophysics, heliophysics, and astrophysics investigations from space. Launched in 1958, Explorer 1 was the first spacecraft of the United St ...

( Explorer 18) in 1963. This predates the use of IC chips in the

Apollo Guidance Computer The Apollo Guidance Computer (AGC) was a digital computer produced for the Apollo program that was installed on board each Apollo command module (CM) and Apollo Lunar Module (LM). The AGC provided computation and electronic interfaces for guidan ...

, used for the Apollo program. The

MOSFET The metal–oxide–semiconductor field-effect transistor (MOSFET, MOS-FET, or MOS FET) is a type of field-effect transistor (FET), most commonly fabricated by the controlled oxidation of silicon. It has an insulated gate, the voltage of which d ...

(metal-oxide-semiconductor field-effect transistor, or MOS transistor) was adopted by NASA for the IMP program in 1964. The use of MOSFETs was a major step forward in

spacecraft A spacecraft is a vehicle or machine designed to fly in outer space. A type of artificial satellite, spacecraft are used for a variety of purposes, including communications, Earth observation, meteorology, navigation, space colonization, p ...

electronics The field of electronics is a branch of physics and electrical engineering that deals with the emission, behaviour and effects of electrons using electronic devices. Electronics uses active devices to control electron flow by amplification ...

design. The IMP-D (

Explorer 33 Explorer 33, also known as IMP-D and AIMP-1, was a spacecraft in the Explorer program launched by NASA on 1 July 1966 on a mission of scientific exploration. It was the fourth satellite launched as part of the Interplanetary Monitoring Platform ...

), launched in 1966, was the first spacecraft to use the MOSFET, which had been first demonstrated in 1960 and publicly revealed in 1963. MOS technology's simplicity of

semiconductor device fabrication Semiconductor device fabrication is the process used to manufacture semiconductor devices, typically integrated circuit (IC) chips such as modern computer processors, microcontrollers, and memory chips such as NAND flash and DRAM that are pres ...

and manufacturing enabled higher

transistor count The transistor count is the number of transistors in an electronic device (typically on a single substrate or "chip"). It is the most common measure of integrated circuit complexity (although the majority of transistors in modern microprocessors ...

s on

chips. This resolved a growing problem facing spacecraft designers at the time, the need for greater on-board electronic capability for

telecommunications Telecommunication is the transmission of information by various types of technologies over wire, radio, optical, or other electromagnetic systems. It has its origin in the desire of humans for communication over a distance greater than that fe ...

and other functions. The

Goddard Space Flight Center The Goddard Space Flight Center (GSFC) is a major NASA space research laboratory located approximately northeast of Washington, D.C. in Greenbelt, Maryland, United States. Established on May 1, 1959 as NASA's first space flight center, GSFC empl ...

used MOSFETs in building block circuits, with MOSFET blocks and

resistors A resistor is a passive two-terminal electrical component that implements electrical resistance as a circuit element. In electronic circuits, resistors are used to reduce current flow, adjust signal levels, to divide voltages, bias active el ...

accounting for 93% of the IMP-D's electronics. MOS technology greatly increased the number of on-board

transistors upright=1.4, gate (G), body (B), source (S) and drain (D) terminals. The gate is separated from the body by an insulating layer (pink). A transistor is a semiconductor device used to Electronic amplifier, amplify or electronic switch, switch e ...

and

communication channel A communication channel refers either to a physical transmission medium such as a wire, or to a logical connection over a multiplexed medium such as a radio channel in telecommunications and computer networking. A channel is used for informa ...

s, from 1,200 transistors and 175 channels on the first three IMP spacecraft up to 2,000 transistors and 256 channels on the IMP-D. MOS technology also greatly reduced the number of

electrical Electricity is the set of physical phenomena associated with the presence and motion of matter that has a property of electric charge. Electricity is related to magnetism, both being part of the phenomenon of electromagnetism, as described by ...

parts required on a spaceship, from 3,000 non-resistor parts on the IMP-A ( Explorer 18) down to 1,000 non-resistor parts on the IMP-D, despite the IMP-D having twice the electrical complexity of the IMP-A. The MOSFET blocks were manufactured by

General Microelectronics General Micro-electronics (GMe) was an American semiconductor company in the 1960s. It was formed by three former members of Fairchild Semiconductor, and is thus one of the "Fairchildren". It was acquired in 1966 by Philco-Ford and became their Mic ...

, which had NASA as its first MOS contract shortly after it had commercialized MOS technology in 1964.

Applications

IMPs were used to study the

magnetic fields A magnetic field is a vector field that describes the magnetic influence on moving electric charges, electric currents, and magnetic materials. A moving charge in a magnetic field experiences a force perpendicular to its own velocity and to ...

solar wind The solar wind is a stream of charged particles released from the upper atmosphere of the Sun, called the corona. This plasma mostly consists of electrons, protons and alpha particles with kinetic energy between . The composition of the sola ...

and

cosmic rays Cosmic rays are high-energy particles or clusters of particles (primarily represented by protons or atomic nuclei) that move through space at nearly the speed of light. They originate from the Sun, from outside of the Solar System in our own ...

outside the magnetic field of the Earth. It was closely related to the development of the Apollo program. The IMP program consisted of a network of eleven satellites designed to collect data on

space radiation Health threats from cosmic rays are the dangers posed by cosmic rays to astronauts on interplanetary missions or any missions that venture through the Van-Allen Belts or outside the Earth's magnetosphere. They are one of the greatest barriers ...

in support of the Apollo program. The IMP satellites investigated plasma (

ionized gas Plasma ()πλάσμα
, Henry George Liddell, R ...

), cosmic rays, and magnetic fields in interplanetary and cislunar space, from various solar and terrestrial orbits. Data gathered by IMP spacecraft and satellites were used to support the Apollo program, enabling the first manned

Moon landing A Moon landing is the arrival of a spacecraft on the surface of the Moon. This includes both crewed and robotic missions. The first human-made object to touch the Moon was the Soviet Union's Luna 2, on 13 September 1959. The United St ...

with the

Apollo 11 Apollo 11 (July 16–24, 1969) was the American spaceflight that first landed humans on the Moon. Commander Neil Armstrong and lunar module pilot Buzz Aldrin landed the Apollo Lunar Module ''Eagle'' on July 20, 1969, at 20:17 UTC, an ...

mission in 1969.

References

{{reflist

External links

IMP (Interplanetary Monitoring Platform)
David Darling Explorers Program