Spacecraft Magnetometer
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Spacecraft magnetometers are
magnetometer A magnetometer is a device that measures magnetic field or magnetic dipole moment. Different types of magnetometers measure the direction, strength, or relative change of a magnetic field at a particular location. A compass is one such device, ...
s used aboard
spacecraft A spacecraft is a vehicle that is designed spaceflight, to fly and operate in outer space. Spacecraft are used for a variety of purposes, including Telecommunications, communications, Earth observation satellite, Earth observation, Weather s ...
and
satellites A satellite or an artificial satellite is an object, typically a spacecraft, placed into orbit around a celestial body. They have a variety of uses, including communication relay, weather forecasting, navigation ( GPS), broadcasting, scientif ...
, mostly for scientific investigations, plus attitude sensing. Magnetometers are among the most widely used
scientific instrument A scientific instrument is a device or tool used for scientific purposes, including the study of both natural phenomena and theoretical research. History Historically, the definition of a scientific instrument has varied, based on usage, laws, an ...
s in exploratory and observation satellites. These instruments were instrumental in mapping the
Van Allen radiation belt The Van Allen radiation belt is a zone of energetic charged particles, most of which originate from the solar wind, that are captured by and held around a planet by that planet's magnetosphere. Earth has two such belts, and sometimes others ma ...
s around Earth after its discovery by
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 ...
, and have detailed the
magnetic fields A magnetic field (sometimes called B-field) is a physical 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 ...
of the
Earth Earth is the third planet from the Sun and the only astronomical object known to Planetary habitability, harbor life. This is enabled by Earth being an ocean world, the only one in the Solar System sustaining liquid surface water. Almost all ...
,
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 ...
,
Sun The Sun is the star at the centre of the Solar System. It is a massive, nearly perfect sphere of hot plasma, heated to incandescence by nuclear fusion reactions in its core, radiating the energy from its surface mainly as visible light a ...
,
Mars Mars is the fourth planet from the Sun. It is also known as the "Red Planet", because of its orange-red appearance. Mars is a desert-like rocky planet with a tenuous carbon dioxide () atmosphere. At the average surface level the atmosph ...
,
Venus Venus is the second planet from the Sun. It is often called Earth's "twin" or "sister" planet for having almost the same size and mass, and the closest orbit to Earth's. While both are rocky planets, Venus has an atmosphere much thicker ...
and other planets and moons. There are ongoing missions using magnetometers, including attempts to define the shape and activity of
Saturn Saturn is the sixth planet from the Sun and the second largest in the Solar System, after Jupiter. It is a gas giant, with an average radius of about 9 times that of Earth. It has an eighth the average density of Earth, but is over 95 tim ...
's core. The first spacecraft-borne magnetometer was placed on the
Sputnik 3 Sputnik 3 (, Satellite 3) was a Soviet satellite launched on 15 May 1958 from Baikonur Cosmodrome by a modified R-7/SS-6 ICBM. The scientific satellite carried a large array of instruments for geophysical research of the upper atmosphere and n ...
spacecraft in 1958 and the most detailed magnetic observations of the Earth have been performed by the Magsat and Ă˜rsted satellites. Magnetometers were taken to the Moon during the later
Apollo Apollo is one of the Twelve Olympians, Olympian deities in Ancient Greek religion, ancient Greek and Ancient Roman religion, Roman religion and Greek mythology, Greek and Roman mythology. Apollo has been recognized as a god of archery, mu ...
missions. Many instruments have been used to measure the strength and direction of
magnetic field line A magnetic field (sometimes called B-field) is a physical 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 ...
s around Earth and the
Solar System The Solar SystemCapitalization of the name varies. The International Astronomical Union, the authoritative body regarding astronomical nomenclature, specifies capitalizing the names of all individual astronomical objects but uses mixed "Sola ...
. Spacecraft magnetometers basically fall into three categories: fluxgate, search-coil and
ionized Ionization or ionisation is the process by which an atom or a molecule acquires a negative or positive charge by gaining or losing electrons, often in conjunction with other chemical changes. The resulting electrically charged atom or molecule i ...
gas magnetometers. The most accurate magnetometer complexes on spacecraft contain two separate instruments, with a
helium Helium (from ) is a chemical element; it has chemical symbol, symbol He and atomic number 2. It is a colorless, odorless, non-toxic, inert gas, inert, monatomic gas and the first in the noble gas group in the periodic table. Its boiling point is ...
ionized gas magnetometer used to calibrate the fluxgate instrument for more accurate readings. Many later magnetometers contain small ring-coils oriented at 90° in two dimensions relative to each other forming a triaxial framework for indicating direction of magnetic field.


Magnetometer types

Magnetometers for non-space use evolved from the 19th to mid-20th centuries, and were first employed in spaceflight by Sputnik 3 in 1958. A main constraint on magnetometers in space is the availability of power and mass. Magnetometers fall into 3 major categories: the fluxgate type, search coil and the ionized vapor magnetometers. The newest type is the Overhauser type based on
nuclear magnetic resonance Nuclear magnetic resonance (NMR) is a physical phenomenon in which nuclei in a strong constant magnetic field are disturbed by a weak oscillating magnetic field (in the near field) and respond by producing an electromagnetic signal with a ...
technology.


Fluxgate magnetometers

Fluxgate magnetometers are used for their electronic simplicity and low weight. There have been several types of fluxgate used in spacecraft, which vary in two regards. Primarily better readings are obtained with three magnetometers, each pointing in a different direction. Some spacecraft have instead achieved this by rotating the craft and taking readings at 120° intervals, but this creates other issues. The other difference is in the configuration, which is simple and circular. Magnetometers of this type were equipped on the " Pioneer 0"/Able 1, " Pioneer 1"/Able 2, Ye1.1, Ye1.2, and Ye1.3 missions that failed in 1958 due to launch problems. The Pioneer 1 however did collect data on the Van Allen belts.Asif A. Siddiq
1958. Deep space chronicle. A Chronology of Deep Space and Planetary Probes 1958–2000
History. NASA.
In 1959 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 ...
"/Ye1.4 carried a three-component magnetometer that passed the Moon en route to a heliocentric orbit at a distance of , but the magnetic field could not be accurately assessed. Eventually the USSR managed a lunar impact with "
Luna 2 ''Luna 2'' (), originally named the Second Soviet Cosmic Rocket and nicknamed Lunik 2 in contemporaneous media, was the sixth of the Soviet Union's Luna programme spacecraft launched to the Moon, E-1 No.7. It was the first spacecraft Moon landi ...
", a three component magnetometer, finding no significant magnetic field in close approach to the surface. Explorer 10 had an abbreviated 52 hr mission with two fluxgate magnetometers on board. During 1958 and 1959 failure tended to characterize missions carrying magnetometers: 2 instruments were lost on Able IVB alone. In early 1966 the
USSR The Union of Soviet Socialist Republics. (USSR), commonly known as the Soviet Union, was a List of former transcontinental countries#Since 1700, transcontinental country that spanned much of Eurasia from 1922 until Dissolution of the Soviet ...
finally placed
Luna 10 Luna 10 (or Lunik 10) was a 1966 Soviet lunar robotic spacecraft mission in the Luna program. It was the first artificial satellite of the Moon, and any other body other than Earth and the Sun (in heliocentric orbit). Luna 10 conducted extens ...
in orbit around the Moon carrying a magnetometer and was able to confirm the weak nature of the Moon's magnetic field.
Venera 4 Venera 4 (), also designated 4V-1 No.310, was a probe in the Soviet Venera program for the exploration of Venus. The probe comprised a lander, designed to enter the Venusian atmosphere and parachute to the surface, and a carrier/ flyby space ...
, 5, and 6 also carried magnetometers on their trips to
Venus Venus is the second planet from the Sun. It is often called Earth's "twin" or "sister" planet for having almost the same size and mass, and the closest orbit to Earth's. While both are rocky planets, Venus has an atmosphere much thicker ...
, although they were not placed on the landing craft.


Vector sensors

The majority of early fluxgate magnetometers on spacecraft were made as vector sensors. However, the magnetometer electronics created
harmonic In physics, acoustics, and telecommunications, a harmonic is a sinusoidal wave with a frequency that is a positive integer multiple of the ''fundamental frequency'' of a periodic signal. The fundamental frequency is also called the ''1st har ...
s which interfered with readings. Properly designed sensors had feedback electronics to the detector that effectively neutralized the harmonics.
Mariner 1 Mariner 1, built to conduct the first American planetary flyby of Venus, was the first spacecraft of NASA's interplanetary Mariner program. Developed by Jet Propulsion Laboratory, and originally planned to be a purpose-built probe launched summ ...
and
Mariner 2 Mariner 2 (Mariner-Venus 1962), an American space probe to Venus, was the first robotic space probe to report successfully from a planetary encounter. The first successful spacecraft in the NASA Mariner program, it was a simplified version of t ...
carried fluxgate-vector sensor devices. Only Mariner 2 survived launch and as it passed Venus on December 14, 1962 it failed to detect a magnetic field around the planet. This was in part due to the distance of the spacecraft from the planet, noise within the magnetometer, and a very weak Venusian magnetic field. Pioneer 6, launched in 1965, is one of 4 Pioneer satellites circling the Sun and relaying information to Earth about solar winds. This spacecraft was equipped with a single vector-fluxgate magnetometer.


Ring core and spherical

Ring core sensor fluxgate magnetometers began replacing vector sensor magnetometers with the
Apollo 16 Apollo 16 (April 1627, 1972) was the tenth human spaceflight, crewed mission in the United States Apollo program, Apollo space program, administered by NASA, and the fifth and penultimate to Moon landing, land on the Moon. It was the second o ...
mission in 1972, where a three axis magnetometer was placed on the Moon. These sensors were used on a number of satellites including Magsat, Voyager, '' Ulysses'',
Giotto Giotto di Bondone (; – January 8, 1337), known mononymously as Giotto, was an List of Italian painters, Italian painter and architect from Florence during the Late Middle Ages. He worked during the International Gothic, Gothic and Italian Ren ...
, AMPTE. The
Lunar Prospector ''Lunar Prospector'' was a spacecraft that orbited the Moon for 19 months in 1998-99. From a low polar orbit, it mapped surface composition including lunar hydrogen deposits, measured magnetic and gravity fields, and studied lunar outgassing e ...
-1 uses ring-coil made of these alloys extended away from each other and its spacecraft to look for remnant magnetism in the Moons 'non-magnetic' surface. Properly configured, the magnetometers are capable of measuring magnetic field differences of 1 nT. These devices, with cores about 1 cm in size, were of lower weight than vector sensors. However, these devices were found to have non-linear output with magnetic fields greater than >5000 nT. Later it was discovered that creating a spherical structure with feedback loops wire transverse to the ring in the sphere could negate this effect. These later magnetometers were called spherical fluxgate or compact spherical core (CSC) magnetometers used in the Ă˜rsted satellite. The metal alloys that form the core of these magnetometers has also improved since Apollo-16 mission with latest using advanced molybdenum-permalloy alloys, producing lower noise with more stable output.


Search-coil magnetometer

Search-coil magnetometers, also called induction magnetometers, are wound coils around a core of high magnetic permeability. Search coils concentrate magnetic field lines inside the core along with fluctuations. The benefit of these magnetometers is that they measure alternating magnetic field and so can resolve changes in magnetic fields quickly, many times per second. Following
Lenz's law Lenz's law states that the direction of the electric current Electromagnetic induction, induced in a Electrical conductor, conductor by a changing magnetic field is such that the magnetic field created by the induced current opposes changes in t ...
, the voltage is proportional to the time derivative of magnetic flux. The voltage will be amplified by the apparent permeability of the core. This apparent permeability (μa) is defined as: \ _a= \frac \mu . The Pioneer 5 mission finally managed to get a working magnetometer of this type in orbit around the Sun showing that magnetic fields existed between Earth and Venus orbits. A single magnetometer was oriented along the plane perpendicular to the spin axis of the spacecraft. Search coil magnetometers have become increasingly more common in Earth observation satellites. A commonly used instrument is the triaxial search-coil magnetometer. Orbiting Geophysical Observatory (OGO missions - OGO-1 to OGO-6) The
Vela (satellite) Vela was the name of a group of reconnaissance satellites developed as the Vela Hotel element of Project Vela by the United States to detect nuclear detonations and monitor Soviet Union compliance with the 1963 Partial Test Ban Treaty. Vela sta ...
mission used this type as part of a package to determine if nuclear weapons evaluation was being conducted outside Earth's atmosphere. In September 1979 a Vela satellite collected evidence of a potential nuclear burst over the South Western Indian Ocean. In 1997 the US created the FAST that was designed to investigate aurora phenomena over the poles. And currently it is investigating magnetic fields at 10 to 30 Earth radii with the THEMIS satellites THEMIS, which stands for ''Time History of Events and Macroscale Interactions during Substorms'' is an array of five satellites which hope to gather more precise history of how magnetic storms arise and dissipate.


Ionized gas magnetometers


Heavy metal — scalar

Certain spacecraft, like Magsat, are equipped with scalar magnetometer. The output of these device, often in out frequency, is proportional to the magnetic field. The Magsat and Grm-A1 had cesium-vapor (cesium-133) sensor heads of dual-cell design, this design left two small dead zones. Explorer 10 (P14) was equipped with a rubidium vapor magnetometer, presumably a scalar magnetometer since the spacecraft also had a fluxgate. The magnetometer was fouled accidentally which caused it to overheat, it worked for a period of time but 52 h into the mission transmission went dead and was not regained. Ranger 1 and 2 carried a rubidium vapor magnetometer, failed to reach lunar orbit.


Helium

This type of magnetometer depends on the variation in helium absorptivity, when excited, polarized infrared light with an applied magnetic field. A low field vector-helium magnetometer was equipped on the
Mariner 4 Mariner 4 (Mariner C-3, together with Mariner 3 known as Mariner-Mars 1964) was the Mariner program, fourth in a series of spacecraft intended for planetary exploration in a flyby mode. It was designed to conduct closeup scientific observations ...
spacecraft to Mars like the Venus probe a year earlier, no magnetic field was detected.
Mariner 5 Mariner 5 (Mariner V or Mariner Venus 1967) was a spacecraft of the Mariner program that carried a complement of experiments to probe Venus' atmosphere by radio occultation, measure the hydrogen Lyman-alpha (hard ultraviolet) spectrum, and sam ...
used a similar device For this experiment a low-field helium magnetometer was used to obtain triaxial measurements of interplanetary and Venusian magnetic fields. Similar in accuracy to the triaxial flux-gated magnetometers this device produced more reliable data.


Other types

Overhauser magnetometer provides extremely accurate measurements of the strength of the
magnetic field A magnetic field (sometimes called B-field) is a physical 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 ...
. The Ă˜rsted satellite uses this type of magnetometer to map the magnetic fields over the surface of the Earth. On the Vanguard 3 mission (1959) a proton processional magnetometer was used to measure geomagnetic fields. The proton source was hexane.


Configurations of magnetometers

Unlike ground-based magnetometers that can be oriented by the user to determine the direction of magnetic field, in space the user is linked by telecommunications to a satellite traveling at 25,000 km per hour. The magnetometers used need to give an accurate reading quickly to be able to deduce magnetic fields. Several strategies can be employed, it is easier to rotate a space craft about its axis than to carry the weight of an additional magnetometer. Another strategy is to increase the size of the rocket, or make the magnetometer lighter and more effective. One of the problems, for example in studying planets with low magnetic fields like Venus, does require more sensitive equipment. The equipment has necessarily needed to evolve for today's modern task. Ironically satellites launched more the 20 years ago still have working magnetometers in places where it would take decades to reach today, at the same time the latest equipment is being used to analyze changes in the Earth here at home.


Uniaxial

These simple fluxgate magnetometers were used on many missions. On
Pioneer 6 ''Pioneer 6'', ''7'', ''8'', and ''9'' were unmanned space mission, space probes in the Pioneer program, launched between 1965 and 1969. They were a series of solar-orbiting, spin-stabilized, solar cell- and battery-powered satellites designed ...
and Injun 1 the magnetometers were mounted to a bracket external to the space craft and readings were taken as the spacecraft rotated every 120°.
Pioneer 7 Pioneer commonly refers to a person who is among the first at something that is new to a community. A pioneer as a settler is among the first settling at a place that is new to the settler community. A historic example are American pioneers, perso ...
and Pioneer 8 are configured similarly. The fluxgate on
Explorer 6 Explorer 6, or S-2, was a NASA satellite, launched on 7 August 1959, at 14:24:20 GMT. It was a small, spherical satellite designed to study trapped radiation of various energies, galactic cosmic rays, geomagnetism, radio propagation in the ...
was mounted along the spin axis to verify spacecraft tracking magnetic field lines. Search coil magnetometers were used on Pioneer 1, Explorer 6, Pioneer 5, and
Deep Space 1 ''Deep Space 1'' (DS1) was a NASA technology demonstration spacecraft which flew by an asteroid and a comet. It was part of the New Millennium Program, dedicated to testing advanced technologies. Launched on 24 October 1998, the ''Deep Space ...
.


Diaxial

A two axis magnetometer was mounted to the ATS-1 (Applications Technology Satellite). One sensor was on a 15 cm boom and the other on the spacecraft's spin axis (Spin stabilized satellite). The Sun was used to sense the position of the boom mounted device, and triaxial vector measurements could be calculated. Compared to other boom mounted magnetometers, this configuration had considerable interference. With this spacecraft, the sun induced magnetic oscillations and this allowed the continued use of the magnetometer after the
Sun sensor A Sun sensor is a navigational instrument used by spacecraft to detect the position of the Sun. Sun sensors are used for Spacecraft attitude control, attitude control, solar array pointing, gyroscope, gyro updating, and safe mode (spacecraft), fai ...
failed. Explorer 10 had two fluxgate magnetometers but is technically classified as a dual technique since it also had a rubidium vapor magnetometer.


Triaxial

The
Sputnik Sputnik 1 (, , ''Satellite 1''), sometimes referred to as simply Sputnik, was the first artificial Earth satellite. It was launched into an elliptical low Earth orbit by the Soviet Union on 4 October 1957 as part of the Soviet space progra ...
-3 had a vector fluxgate magnetometer, however because the orientation of the spacecraft could not be determined the direction vector for the magnetic field could not be determined. Three axis magnetometers were used on
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 ...
,
Luna 2 ''Luna 2'' (), originally named the Second Soviet Cosmic Rocket and nicknamed Lunik 2 in contemporaneous media, was the sixth of the Soviet Union's Luna programme spacecraft launched to the Moon, E-1 No.7. It was the first spacecraft Moon landi ...
, Pioneer Venus,
Mariner 2 Mariner 2 (Mariner-Venus 1962), an American space probe to Venus, was the first robotic space probe to report successfully from a planetary encounter. The first successful spacecraft in the NASA Mariner program, it was a simplified version of t ...
,
Venera 1 ''Venera 1'' ( meaning ''Venus 1''), also known as Venera-1VA No.2 and occasionally in the West as ''Sputnik 8'', was the first spacecraft to perform an interplanetary flight and the first to fly past Venus, as part of the Soviet Union's Venera ...
, Explorer 12, Explorer 14, and Explorer 15.
Explorer 33 Explorer 33, also known as IMP-D and AIMP-1, is 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 ...
was 'to be' the first US spacecraft to enter stable orbit around the Moon was equipped with the most advanced magnetometer, a boom-mounted triaxial fluxgate (GFSC) magnetometer of the early-vector type. It had a small range but was accurate to a resolution of 0.25 nT. However, after a rocket failure it was left in a highly elliptical orbit around Earth that orbited through the electro/magnetic tail. The Pioneer 9 and Explorer 34 used a configuration similar to Explorer 33 to survey the magnetic field within Earth's solar orbit. Explorer 35 was the first of its type to enter stable orbit around the Moon, this proved important because with the sensitive triaxial magnetometer on board, it was found the Moon effectively had no magnetic field, no radiation belt, and solar winds directly impacted the Moon.
Lunar Prospector ''Lunar Prospector'' was a spacecraft that orbited the Moon for 19 months in 1998-99. From a low polar orbit, it mapped surface composition including lunar hydrogen deposits, measured magnetic and gravity fields, and studied lunar outgassing e ...
surveyed for surface magnetism around the Moon (1998–99), using the triaxial (extended) magnetometers. With Apollo 12 improved magnetometers were placed on the Moon as part of the
Lunar Module The Apollo Lunar Module (LM ), originally designated the Lunar Excursion Module (LEM), was the lunar lander spacecraft that was flown between lunar orbit and the Moon's surface during the United States' Apollo program. It was the first crewed s ...
/
Apollo Lunar Surface Experiments Package The Apollo Lunar Surface Experiments Package (ALSEP) comprised a set of scientific instruments placed by the astronauts at the landing site of each of the five Apollo program, Apollo missions to land on the Moon following Apollo 11 (Apollos Apol ...
(ALSEP). The magnetometer continued to work several months after that return module departed. As part of the
Apollo 14 Apollo 14 (January 31February 9, 1971) was the eighth crewed mission in the United States Apollo program, the third to Moon landing, land on the Moon, and the first to land in the Geology of the Moon#Highlands, lunar highlands. It was the las ...
ALSEP, there was a portable magnetometer. The first use of the three axis ring-coil magnetometer was on the
Apollo 16 Apollo 16 (April 1627, 1972) was the tenth human spaceflight, crewed mission in the United States Apollo program, Apollo space program, administered by NASA, and the fifth and penultimate to Moon landing, land on the Moon. It was the second o ...
Moon mission. Subsequently, it was used on the Magsat. The ''
MESSENGER Messenger, Messengers, The Messenger or The Messengers may refer to: People * Courier, a person or company that delivers messages, packages, or mail * Messenger (surname) * Bicycle messenger, a bicyclist who transports packages through cities * M ...
'' mission has triaxial ring-coil magnetometer with a range of +/- 1000 mT and a sensitivity of 0.02 mT, still in progress, the mission is designed to get detailed information about Mercurian magnetosphere. The first use of spherical magnetometer in three axis configuration was on the Ă˜rsted satellite.


Dual technique

Each type of magnetometer has its own built in 'weakness'. This can result from the design of the magnetometer to the way the magnetometer interacts with the spacecraft, radiation from the Sun, resonances, etc. Using completely different design is a way to measure which readings are the result of natural magnetic fields and the sum of magnetic fields altered by spacecraft systems. In addition each type has its strengths. The fluxgate type is relatively good at providing data that finds magnetic sources. One of the first Dual technique systems was the abbreviated Explorer 10 mission which used a rubidium vapor and biaxial fluxgate magnetometers. Vector helium is better at tracking magnetic field lines and as a scalar magnetometer. ''Cassini'' spacecraft used a Dual Technique Magnetometer. One of these devices is the ring-coil vector fluxgate magnetometer (RCFGM). The other device is a vector/scalar helium magnetometer. The RCFGM is mounted 5.5 m out on an 11 m boom with the helium device at the end.
Explorer 6 Explorer 6, or S-2, was a NASA satellite, launched on 7 August 1959, at 14:24:20 GMT. It was a small, spherical satellite designed to study trapped radiation of various energies, galactic cosmic rays, geomagnetism, radio propagation in the ...
(1959) used a search coil magnetometer to measure the gross magnetic field of the Earth and vector fluxgate., however because of induced magnetism in the space craft the fluxgate sensor became saturated and did not send data. Future missions would attempt to place magnetometers further away from the space craft. Magsat Earth geological satellite was also Dual Technique. This satellite and Grm-A1 carried a scalar cesium vapor magnetometer and vector fluxgate magnetometers. The Grm-A1 satellite carrier the magnetometer on 4 meter boom. This particular spacecraft was designed to hold in a precised equi-gravitational orbit, while taking measurements. For purposes similar to Magsat, the Ă˜rsted satellite, also used a dual technique system. The Overhauser magnetometer is situated at the end of an 8 meter long boom, in order to minimize disturbances from the satellite's electrical systems. The CSC fluxgate magnetometer is located inside the body and associated with a star tracking device. One of the greater accomplishments of the two missions, the Magsat and Ă˜rsted missions happen to capture a period of great magnetic field change, with the potential of a loss of dipole, or pole reversal.NASA AND USGS MAGNETIC DATABASE "ROCKS" THE WORLD
NASA Web Feature, NASA


By mounting

The simplest magnetometer implementations are mounted directly to their vehicles. However, this places the sensor close to potential interferences such as vehicle currents and ferrous materials. For relatively insensitive work, such as "compasses" (attitude sensing) in
Low Earth orbit A low Earth orbit (LEO) is an geocentric orbit, orbit around Earth with a orbital period, period of 128 minutes or less (making at least 11.25 orbits per day) and an orbital eccentricity, eccentricity less than 0.25. Most of the artificial object ...
, this may be sufficient. The most sensitive magnetometer instruments are mounted on long booms, deployed away from the craft (e.g., the Voyagers, '' Cassini''). Many contaminant fields then decrease strongly with distance, while background fields appear unchanged. Two magnetometers may be mounted, one only partially down the boom. The vehicle body's fields will then appear different at the two distances, while background fields may or may not change significantly over such scales. Magnetometer booms for vector instruments must be rigid, to prevent additional flexing motions from appearing in the data. Some vehicles mount magnetometers on simpler, existing appendages, such as specially designed solar arrays (e.g.,
Mars Global Surveyor ''Mars Global Surveyor'' (MGS) was an American Robotic spacecraft, robotic space probe developed by NASA's Jet Propulsion Laboratory. It launched November 1996 and collected data from 1997 to 2006. MGS was a global mapping mission that examined ...
, '' Juno'',
MAVEN MAVEN is a NASA spacecraft orbiting Mars to study the loss of that planet's atmospheric gases to space, providing insight into the history of the planet's climate and water. The name is an acronym for "Mars Atmosphere and Volatile Evolution" w ...
). This saves the cost and mass of a separate boom. However, a solar array must have its cells carefully implemented and tested to avoid becoming a contaminating field.


Examples

*
FIELDS Fields may refer to: Music *Fields (band), an indie rock band formed in 2006 * Fields (progressive rock band), a progressive rock band formed in 1971 * ''Fields'' (album), an LP by Swedish-based indie rock band Junip (2010) * "Fields", a song by ...
, on Parker Solar Probe launched 2018 *
Magnetometer A magnetometer is a device that measures magnetic field or magnetic dipole moment. Different types of magnetometers measure the direction, strength, or relative change of a magnetic field at a particular location. A compass is one such device, ...
, on ''Juno'' Jupiter Orbiter, launched 2011 arrived at Jupiter 2018 * Interior Characterization of Europa using Magnetometry


See also

*
Magnetorquer A magnetorquer or magnetic torquer (also known as a torque rod) is a satellite system for Spacecraft attitude control, attitude control, detumbling, and stabilization built from electromagnetic coils. The magnetorquer creates a magnetic dipole that ...
* Magnetometer (''Juno'')


References

{{Satellite and spacecraft instruments Spacecraft components