The Interstellar Mapping and Acceleration Probe (IMAP) is a
heliophysics mission that will simultaneously investigate two important and coupled science topics in the
heliosphere: the acceleration of energetic particles and interaction of the
solar wind with the local
interstellar medium
In astronomy, the interstellar medium is the matter and radiation that exist in the space between the star systems in a galaxy. This matter includes gas in ionic, atomic, and molecular form, as well as dust and cosmic rays. It fills interstella ...
. These science topics are coupled because particles accelerated in the inner heliosphere play crucial roles in the outer heliospheric interaction. In 2018,
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 ...
selected a team led by
David J. McComas of
Princeton University
Princeton University is a private university, private research university in Princeton, New Jersey. Founded in 1746 in Elizabeth, New Jersey, Elizabeth as the College of New Jersey, Princeton is the List of Colonial Colleges, fourth-oldest ins ...
to implement the mission, which is currently planned to launch in February 2025.
[ ][ ] IMAP will be a
Sun-tracking spin-stabilized satellite
Spacecraft attitude control is the process of controlling the orientation of a spacecraft (vehicle/satellite) with respect to an inertial frame of reference or another entity such as the celestial sphere, certain fields, and nearby objects, et ...
in orbit about the
Sun–
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 ...
L1
Lagrange point
In celestial mechanics, the Lagrange points (; also Lagrangian points or libration points) are points of equilibrium for small-mass objects under the influence of two massive orbiting bodies. Mathematically, this involves the solution of th ...
with a science payload of ten instruments. IMAP will also continuously broadcast real-time in-situ data that can be used for
space weather prediction.
It is the fifth mission selected in the
Solar Terrestrial Probes program, after
TIMED,
Hinode,
STEREO
Stereophonic sound, or more commonly stereo, is a method of sound reproduction that recreates a multi-directional, 3-dimensional audible perspective. This is usually achieved by using two independent audio channels through a configuration ...
and
MMS MMS may refer to:
Science and technology Network communication protocols
* Multimedia Messaging Service for mobile phones
* Microsoft Media Server, a content-streaming protocol (mms://)
* Manufacturing Message Specification for real time proces ...
.
Science
Acceleration of charged particles up to high energy is ubiquitous throughout the universe, occurring at
stars,
magnetospheres,
black holes
A black hole is a region of spacetime where gravity is so strong that nothing, including light or other electromagnetic waves, has enough energy to escape it. The theory of general relativity predicts that a sufficiently compact mass can def ...
,
neutron stars
A neutron star is the collapsed core of a massive supergiant star, which had a total mass of between 10 and 25 solar masses, possibly more if the star was especially metal-rich. Except for black holes and some hypothetical objects (e.g. white ...
,
supernova remnants
A supernova remnant (SNR) is the structure resulting from the explosion of a star in a supernova. The supernova remnant is bounded by an expanding shock wave, and consists of ejected material expanding from the explosion, and the interstellar mat ...
, and other locations. The precise processes behind this acceleration are not well understood. There are intermediate
suprathermal particles which have energies between the energetic particles and the bulk thermal
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 ...
. Understanding how these particles are energized and form the seed population of the energetic particles is one of the science topics that IMAP will investigate.
The
solar wind and its associated magnetic field have blown a bubble in interstellar space called the
heliosphere. IMAP will study the
heliosphere boundary where the solar wind collides with material from the rest of the
galaxy
A galaxy is a system of stars, stellar remnants, interstellar gas, dust, dark matter, bound together by gravity. The word is derived from the Greek ' (), literally 'milky', a reference to the Milky Way galaxy that contains the Solar System. ...
. Using
Energetic Neutral Atoms
Energetic Neutral Atom (ENA) imaging, often described as "seeing with atoms", is a technology used to create global images of otherwise invisible phenomena in the magnetospheres of planets and throughout the heliosphere.
The solar wind is compo ...
(ENAs), IMAP will image this interaction region from the inner
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 "Solar S ...
. In addition, IMAP will also directly measure the
neutral particles of the interstellar medium, because they flow through the heliosphere relatively unmodified.
IMAP's science goals are based on the four science objectives specified in the IMAP Announcement of Opportunity (from the outside in):
[ ]
* Improve understanding of the composition and properties of the local interstellar medium (LISM).
* Advance understanding of the temporal and spatial evolution of the boundary region in which the solar wind and the interstellar medium interact.
* Identify and advance the understanding of processes related to the interactions of the magnetic field of the Sun and the LISM.
* Identify and advance understanding of particle injection and acceleration processes near the Sun, in the heliosphere and heliosheath.
Mission
Profile
After launch, the spacecraft will take several months to transit to about away from
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 ...
towards the
Sun at what is called the first
Lagrange point
In celestial mechanics, the Lagrange points (; also Lagrangian points or libration points) are points of equilibrium for small-mass objects under the influence of two massive orbiting bodies. Mathematically, this involves the solution of th ...
(L1). The spacecraft will then use on-board propulsion to insert into an approximately 10° x 5° Lissajous orbit around L1, very similar to the orbit of
Advanced Composition Explorer (ACE). The baseline mission is 3 years, but all expendables are designed for a lifetime of more than 5 years.
Spacecraft
IMAP is a simple spin-stabilized (~4
RPM
Revolutions per minute (abbreviated rpm, RPM, rev/min, r/min, or with the notation min−1) is a unit of rotational speed or rotational frequency for rotating machines.
Standards
ISO 80000-3:2019 defines a unit of rotation as the dimensionl ...
) spacecraft with ten instruments. Daily attitude maneuvers will be used to keep the spin axis and top deck (with solar arrays) pointed in the direction of the incoming solar wind, which is a few degrees away from the Sun. In the L1
Lissajous orbit
In orbital mechanics, a Lissajous orbit (), named after Jules Antoine Lissajous, is a quasi-periodic orbital trajectory that an object can follow around a Lagrangian point of a three-body system without requiring any propulsion. Lyapunov orbits ...
, the rear deck, with its communication antenna, approximately points at the Earth.
[
]
Instruments
The ten instruments on IMAP can be grouped into three categories: 1) Energetic neutral atom
Energetic Neutral Atom (ENA) imaging, often described as "seeing with atoms", is a technology used to create global images of otherwise invisible phenomena in the magnetospheres of planets and throughout the heliosphere.
The solar wind is com ...
detectors (IMAP-Lo, IMAP-Hi, and IMAP-Ultra); 2) Charged particle detectors (SWAPI, SWE, CoDICE, and HIT); and 3) Other coordinated measurements (MAG, IDEX, GLOWS).
Shown here (top panel) are oxygen fluences measured at 1 AU by several instruments onboard Advanced Composition Explorer (ACE) during a 3-year period, with representative particle spectra obtained for gradual and impulsive Solar Energetic Particles
Solar energetic particles (SEP), formerly known as solar cosmic rays, are high-energy, charged particles originating in the solar atmosphere and solar wind. They consist of protons, electrons and heavy ions with energies ranging from a few tens ...
(SEPs), corotating interaction regions (CIRs), Anomalous 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 ...
(ACRs), and Galactic 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 ...
(GCRs), and (top
panel inset) ion fluxes in the Voyager 1
''Voyager 1'' is a space probe launched by NASA on September 5, 1977, as part of the Voyager program to study the outer Solar System and interstellar space beyond the Sun's heliosphere. Launched 16 days after its twin ''Voyager 2'', ''Voya ...
direction using ''in situ'' observations from Voyager and remote ENA observations from Cassini–Huygens
''Cassini–Huygens'' ( ), commonly called ''Cassini'', was a space research, space-research mission by NASA, the European Space Agency (ESA), and the Italian Space Agency (ASI) to send a space probe to study the planet Saturn and its system, i ...
and Interstellar Boundary Explorer
Interstellar Boundary Explorer (IBEX or Explorer 91 or SMEX-10) is a NASA satellite in Earth orbit that uses energetic neutral atoms (ENAs) to image the interaction region between the Solar System and interstellar space. The mission is part of ...
(IBEX). (Middle panel) SWAPI, CoDICE, and HIT provide comprehensive composition, energy, and angular distributions for all major solar wind species (core and halo), interstellar and inner source pick-up ions, suprathermal, energetic, and accelerated ions from SEPs, interplanetary shocks, as well as ACRs. SWE, CoDICE and HIT also provide energy and angular distributions of the solar wind ion and electron core, halo, strahl, as well as energetic and relativistic electrons up to 1 MeV
In physics, an electronvolt (symbol eV, also written electron-volt and electron volt) is the measure of an amount of kinetic energy gained by a single electron accelerating from rest through an Voltage, electric potential difference of one volt i ...
.[
]
IMAP-Lo
IMAP-Lo is a single-pixel neutral atom imager that gives energy and angle-resolved measurements of ISN atoms ( H, He, O, Ne, and D) tracked over >180° in ecliptic longitude and energy resolved global maps of ENA H and O. IMAP-Lo has heritage from the IBEX-Lo on IBEX but provides much larger collection power.[
]
IMAP-Hi
IMAP-Hi consists of two identical, single-pixel high energy ENA Imagers that measure H, He, and heavier ENAs from the outer heliosphere. Each IMAP-Hi Imager is very similar in design to the IBEX
An ibex (plural ibex, ibexes or ibices) is any of several species of wild goat (genus ''Capra''), distinguished by the male's large recurved horns, which are transversely ridged in front. Ibex are found in Eurasia, North Africa and East Africa. ...
-Hi ENA Imager but incorporate key modifications that enable substantially improved resolution, spectral range, and collection power. The instrument also incorporates a time-of-flight (TOF) system for identification of ENA species.[
]
IMAP-Ultra
The IMAP-Ultra instrument images the emission of ENAs produced in the heliosheath and beyond, primarily in H atoms between ~3 and 300 keV, but it is also sensitive to contributions from He and O. Ultra is nearly identical to the Jupiter Energetic Neutral Imager (JENI), in development for flight on the European Space Agency
, owners =
, headquarters = Paris, Île-de-France, France
, coordinates =
, spaceport = Guiana Space Centre
, seal = File:ESA emblem seal.png
, seal_size = 130px
, image = Views in the Main Control Room (1205 ...
's Jupiter Icy Moon Explorer (JUICE) mission to Jupiter
Jupiter is the fifth planet from the Sun and the List of Solar System objects by size, largest in the Solar System. It is a gas giant with a mass more than two and a half times that of all the other planets in the Solar System combined, but ...
and Ganymede. Ultra's primary differences from JENI are the use of two identical copies, one mounted perpendicular to the IMAP spin axis (Ultra90) and one mounted at 45° from the anti-sunward spin axis (Ultra45) for better sky coverage, and the use of slightly thicker, UV-filtering foils covering the back plane MCPs to reduce backgrounds associated with interstellar Lyman-α photons.[
]
Solar Wind and Pick-up Ion (SWAPI)
The Solar Wind and Pickup Ion (SWAPI) instrument measures solar wind H+ and He++ and interstellar He+ and H+ pick-up ions (PUIs). SWAPI is nearly identical to the ''New Horizons
''New Horizons'' is an Interplanetary spaceflight, interplanetary space probe that was launched as a part of NASA's New Frontiers program. Engineered by the Johns Hopkins University Applied Physics Laboratory (APL) and the Southwest Research ...
'' Solar Wind Around Pluto (SWAP) instrument. SWAPI is a simplification of SWAP, and by removal of SWAP's retarding potential analyzer, significantly increases transmission and improves sensitivity, further enhancing PUI observations.[
]
Solar Wind Electron (SWE)
The Solar Wind Electron (SWE) instrument measures the 3D distribution of solar wind thermal and suprathermal electrons from 1 eV to 5 keV. SWE is based on the heritage Ulysses
Ulysses is one form of the Roman name for Odysseus, a hero in ancient Greek literature.
Ulysses may also refer to:
People
* Ulysses (given name), including a list of people with this name
Places in the United States
* Ulysses, Kansas
* Ulysse ...
/ SWOOPS, ACE
An ace is a playing card, Dice, die or domino with a single Pip (counting), pip. In the standard French deck, an ace has a single suit (cards), suit symbol (a heart, diamond, spade, or club) located in the middle of the card, sometimes large a ...
/SWEPAM and Genesis
Genesis may refer to:
Bible
* Book of Genesis, the first book of the biblical scriptures of both Judaism and Christianity, describing the creation of the Earth and of mankind
* Genesis creation narrative, the first several chapters of the Book of ...
/GEM instruments, with updated electronics based on Van Allen Probes/HOPE. SWE is optimized to measure ''in situ'' solar wind electrons at L1 to provide context for the ENA measurements and perform the ''in situ'' solar wind observations necessary to understand the local structures that can affect acceleration and transport.[
]
Compact Dual Ion Composition Experiment (CoDICE)
The Compact Dual Ion Composition Experiment (CoDICE) measures charged particles in two separate energy ranges in a compact, combined instrument. CoDICELo is an electrostatic analyzer with a time-of-flight versus energy (TOF/E) subsystem to measure the 3D velocity distribution functions (VDFs) and ionic charge state and mass composition of ~0.5–80 keV/q ions. CoDICEHi uses the common TOF/E subsystem to measure the mass composition and arrival direction of ~0.03–5 MeV/nuc ions and ~20–600 keV electrons.[
]
High-energy Ion Telescope (HIT)
The High-energy Ion Telescope (HIT) uses silicon solid-state detectors to measure the elemental composition, energy spectra, angular distributions, and arrival times of H to Ni ions over a species-dependent energy range from ~2 to ~40 MeV/nuc. HIT, heavily based on the Low Energy Telescope (LET) on the Solar Terrestrial Relations Observatory (STEREO), delivers full-sky coverage with a large geometry factor. A portion of the HIT viewing area is also optimized to measure 0.5 - 1.0 MeV electrons.[
]
Magnetometer (MAG)
The IMAP magnetometer (MAG) consists of a pair of identical triaxial fluxgate magnetometers that measure the 3D interplanetary magnetic field. Both magnetometers are mounted on a 1.8 m boom, one on the end and the other in an intermediate position. This configuration, through gradiometry, reduces the effect of spacecraft magnetic fields on the measurements of the instrument by dynamically removing the spacecraft field. The MAG are based on the Magnetospheric Multiscale Mission magnetometers.[
]
Interstellar Dust Experiment (IDEX)
The Interstellar Dust Experiment (IDEX) is a high-resolution dust analyzer that provides the elemental composition, speed and mass distributions of interstellar dust
Cosmic dust, also called extraterrestrial dust, star dust or space dust, is dust which exists in outer space, or has fallen on Earth. Most cosmic dust particles measure between a few molecules and 0.1 mm (100 micrometers). Larger particles are c ...
particles. IDEX's sensor head has a large effective target area (), which allows it to collect a statistically significant number of dust impacts (> 100/year).[ This instrument was constructed at the Laboratory for Atmospheric and Space Physics (LASP) at the ]University of Colorado Boulder
The University of Colorado Boulder (CU Boulder, CU, or Colorado) is a public research university in Boulder, Colorado. Founded in 1876, five months before Colorado became a state, it is the flagship university of the University of Colorado syst ...
.
GLObal solar Wind Structure (GLOWS)
The GLObal solar Wind Structure (GLOWS) instrument measures the heliospheric resonant backscatter glow of hydrogen (the Lyman-alpha line at ) and helium (at ). GLOWS consists of two separate detectors: LαD and HeD for the two spectral channels, with the lines of sight directed at different angles with respect to the IMAP spin axis. The Lyman-α detector (LαD) is almost identical to LαD on the NASA TWINS mission, and HeD uses a new monochromator unit.[
]
Communications
Nominally, IMAP will have two 4-hour contacts per week through the NASA Deep Space Network
The NASA Deep Space Network (DSN) is a worldwide network of American spacecraft communication ground segment facilities, located in the United States (California), Spain (Madrid), and Australia (Canberra), that supports NASA's interplanetary ...
(DSN). This is sufficient to upload any commands, download the week's worth of science data and housekeeping, and perform spacecraft ranging required for navigation. DSN will communicate with the IMAP Mission Operation Center (MOC) at Johns Hopkins University
Johns Hopkins University (Johns Hopkins, Hopkins, or JHU) is a private university, private research university in Baltimore, Maryland. Founded in 1876, Johns Hopkins is the oldest research university in the United States and in the western hem ...
Applied Physics Laboratory, which will operate the spacecraft. All science and ancillary data will pass through the MOC to the Science Operations Center (SOC) at LASP
The Laboratory for Atmospheric and Space Physics (LASP) is a research organization at the University of Colorado Boulder. LASP is a research institute with over one hundred research scientists ranging in fields from solar influences, to Earth' ...
.[ The IMAP SOC at LASP will be responsible for all aspects of instrument operations: planning, commanding, health and status monitoring, anomaly response, and sustaining engineering for the instruments. The SOC will also handle science data processing (including data calibration, validation and preliminary analysis), distribution, archiving, and maintaining the IMAP data management plan. Science data will be produced centrally using algorithms, software, and calibration data provided and managed by each instrument team.
All science and other data will be shared with the heliophysics community as rapidly as practical with an open data policy compliant with the NASA Heliophysics Science Data Management Policy. The NASA Space Physics Data Facility (SPDF) is the final archive for IMAP, with regular transfer of data to the SPDF so that the data can be made available through their Coordinated Data Analysis Web (CDAWeb) site.][
]
Space weather data
IMAP will supply critical real-time space weather data through its "IMAP Active Link for Real-Time" or I-ALiRT. IMAP will continuously broadcast a small subset (500 bit/s) of the science data for I-ALiRT to supporting ground stations around the world when not in contact with the DSN. During DSN tracks, the flight system includes the space weather data in the full-rate science data stream, which the MOC receives from the DSN and forwards to the SOC. In either case, the SOC processes these real-time observations to create the data products required by the space weather community. Data include all of the important parameters currently provided by Advanced Composition Explorer (ACE), but at significantly higher cadence, and also include several new key parameters.[
]
Management
This is the fifth mission in NASA's Solar Terrestrial Probes program. The Heliophysics Program Office at NASA's 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 ...
in 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 ...
, manages the STP program for the agency's Heliophysics Science Division in Washington, D.C.
)
, image_skyline =
, image_caption = Clockwise from top left: the Washington Monument and Lincoln Memorial on the National Mall, United States Capitol, Logan Circle, Jefferson Memorial, White House, Adams Morgan, ...
The mission's principal investigator is David J. McComas of Princeton University
Princeton University is a private university, private research university in Princeton, New Jersey. Founded in 1746 in Elizabeth, New Jersey, Elizabeth as the College of New Jersey, Princeton is the List of Colonial Colleges, fourth-oldest ins ...
. The Johns Hopkins University
Johns Hopkins University (Johns Hopkins, Hopkins, or JHU) is a private university, private research university in Baltimore, Maryland. Founded in 1876, Johns Hopkins is the oldest research university in the United States and in the western hem ...
's Applied Physics Laboratory in Laurel, Maryland, will provide project management.
The mission is cost-capped at US$564 million, excluding cost for the launch on a SpaceX
Space Exploration Technologies Corp. (SpaceX) is an American spacecraft manufacturer, launcher, and a satellite communications corporation headquartered in Hawthorne, California. It was founded in 2002 by Elon Musk with the stated goal of ...
Falcon 9 launch vehicle from Cape Canaveral Space Launch Complex 40 (SLC-40) at Cape Canaveral Space Force Station
Cape Canaveral Space Force Station (CCSFS) is an installation of the United States Space Force's Space Launch Delta 45, located on Cape Canaveral in Brevard County, Florida.
Headquartered at the nearby Patrick Space Force Base, the station ...
(CCSFS) in Florida
Florida is a state located in the Southeastern region of the United States. Florida is bordered to the west by the Gulf of Mexico, to the northwest by Alabama, to the north by Georgia, to the east by the Bahamas and Atlantic Ocean, and to ...
.[ ] As of April 2020, the preliminary total cost of the mission is estimated to be US$707.7 million to US$776.3 million.
Missions of Opportunity
NASA plans on including an EELV Secondary Payload Adapter (ESPA) (Evolved expendable launch vehicle
National Security Space Launch (NSSL) — formerly Evolved Expendable Launch Vehicle (EELV) from 1994 to 2019 — is a program of the United States Space Force (USSF) intended to assure access to space for United States Department of Defense and o ...
) Grande ring below the IMAP spacecraft, which will give the opportunity for 4 or 5 secondary payloads to ride along with the IMAP launch. Deployment of the secondary payloads will occur after IMAP deployment into a transfer orbit to the Earth-Sun L1 Lagrange point
In celestial mechanics, the Lagrange points (; also Lagrangian points or libration points) are points of equilibrium for small-mass objects under the influence of two massive orbiting bodies. Mathematically, this involves the solution of th ...
. Some of the slots may be used by other divisions in the Science Mission Directorate
The Science Mission Directorate (SMD) of the National Aeronautics and Space Administration (NASA) engages the United States’ science community, sponsors scientific research, and develops and deploys satellites and probes in collaboration with NAS ...
and some may be used by other government agencies. Two opportunities for slots were competed for the Heliophysics Science Division as part of the Third Stand Alone Missions of Opportunity Notice (SALMON-3) Program Element Appendix (PEA), with proposals for both due on 30 November 2018. Selection for Phase A studies should be announced in 2019.
Science opportunity
The Announcement of Opportunity for the 2018 Heliophysics Science Missions of Opportunity (MoO) included the option of proposing a Small Complete Mission (SCM) to utilize the IMAP ESPA Grande to launch a secondary payload. Up to two ports on the ESPA Grande ring may be allocated for Science MoOs. The payloads are designated as Class D as defined in NPR 8705.4.[ ]
TechDemo opportunity
The Announcement of Opportunity for the 2018 Heliophysics Technology Demonstration (TechDemo) Missions of Opportunity requested SCM proposals for spaceflight demonstration of innovative medium Technology Readiness Level (TRL) technologies that enable significant advances in NASA's Heliophysics Science Objectives and Goals. TechDemo investigations must be proposed for flight as a secondary payload with the IMAP mission. Up to two ports on the ESPA Grande ring may be allocated for TechDemo. The payloads are designated as Class D as defined in NPR 8705.4. Down-selection is targeted for the third quarter FY 2020.[ ]
See also
* Interstellar Boundary Explorer
Interstellar Boundary Explorer (IBEX or Explorer 91 or SMEX-10) is a NASA satellite in Earth orbit that uses energetic neutral atoms (ENAs) to image the interaction region between the Solar System and interstellar space. The mission is part of ...
- The IBEX spacecraft, launched in October 2008
* Advanced Composition Explorer - The ACE spacecraft, launched in August 1997
* Voyager 1
''Voyager 1'' is a space probe launched by NASA on September 5, 1977, as part of the Voyager program to study the outer Solar System and interstellar space beyond the Sun's heliosphere. Launched 16 days after its twin ''Voyager 2'', ''Voya ...
- The Voyager 1 spacecraft, launched in September 1977
* Heliophysics Science Division - NASA science division in the Science Mission Directorate
The Science Mission Directorate (SMD) of the National Aeronautics and Space Administration (NASA) engages the United States’ science community, sponsors scientific research, and develops and deploys satellites and probes in collaboration with NAS ...
References
External links
* - Official Princeton IMAP site
ACE Home
- Official Caltech ACE site
IMAP Quick Facts
- University of Colorado, Boulder IMAP page
Heliophysics
- Official NASA Heliophysics webpage
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