Advanced Composition Explorer
Encyclopedia
Advanced Composition Explorer (ACE) is a NASA
space exploration
mission being conducted as part of the Explorer program
to study matter
in situ
, comprising energetic particles from the solar wind
, the interplanetary medium
, and other sources. Real-time data from ACE is used by the Space Weather Prediction Center to improve forecasts and warnings of solar storms. The ACE robotic spacecraft
was launched August 25, 1997 and is currently operating in a Lissajous orbit
close to the L1 Lagrange point (which lies between the Sun and the Earth at a distance of some 1.5 million km from the latter). The spacecraft is still in generally good condition, and has enough fuel to maintain its orbit until 2024. NASA Goddard Space Flight Center
managed the development and integration of the ACE spacecraft.
composition of galactic cosmic ray
s. It is designed to be sensitive enough to detect isotopes up to the range of zinc
(Z-30).
ACE Real Time Solar Wind (RTSW):
Solar Wind Ion Mass Spectrometer (SWIMS) and Solar Wind Ion Composition Spectrometer (SWICS): These two instruments are time-of-flight mass spectrometers, each tuned for a different set of measurements. They analyze the chemical and isotopic composition of solar wind
and interstellar matter.
Ultra-Low Energy Isotope Spectrometer (ULEIS): ULEIS measures ion flux
and is sensitive to a range from helium
through nickel
to determine the makeup of solar energetic particles and the mechanism by which the particles become charged by the sun.
Solar Energetic Particle Ionic Charge Analyzer (SEPICA): As of 2008, this instrument is no longer functioning due to failed gas valves.
Solar Isotope Spectrometer (SIS):
Solar Wind Electron, Proton and Alpha Monitor (SWEPAM):
Electron, Proton, and Alpha-particle Monitor (EPAM):
Magnetometer (MAG):
NASA
The National Aeronautics and Space Administration is the agency of the United States government that is responsible for the nation's civilian space program and for aeronautics and aerospace research...
space exploration
Space exploration
Space exploration is the use of space technology to explore outer space. Physical exploration of space is conducted both by human spaceflights and by robotic spacecraft....
mission being conducted as part of the Explorer program
Explorer program
The Explorer program is a United States space exploration program that provides flight opportunities for physics, heliophysics, and astrophysics investigations from space. Over 90 space missions have been launched from 1958 to 2011, and it is still active...
to study matter
Matter
Matter is a general term for the substance of which all physical objects consist. Typically, matter includes atoms and other particles which have mass. A common way of defining matter is as anything that has mass and occupies volume...
in situ
In situ
In situ is a Latin phrase which translated literally as 'In position'. It is used in many different contexts.-Aerospace:In the aerospace industry, equipment on board aircraft must be tested in situ, or in place, to confirm everything functions properly as a system. Individually, each piece may...
, comprising energetic particles from the solar wind
Solar wind
The solar wind is a stream of charged particles ejected from the upper atmosphere of the Sun. It mostly consists of electrons and protons with energies usually between 1.5 and 10 keV. The stream of particles varies in temperature and speed over time...
, the interplanetary medium
Interplanetary medium
The interplanetary medium is the material which fills the solar system and through which all the larger solar system bodies such as planets, asteroids and comets move.-Composition and physical characteristics:...
, and other sources. Real-time data from ACE is used by the Space Weather Prediction Center to improve forecasts and warnings of solar storms. The ACE robotic spacecraft
Robotic spacecraft
A robotic spacecraft is a spacecraft with no humans on board, that is usually under telerobotic control. A robotic spacecraft designed to make scientific research measurements is often called a space probe. Many space missions are more suited to telerobotic rather than crewed operation, due to...
was launched August 25, 1997 and is currently operating in a Lissajous orbit
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 around a libration point are curved paths that lie...
close to the L1 Lagrange point (which lies between the Sun and the Earth at a distance of some 1.5 million km from the latter). The spacecraft is still in generally good condition, and has enough fuel to maintain its orbit until 2024. NASA Goddard Space Flight Center
Goddard Space Flight Center
The Goddard Space Flight Center is a major NASA space research laboratory established on May 1, 1959 as NASA's first space flight center. GSFC employs approximately 10,000 civil servants and contractors, and is located approximately northeast of Washington, D.C. in Greenbelt, Maryland, USA. GSFC,...
managed the development and integration of the ACE spacecraft.
Instrumentation
Cosmic Ray Isotope Spectrometer (CRIS): CRIS determines the isotopeIsotope
Isotopes are variants of atoms of a particular chemical element, which have differing numbers of neutrons. Atoms of a particular element by definition must contain the same number of protons but may have a distinct number of neutrons which differs from atom to atom, without changing the designation...
composition of galactic cosmic ray
Galactic cosmic ray
Galactic cosmic rays are cosmic rays that have their origin inside our Galaxy. GCRs are high-energy charged particles, and are usually protons, electrons, and fully ionized nuclei of light elements...
s. It is designed to be sensitive enough to detect isotopes up to the range of zinc
Zinc
Zinc , or spelter , is a metallic chemical element; it has the symbol Zn and atomic number 30. It is the first element in group 12 of the periodic table. Zinc is, in some respects, chemically similar to magnesium, because its ion is of similar size and its only common oxidation state is +2...
(Z-30).
ACE Real Time Solar Wind (RTSW):
Solar Wind Ion Mass Spectrometer (SWIMS) and Solar Wind Ion Composition Spectrometer (SWICS): These two instruments are time-of-flight mass spectrometers, each tuned for a different set of measurements. They analyze the chemical and isotopic composition of solar wind
Solar wind
The solar wind is a stream of charged particles ejected from the upper atmosphere of the Sun. It mostly consists of electrons and protons with energies usually between 1.5 and 10 keV. The stream of particles varies in temperature and speed over time...
and interstellar matter.
Ultra-Low Energy Isotope Spectrometer (ULEIS): ULEIS measures ion flux
Flux
In the various subfields of physics, there exist two common usages of the term flux, both with rigorous mathematical frameworks.* In the study of transport phenomena , flux is defined as flow per unit area, where flow is the movement of some quantity per time...
and is sensitive to a range from helium
Helium
Helium is the chemical element with atomic number 2 and an atomic weight of 4.002602, which is represented by the symbol He. It is a colorless, odorless, tasteless, non-toxic, inert, monatomic gas that heads the noble gas group in the periodic table...
through nickel
Nickel
Nickel is a chemical element with the chemical symbol Ni and atomic number 28. It is a silvery-white lustrous metal with a slight golden tinge. Nickel belongs to the transition metals and is hard and ductile...
to determine the makeup of solar energetic particles and the mechanism by which the particles become charged by the sun.
Solar Energetic Particle Ionic Charge Analyzer (SEPICA): As of 2008, this instrument is no longer functioning due to failed gas valves.
Solar Isotope Spectrometer (SIS):
Solar Wind Electron, Proton and Alpha Monitor (SWEPAM):
Electron, Proton, and Alpha-particle Monitor (EPAM):
Magnetometer (MAG):