Editing Advanced Composition Explorer (section)

== Instruments ==
=== Cosmic-Ray Isotope Spectrometer (CRIS) ===
[[File:ACE-cris sm.jpg|thumb|CRIS]]
The Cosmic-Ray Isotope Spectrometer covers the highest range of the Advanced Composition Explorer's energy coverage, from 50 to 500 MeV/nucleon, with an isotopic resolution for elements from Z ≈ 2 to 30. The nuclei detected in this energy interval are predominantly [[cosmic rays]] originating in our Galaxy. This sample of galactic matter investigates the nucleosynthesis of the parent material, as well as fractionation, acceleration, and transport processes that these particles undergo in the Galaxy and in the interplanetary medium. Charge and mass identification with CRIS is based on multiple measurements of dE/dx and total energy in stacks of [[Semiconductor detector|silicon detector]]s, and trajectory measurements in a scintillating optical fiber trajectory (SOFT) [[hodoscope]]. The instrument has a geometrical factor of {{cvt|250|cm2}}-sr for isotope measurements.<ref name=stone98b>{{cite journal |last=Stone |first=E. C. |title=The Cosmic-Ray Isotope Spectrometer for the Advanced Composition Explorer |journal=Space Science Reviews |date=July 1998 |volume=86 |pages=285–356 |doi=10.1023/A:1005075813033 |bibcode=1998SSRv...86..285S |display-authors=et al. |citeseerx=10.1.1.38.7241 |s2cid=12773394}}</ref>

=== Electron, Proton, and Alpha-particle Monitor (EPAM) ===
[[File:ACE-epam sm.jpg|thumb|EPAM]]
The Electron, Proton, and Alpha Monitor (EPAM) instrument on the ACE spacecraft is designed to measure a broad range of energetic particles over nearly the full unit-sphere at high time resolution. Such measurements of ions and electrons in the range of a few tens of keV to several [[Electronvolt|MeV]] are essential to understand the dynamics of [[solar flares]], co-rotating interaction regions (CIRs), interplanetary shock acceleration, and upstream terrestrial events. The large dynamic range of EPAM extends from about 50 keV to 5 MeV for ions, and 40 keV to about 350 keV for electrons. To complement its electron and ion measurements, EPAM is also equipped with a Composition Aperture (CA) which unambiguously identifies ion species reported as species group rates and/or individual pulse-height events. The instrument achieves its large spatial coverage through five telescopes oriented at various angles to the spacecraft spin axis. The low-energy particle measurements, obtained as time resolutions between 1.5 and 24 seconds, and the ability of the instrument to observe particle anisotropies in three dimensions make EPAM an excellent resource to provide the interplanetary context for studies using other instruments on the ACE spacecraft.<ref name=gold98>{{cite journal |last=Gold |first=R. E. |title=Electron, Proton, and Alpha Monitor on the Advanced Composition Explorer Spacecraft |journal=Space Science Reviews |date=July 1998 |volume=86 |pages=541–562 |doi=10.1023/A:1005088115759 |bibcode=1998SSRv...86..541G |s2cid=115540562 |display-authors=et al.}}</ref>

=== Magnetometer (MAG) ===
[[File:ACE-mag sm.jpg|thumb|MAG]]
The magnetic field experiment on ACE provides continuous measurements of the local magnetic field in the interplanetary medium. These measurements are essential in the interpretation of simultaneous ACE observations of energetic and thermal particle distributions. The experiment consists of a pair of twin, boom-mounted, triaxial [[Magnetometer|flux gate]] sensors which are located 165 inches (419&nbsp;cm) from the center of the spacecraft on opposing solar panels. The two triaxial sensors provide a balanced, fully redundant vector instrument and permit some enhanced assessment of the spacecraft's magnetic field.<ref name=smith98>{{cite journal |last=Smith |first=C. W. |title=The ACE Magnetic Fields Experiment |journal=Space Science Reviews |date=July 1998 |volume=86 |pages=613–632 |doi=10.1023/A:1005092216668 |bibcode=1998SSRv...86..613S |s2cid=189772564 |display-authors=et al.}}</ref>

=== Real-Time Solar Wind (RTSW) ===
The Real-Time Solar Wind (RTSW) system is continuously monitoring the solar wind and producing warnings of impending major geomagnetic activity, up to one hour in advance. Warnings and alerts issued by NOAA allow those with systems sensitive to such activity to take preventative action. The RTSW system gathers solar wind and energetic particle data at high time resolution from four ACE instruments (MAG, SWEPAM, EPAM, and SIS), packs the data into a low-rate bit stream, and broadcasts the data continuously. NASA sends real-time data to NOAA each day when downloading science data. With a combination of dedicated ground stations (CRL in Japan and RAL in Great Britain) and time on existing ground tracking networks (NASA DSN and the USAF's AFSCN), the RTSW system can receive data 24 hours per day throughout the year. The raw data are immediately sent from the ground station to the Space Weather Prediction Center in [[Boulder, Colorado]], processed, and then delivered to its Space Weather Operations Center where they are used in daily operations; the data are also delivered to the CRL Regional Warning Center at [[Hiraiso Station]], Japan, to the [[55th Space Weather Squadron|USAF 55th Space Weather Squadron]], and placed on the [[World Wide Web]]. The data are downloaded, processed and dispersed within 5 minutes from the time they leave ACE. The RTSW system also uses the low-energy energetic particles to warn of approaching interplanetary shocks and to help monitor the flux of high-energy particles that can produce radiation damage in satellite systems.<ref name=zwickl98>{{cite journal |last=Zwickl |first=R. D. |title=The NOAA Real-Time Solar-Wind (RTSW) System using ACE Data |journal=Space Science Reviews |date=July 1998 |volume=86 |pages=633–648 |doi=10.1023/A:1005044300738 |bibcode=1998SSRv...86..633Z |s2cid=189767518 |display-authors=et al.}}</ref>

=== Solar Energetic Particle Ionic Charge Analyzer (SEPICA) ===
[[File:ACE-sepica sm.jpg|thumb|SEPICA]]
The Solar Energetic Particle Ionic Charge Analyzer (SEPICA) was the instrument on the Advanced Composition Explorer (ACE) that determined the ionic charge states of solar and interplanetary energetic particles in the energy range from ≈0.2 MeV nucl-1 to ≈5 MeV charge-1. The charge state of energetic ions contains key information to unravel source temperatures, acceleration, fractionation, and transport processes for these particle populations. SEPICA had the ability to resolve individual charge states with a substantially larger geometric factor than its predecessor ULEZEQ on [[ISEE-1]] and [[International Cometary Explorer|ISEE-3]], on which SEPICA was based. To achieve these two requirements at the same time, SEPICA was composed of one high-charge resolution sensor section and two low-charge resolution, but large geometric factor sections.<ref name=moebius98>{{cite journal |last=Moebius |first=E. |title=The Solar Energetic Particle Ionic Charge Analyzer (SEPICA) and the Data Processing Unit (S3DPU) for SWICS, SWIMS and SEPICA |journal=Space Science Reviews |date=July 1998 |volume=86 |pages=449–495 |doi=10.1023/A:1005084014850 |bibcode=1998SSRv...86..449M |s2cid=12879423 |display-authors=et al.}}</ref>

As of 2008, this instrument is no longer functioning due to failed gas valves.<ref name="ACE Home Page"/>

=== Solar Isotope Spectrometer (SIS) ===
[[File:ACE-sis sm.jpg|thumb|SIS]]
The Solar Isotope Spectrometer (SIS) provides high-resolution measurements of the isotopic composition of energetic nuclei from He to Zn (Z=2 to 30) over the energy range from ~10 to ~100 MeV/nucleon. During large solar events, SIS measures the isotopic abundances of solar energetic particles to determine directly the composition of the [[solar corona]] and to study particle acceleration processes. During solar quiet times, SIS measures the isotopes of low-energy cosmic rays from the Galaxy and isotopes of the anomalous [[cosmic ray]] component, which originates in the nearby interstellar medium. SIS has two telescopes composed of silicon solid-state detectors that provide measurements of the nuclear charge, mass, and kinetic energy of incident nuclei. Within each telescope, particle trajectories are measured with a pair of two-dimensional silicon strip detectors instrumented with custom very-large-scale integrated (VLSI) electronics to provide both position and energy-loss measurements. SIS was specially designed to achieve excellent mass resolution under the extreme, high flux conditions encountered in large solar particle events. It provides a geometry factor of 40&nbsp;cm<sup>2</sup> sr, significantly greater than earlier solar particle isotope spectrometers.<ref name=stone98c>{{cite journal |last=Stone |first=E. C. |title=The Solar Isotope Spectrometer for the Advanced Composition Explorer |journal=Space Science Reviews |date=July 1998 |volume=86 |pages=357–408 |doi=10.1023/A:1005027929871 |bibcode=1998SSRv...86..357S |s2cid=16609619 |display-authors=et al.}}</ref>

=== Solar Wind Electron, Proton and Alpha Monitor (SWEPAM) ===
[[File:ACE-swepam sm.jpg|thumb|SWEPAM]]
The Solar Wind Electron Proton Alpha Monitor (SWEPAM) experiment provides the bulk solar wind observations for the Advanced Composition Explorer (ACE). These observations provide the context for elemental and isotopic composition measurements made on ACE as well as allowing the direct examination of numerous solar wind phenomena such as [[coronal mass ejection]], interplanetary shocks, and solar wind fine structure, with advanced, 3-D plasma instrumentation. They also provide an ideal data set for both heliospheric and [[magnetospheric]] multi-spacecraft studies where they can be used in conjunction with other, simultaneous observations from spacecraft such as [[Ulysses (spacecraft)|Ulysses]]. The SWEPAM observations are made simultaneously with independent electron (SWEPAM-e) and ion (SWEPAM-i) instruments. In order to save costs for the ACE project, SWEPAM-e and SWEPAM-i are the recycled flight spares from the joint [[NASA]]/[[European Space Agency|ESA]] Ulysses mission. Both instruments had selective refurbishment, modification, and modernization required to meet the ACE mission and spacecraft requirements. Both incorporate electrostatic analyzers whose fan-shaped fields of view sweep out all pertinent look directions as the spacecraft spins.<ref name=mccomas98>{{cite journal |last=McComas |first=D. J. |title=Solar Wind Electron Proton Alpha Monitor (SWEPAM) for the Advanced Composition Explorer |journal=Space Science Reviews |date=July 1998 |volume=86 |pages=563–612 |doi=10.1023/A:1005040232597 |bibcode=1998SSRv...86..563M |s2cid=189791714 |display-authors=et al.}}</ref>

=== Solar Wind Ion Composition Spectrometer (SWICS) and Solar Wind Ion Mass Spectrometer (SWIMS) ===
[[File:ACE-swics sm.jpg|thumb|SWICS]]
[[File:ACE-swims sm.jpg|thumb|SWIMS]]
The Solar Wind Ion Composition Spectrometer (SWICS) and the Solar Wind Ions Mass Spectrometer (SWIMS) on ACE are instruments optimized for measurements of the chemical and isotopic composition of solar and interstellar matter. SWICS determined uniquely the chemical and ionic-charge composition of the [[solar wind]], the thermal and mean speeds of all major solar wind ions from H through Fe at all solar wind speeds above 300&nbsp;km/s<sup>−1</sup> (protons) and 170&nbsp;km/s<sup>−1</sup> (Fe+16), and resolved H and He isotopes of both solar and interstellar sources. SWICS also measured the distribution functions of both the interstellar cloud and dust cloud [[pickup ion]]s up to energies of 100 keV/e<sup>−1</sup>. SWIMS measures the chemical, isotopic and charge state composition of the solar wind for every element between He and Ni. Each of the two instruments are time-of-flight [[mass spectrometer]]s and use electrostatic analysis followed by the time-of-flight and, as required, an energy measurement.<ref name=gloeckler98>{{cite journal |last=Gloeckler |first=G. |title=Investigation of the composition of solar and interstellar matter using solar wind and pickup ion measurements with SWICS and SWIMS on the ACE spacecraft |journal=Space Science Reviews |date=July 1998 |volume=86 |pages=497–539 |doi=10.1023/A:1005036131689 |bibcode=1998SSRv...86..497G |s2cid=189787814|display-authors=et al.}}</ref><ref>{{cite web |url=http://solar-heliospheric.engin.umich.edu/ace/ |title=ACE/SWICS and ACE/SWIMS |publisher=The Solar and Heliospheric Research Group |access-date=June 30, 2006 |archive-url=https://web.archive.org/web/20060810115838/http://solar-heliospheric.engin.umich.edu/ace/ |archive-date=August 10, 2006 |url-status=live}}</ref>

On 23 August 2011, the SWICS time-of-flight electronics experienced an age- and radiation-induced hardware anomaly that increased the level of background in the composition data. To mitigate the effects of this background, the model for identifying ions in the data was adjusted to take advantage of only the ion energy-per-charge as measured by the electrostatic analyzer, and the ion energy as measured by solid-state detectors. This has allowed SWICS to continue to deliver a subset of the data products that were provided to the public prior to the hardware anomaly, including ion charge state ratios of oxygen and carbon, and measurements of solar wind iron. The measurements of proton density, speed, and thermal speed by SWICS were not affected by this anomaly and continue to the present day.<ref name="ACE Home Page"/>

=== Ultra-Low-Energy Isotope Spectrometer (ULEIS) ===
[[File:ACE-uleis sm.jpg|thumb|ULEIS]]
The Ultra-Low-Energy Isotope Spectrometer (ULEIS) on the ACE spacecraft is an ultra-high-resolution [[mass spectrometer]] that measures particle composition and energy spectra of elements He–Ni with energies from ~45 keV/nucleon to a few MeV/nucleon. ULEIS investigates particles accelerated in [[solar energetic particle]] events, interplanetary shocks, and at the solar wind termination shock. By determining energy spectra, mass composition, and temporal variations in conjunction with other ACE instruments, ULEIS greatly improves our knowledge of solar abundances, as well as other reservoirs such as the local [[interstellar medium]]. ULEIS combines the high sensitivity required to measure low particle fluxes, along with the capability to operate in the largest solar particle or interplanetary shock events. In addition to detailed information for individual ions, ULEIS features a wide range of count rates for different ions and energies that allows accurate determination of particle fluxes and anisotropies over short (few minutes) time scales.<ref name=mason98>{{cite journal |last=Mason |first=G. M. |title=The Ultra-Low-Energy Isotope Spectrometer (ULEIS) for the Advanced Composition Explorer |journal=Space Science Reviews |date=July 1998 |volume=86 |pages=409–448 |doi=10.1023/A:1005079930780 |bibcode=1998SSRv...86..409M |s2cid=42297254 |display-authors=et al.}}</ref>