The spacecraft's original mission was to orbit theSun at theL1Lagrangian point, but this was delayed to study the magnetosphere and near lunar environment when theSolar and Heliospheric Observatory (SOHO) andAdvanced Composition Explorer (ACE) spacecraft were sent to the same location.Wind has been atL1 continuously since May 2004, and is still operating as of 2024[update].[2] As of 2024[update],Wind currently has enough fuel to last over 50 more years atL1, until at least 2075.[3]Wind continues to collect data, and by the end of 2024 had contributed data to over 7,850 scientific publications.[2]
The aim of theInternational Solar-Terrestrial Physics Science Initiative is to understand the behaviour of the solar-terrestrialplasma environment, in order to predict how theEarth's atmosphere will respond to changes in solar wind conditions.Wind's objective is to measure the properties of the solar wind before it reaches the Earth.
Provide complete plasma, energetic particle, and magnetic field input for magnetospheric and ionospheric studies.
Determine the magnetospheric output to interplanetary space in the up-stream region.
Investigate basic plasma processes occurring in the near-Earth solar wind.
Provide baseline ecliptic plane observations to be used in heliospheric latitudes by theUlysses mission.
TheWind spacecraft has an array of instruments including: KONUS,[4] the Magnetic Field Investigation (MFI),[5] the Solar Wind and Suprathermal Ion Composition Experiment (SMS),[6] The Energetic Particles: Acceleration, Composition, and Transport (EPACT) investigation,[7] the Solar Wind Experiment (SWE),[8] a Three-Dimensional Plasma and Energetic Particle Investigation (3DP),[9] the Transient Gamma-Ray Spectrometer (TGRS),[10] and the Radio and Plasma Wave Investigation (WAVES).[11] TheKONUS and TGRS instruments are primarily for gamma-ray and high energyphoton observations ofsolar flares orgamma-ray bursts and part of theGamma-ray Coordinates Network. The SMS experiment measures the mass and mass-to-charge ratios of heavy ions. The SWE and 3DP experiments are meant to measure/analyze the lower energy (below 10MeV) solar windprotons andelectrons. The WAVES and MFI experiments were designed to measure the electric andmagnetic fields observed in the solar wind. All together, theWind spacecraft's suite of instruments allows for a complete description of plasma phenomena in the solar wind plane of the ecliptic.
Theelectric field detectors of theWind WAVES instrument[11] are composed of three orthogonal electric fielddipole antennas, two in the spin plane (roughly the plane of theecliptic) of the spacecraft and one along the spin axis. The complete WAVES suite of instruments includes five total receivers including: Low Frequency FFT receiver called FFT (0.3 Hz to 11 kHz), Thermal Noise Receiver called TNR (4–256 kHz), Radio receiver band 1 called RAD1 (20–1040 kHz), Radio receiver band 2 called RAD2 (1.075–13.825 MHz), and the Time Domain Sampler called TDS (designed and built by theUniversity of Minnesota). The longer of the two spin planeantenna, defined as Ex, is 100 m (330 ft) tip-to-tip while the shorter, defined as Ey, is 15 m (49 ft) tip-to-tip. The spin axis dipole, defined as Ez, is roughly 12 m (39 ft) tip-to-tip. When accounting for spacecraft potential, these antenna lengths are adjusted to ~41.1 m (135 ft), ~3.79 m (12.4 ft), and ~2.17 m (7 ft 1 in) [Note: these are subject to change and only estimates and not necessarily accurate to two decimal places]. TheWind WAVES instrument also detectsmagnetic fields using three orthogonalsearch coil magnetometers (designed and built by theUniversity of Iowa). The XY search coils are oriented to be parallel to the XY dipole antenna. The search coils allow for high-frequency magnetic field measurements (defined as Bx, By, and Bz). The WAVES Z-axis is anti-parallel to the Z-GSE (Geocentric Solar Ecliptic) direction. Thus, any rotations can be done about the Z-axis in the normalEulerian sense followed by a change of sign in the Z-component of any GSE vector rotated into WAVES coordinates.
Electric (and magnetic) field waveform captures can be obtained from the Time Domain Sampler (TDS) receiver.[11] TDS samples are a waveform capture of 2048 points (16384 points on theSTEREO spacecraft) per field component. The waveforms are measures of electric field versus time. In the highest sampling rates, the Fast (TDSF) sampler runs at ~120,000 samples per second (sps) and the Slow (TDSS) sampler runs at ~7,500 sps. TDSF samples are composed of two electric field components (typically Ex and Ey) while TDSS samples are composed of four vectors, either three electric and one magnetic field or three magnetic and one electric field. The TDSF receiver has little to no gain below about ~120 Hz and the search coil magnetometers roll off around ~3.3 Hz.[12]
The TNR measures ~4–256 kHz electric fields in up to 5 logarithmically spaced frequency bands, though typically only set at 3 bands, from 32 or 16 channels per band, with a 7 nV/(Hz)1/2 sensitivity, 400 Hz to 6.4 kHz bandwidth, and total dynamic range in excess of 100dB.[11] The data are taken by two multi-channel receivers which nominally sample for 20 ms at a 1 MHz sampling rate (see Bougeret 1995[11] for more information). The TNR is often used to determine the local plasma density by observing the plasma line, an emission at the localupper hybrid frequency due to a thermal noise response of the wire dipole antenna. One should note that observation of the plasma line requires the dipole antenna to be longer than the localDebye length, λDe.[13] For typical conditions in the solar wind λDe ~7–20 m (23–66 ft), much shorter than the wire dipole antenna onWind. The majority of this section was taken from.[12]
TheWind / 3DP instrument (designed and built at the BerkeleySpace Sciences Laboratory) was designed to make full three-dimensional measurements of the distributions ofsuprathermalelectrons andions in the solar wind. The instrument includes three arrays, each consisting of a pair of double-endedsemiconductortelescopes each with two or three closely sandwiched passivated ion implantedsilicon detectors, which measure electrons and ions above ~20 keV. The instrument also has top-hat symmetrical spherical sectionelectrostatic analyzers (ES) withmicrochannel plate detectors (MCPs) are used to measure ions and electrons from ~3 eV to 30 keV.[9] The two types of detectors have energy resolutions ranging from ΔE/E ≈0.3 for the solid state telescopes (SST) and ΔE/E ≈ 0.2 for the top-hat ES analyzers. The angular resolutions are 22.5° × 36° for the SST and 5.6° (near theecliptic) to 22.5° for the top-hat ES analyzers. The particle detectors can obtain a full4π steradian coverage in one full(half) spin (~3 seconds) for the SST (top-hat ES analyzers). The majority of this section was taken from.[12]
The arrays of detectors are mounted on two opposing booms, each 0.5 m (1 ft 8 in) in length. The top-hat ES analyzers are composed of four separate detectors, each with differentgeometry factors to cover different ranges of energies. The electron detectors, EESA, and ion detectors, PESA, are each separated into low (L) and high (H) energy detectors. The H and L analyzers contain 24 and 16 discrete anodes, respectively. Theanode layout provides a 5.6° angular resolution within ± 22.5° of the ecliptic plane (increases to 22.5° at normal incidence to ecliptic plane). The analyzers are swept logarithmically in energy and counters sample at 1024 samples/spin (~3 ms sample period). Thus the analyzers can be set to sample 64 energy samples per sweep at 16 sweeps per spin or 32 energy samples per sweep at 32 sweeps per spin, etc. The detectors are defined as follows:
EESA Low (EL): covers electrons from ~3 eV to ~1 keV (These values vary from moment structure to moment structure depending on duration of data sampling, spacecraft potential, and whether in burst or survey mode. The typical range is ~5 eV to ~1.11 keV.[12]) with an 11.25° spin phase resolution. EL has a total geometric factor of 1.3 × 10−2 E cm2-sr (where E is energy in eV) with a nearly identical 180° field of view (FOV), radial to the spacecraft, to that of PESA-L.
EESA High (EH): covers electrons from ~200 eV to ~30 keV (though typical values vary from a minimum of ~137 eV to a maximum of ~28 keV) in a 32 sample energy sweep each 11.25° of spacecraft spin. EH has a total geometric factor of 2.0 × 10−1 E cm2-sr, MCP efficiency of about 70% and grid transmission of about 73%. EH has a 360° planar FOV tangent to the spacecraft surface which can be electro statically deflected into a cone up to ±45° out of its normal plane.
PESA Low (PL): covers ions with a 14 sample energy sweep (Note that in survey mode the data structures typically take 25 data points at 14 different energies while in burst mode they take 64 data points at 14 different energies.) from ~100 eV to ~10 keV (often energies range from ~700 eV to ~6 keV) each 5.6° of spacecraft spin. PL has a total geometric factor of only 1.6 × 10−4 E cm2-sr but an identical energy-angle response to that of PESA-H. While in the solar wind, PL reorients itself along the bulk flow direction to capture the solar wind flow which results in a narrow range of pitch-angle coverage.
PESA High (PH): covers ions with a 15 sample energy sweep from as low as ~80 eV to as high as ~30 keV (typical energy range is ~500 eV to ~28 keV[12]) each 11.25° of spacecraft (Note that PH has multiple data modes where the number of data points per energy bin can be any of the following: 121, 97, 88, 65, or 56). PH has a total geometric factor of 1.5 × 10−2 E cm2-sr with a MCP efficiency of about 50% and grid entrance post transmission of about 75%.
The majority of this section was taken from Wilson III (2010).[12]
The SST detectors consist of three arrays of double-ended telescopes, each of which is composed of either a pair or triplet of closely sandwichedsemiconductor detectors. The center detector (Thick or T) of the triplet is 1.5 cm2 (0.23 sq in) in area, 500 μm thick, while the other detectors, foil (F) and open (O), are the same area but only 300 μm thick. One direction of the telescopes is covered in a thinlexan foil, ~1500Angstrom (Å) ofaluminum evaporated on each side to eliminatesunlight, (SST-Foil) where the thickness was chosen to stop protons up to the energy of electrons (~400 keV). Electrons are essentially unaffected by the foil. On the opposite side (SST-Open), a commonbroom magnet is used to refuse electrons below ~400 keV from entering but leaves the ions essentially unaffected. Thus, if no higher energy particles penetrate the detector walls, the SST-Foil should only measure electrons and the SST-Open only ions. Each double-ended telescope has two 36° × 20° FWHM FOV, thus each end of the five telescopes can cover a 180° × 20° piece of space. Telescope 6 views the same angle to spin axis as telescope 2, but both ends of telescope 2 have a drilled tantalum cover to reduce the geometric factor by a factor of 10 to measure the most intense fluxes. The SST-Foil data structures typically have 7 energy bins each with 48 data points while the SST-Open has 9 energy bins each with 48 data points. Both detectors have energy resolutions of ΔE/E ≈ 30%. The majority of this section was taken from.[12]
The Magnetic Field Instrument (MFI)[5] on boardWind is composed of dual triaxialfluxgate magnetometers. The MFI has a dynamic range of ±4nT to ±65,536 nT, digital resolution ranging from ±0.001 nT to ±16 nT, sensor noise level of < 0.006 nT (R.M.S.) for 0–10 Hz signals, and sample rates varying from 44 samples per second (sps) in snapshot memory to 10.87 sps in standard mode. The data are also available in averages at 3 seconds, 1 minute, and 1 hour. The data sampled at higher rates (i.e. >10 sps) is referred to as High Time Resolution (HTR) data in some studies.[14][15]
TheWind spacecraft has twoFaraday Cup (FC) ion instruments.[8] The SWE FCs can produce reduced ion distribution functions with up to 20 angular and 30 energy per charge bins every 92 seconds.[16] Each sensor has a ~15° tilt above or below the spin plane and an energy range from ~150 eV to ~8 keV. A circular aperture limits the effects of aberration near the modulator grid and defines the collecting area of the collector plates in each FC. The FCs sample at a set energy for each spacecraft rotation, then step up the energy for the next rotation. Since there are up to 30 energy bins for these detectors, a full reduced distribution function requires 30 rotations or slightly more than 90 seconds.
KONUS remains a very active partner in theGamma-ray Coordinates Network (GCN) and theInterplanetary Network. Notifications of astrophysical transients are sent worldwide instantly from KONUS, and are of importance in the subsequent positioning of telescopes everywhere. Thus, the instrument remains an active contributor to the astrophysical community, for instance, with theNeil Gehrels Swift Observatory (Swift mission).
The TGRS instrument was shut off early in the mission due to the planned expiration of coolant.
The Energetic Particles: Acceleration, Composition and Transport (EPACT)[7] investigation consists of multiple telescopes including: the Low Energy Matrix Telescope (LEMT); SupraThermal Energetic Particle telescope (STEP); and ELectron-Isotope TElescope system (ELITE). ELITE is composed of two Alpha-Proton-Electron (APE) telescopes and an Isotope Telescope (IT).
The highest energy telescopes (APE and IT) failed early in the mission, though APE does two channels of ~5 and ~20 MeVprotons but IT was turned off. However, LEMT (covering energies in the 1–10 MeV/nucl range) and STEP (measuring ions heavier than protons in the 20 keV–1 MeV/nucl range) still continue to provide valuable data.
The Solar Wind and Suprathermal Ion Composition Experiment (SMS)[6] onWind is composed of three separate instruments: SupraThermal Ion Composition Spectrometer (STICS); high-resolution mass spectrometer (MASS); and Solar Wind Ion Composition Spectrometer (SWICS). STICS determines the mass, mass per charge, and energy for ions in the energy range of 6–230 keV/e. MASS determines elemental and isotopic abundances from 0.5 to 12 keV/e. SWICS determines mass, charge, and energy for ions in the energy range of 0.5 to 30 keV/e. The SWICS "stop"microchannel plate detector (MCP) experienced a failure resulting in reduced capabilities for this instrument and was eventually turned off in May 2000. The SMS data processing unit (DPU) experienced a latch-up reset on 26 June 2009, that placed the MASS acceleration/deceleration power supply into a fixed voltage mode, rather than stepping through a set of voltages. In 2010, MASS experienced a small degradation in the acceleration/deceleration power supply which reduced the efficiency of the instrument, though this does not seriously affect science data analysis.
First statistical study of high frequency (≥1 kHz) electric field fluctuations in the ramp ofinterplanetary (IP) shocks.[18] The study found that the amplitude ofion acoustic waves (IAWs) increased with increasingfast modeMach number andshock compression ratio. They also found that the IAWs had the highest probability of occurrence in theramp region.
Observation of the largest whistler wave using a search coil magnetometer in theradiation belts.[19][20]
First observation ofshocklets upstream of a quasi-perpendicular IP shock.[14]
First simultaneous observations ofwhistler mode waves with electron distributions unstable to the whistlerheat flux instability.[14]
First evidence to suggest that the observed bi-polar ES structures in the shock transition region are consistent withBGK modes or electronphase space holes.[23]
First evidence of a correlation between the amplitude of electron phase space holes and the change in electron temperature.[24]
First evidence of three-wave interactions in the terrestrialforeshock using bi-coherence.[25][26]
First evidence of Alfvén-cyclotron dissipation.[28]
First (shared withSTEREO spacecraft) observation of electron trapping by a very large amplitude whistler wave in theradiation belts (also seen in STEREO observations).[29][30]
First observation of Langmuir and whistler waves in thelunar wake.[31]
First evidence of local field-aligned ion beam generation byforeshock electromagnetic waves called short large amplitude magnetic structures or SLAMS, which aresoliton-like waves in themagnetosonic mode.[33]
Observation of interplanetary andinterstellar dust particle impacts, with over 100,000 impacts recorded as of 2019.[3]
First observation of a giant flare — emission of greater apparent intensity thangamma ray bursts with an average occurrence rate of once per decade — within the nearbySculptor Galaxy. The press release can be found atGiant Flare in Nearby Galaxy. This work led to at least six papers published inNature.
Wind spacecraft in fairing on Delta II launch vehicle waiting for launch.
Wind continues to produce relevant research, with its data having contributed to over 5370 publications since 1 January 2010 and over 2480 publications prior. As of 28 March 2025 (not including 2025 publications), the total number of publications either directly or indirectly usingWind data is ~7856, or an average of ~262 publications/year (the average since 2020 is ~493 publications/year or ~2464 publications since 2020).[2]Wind data has been used in over 130 high impact refereed publications with ~16 inScience, ~81 inNature Publishing Group (includesNature,Nature Physics,Nature Communications,Scientific Reports, andScientific American), and ~38 inPhysical Review Letters. Many of these publications utilizedWind data directly and indirectly by citing the OMNI dataset at CDAWeb, which relies heavily uponWind measurements.[35]
An April 2012 paper makes NASA's homepage news.[36]
A March 2013 paper using data from theWind spacecraft was highlighted as aPhysical Review Letters Spotlight article and a NASA Feature Article.[37][38]
An April 2013 paper was highlighted on the NASA website.[39]
Wind celebrated the 20th anniversary of its launch on November 1, 2014, highlighted on NASA's homepage.[42]
A November 2016 paper primarily usingTHEMIS observations and utilizing data from theWind spacecraft was published inPhysical Review Letters and selected as an Editors' Suggestion article, and was highlighted on the NASA and THEMIS Science Nuggest sites.[43][44][45]
Wind data was used in a June 2019 paper showing that ions are heated in a preferential zone close to the solar surface, at altitudes that will be visited byParker Solar Probe in roughly two years.[46][47]
Wind celebrated the 25th anniversary of its launch on 1 November 2019, highlighted in a NASA feature article.[3]
Wind/ KONUS data helped to detect one of the strongest/brightestgamma-ray burst (GRB) events on record, with a total energy output of 1054 ergs (or 1047 J). The story is highlighted on 13 October 2022 atExceptional Cosmic Blast.
Wind celebrated the 28th anniversary of its launch on 1 November 2022.
On 21 February 2023 theWind review paper[34] published inReviews of Geophysics was awarded as aTop Cited Article 2021-2022 by the journal.
TheWind Operations Team at NASA's Goddard Space Flight Center received the AIAA Space Operations & Support Award on 2 September 2015. The award honors the team's "exceptional ingenuity and personal sacrifice in the recovery of NASA'sWind spacecraft".[49] Jacqueline Snell, engineering manager for theWind,Geotail, andAdvanced Composition Explorer (ACE) missions, accepted the award on behalf of the team.[50]
^abcdvon Rosenvinge, T. T.; et al. (February 1995). "The Energetic Particles: Acceleration, Composition, and Transport (EPACT) investigation on the WIND spacecraft".Space Science Reviews.71 (1–4):155–206.Bibcode:1995SSRv...71..155V.doi:10.1007/BF00751329.S2CID117444106.
^Wilson III, L.B.;Cattell; Kellogg; Wygant; Goetz; Breneman; Kersten; et al. (January 2011). "A statistical study of the properties of large amplitude whistler waves and their association with few eV to 30 keV electron distributions observed in the magnetosphere by Wind".arXiv:1101.3303 [physics.space-ph].
^Bale, S.D.; et al. (1996). "Phase coupling in Langmuir wave packets: Possible evidence of three-wave interactions in the upstream solar wind".Geophys. Res. Lett.23 (1):109–112.Bibcode:1996GeoRL..23..109B.doi:10.1029/95GL03595.
Launches are separated by dots ( • ), payloads by commas ( , ), multiple names for the same satellite by slashes ( / ). Crewed flights are underlined. Launch failures are marked with the † sign. Payloads deployed from other spacecraft are (enclosed in parentheses).
This article incorporates text from this source, which is in thepublic domain.
