Minimize WIND

WIND Solar-Terrestrial Mission

WIND is a NASA/GSFC solar-terrestrial mission within the US GGS (Global Geospace Science) initiative and also part of the ISTP (International Solar-Terrestrial Physics) program. The objective is to study sources, acceleration mechanisms and propagation processes of energetic particles and the solar wind. Investigation of solar wind mass momentum and energy) with input first from the day-side double lunar swingby orbit, and later from a small halo orbit at L1. WIND, together with GEOTAIL (ISAS, Japan, launch 1992), Polar (NASA, launch 1996), SOHO (ESA/NASA, launch 1995), and the Cluster constellation spacecraft (ESA, launch 2000), constitute the cooperative scientific ISTP program. 1)

The science objectives are:

• 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 from the Ulysses spacecraft.


Figure 1: Artist's illustration of the WIND spacecraft (image credit: NASA)


WIND is a spin-stabilized S/C at 20 rpm with the spin axis normal to the ecliptic plane. The spacecraft shape is a cylinder of size: 2.4 m diameter and 1.8 m in height. Surface-mounted solar arrays provide 370 W of power, including 144 W for payload instruments. The Wind S/C was built by Martin Marietta Astro Space of Princeton, NJ. Total S/C mass at launch = 1250 kg (300 kg of hydrazine propellant, 195 kg science payload). Nominal lifetime = 3 years (min).

The spacecraft exhibits very favorable EMI/EMC (Electromagnetic Interference/Electromagnetic Compatibility) levels. The wire antennas are 100 m and 15 m tip-to-tip, respectively. The axial antennas are about 12 m tip-to-tip. Each boom is 12 m in length.


Figure 2: Line drawing of the WIND spacecraft with instrument locations (image credit: NASA)

RF communications: On-board recording capability of 1.3 Gbit (digital tape recorder). Transmission via DSN (Deep Space Network) for 2 hr nominal daily contact periods. Science data rates: 5.6 kbit/s realtime and 128 kbit/s playback data. The WIND S/C provides on-board interconnection of instrumentation for data communication. Data sharing among the instruments can be triggered by pattern recognition schemes of the on-board computers.


Launch: WIND was launched Nov. 1, 1994 with a Delta II vehicle from Cape Canaveral, FLA.

WIND orbits:

1) WIND was initially placed in a double-lunar-swingby orbit near the ecliptic plane with an apogee from 80 to 250 RE and a perigee of 5 to 10 RE during first two years (inclination = 19.6º). In this orbit, lunar gravity assists were used to keep the apogee over the day hemisphere of the Earth, and magnetospheric observations were made. 2)


Figure 3: Overview of the original mission orbit (image credit: NASA)

2) WIND extended mission. In Nov. 1996, WIND was inserted into a ”halo” orbit, about the sunward Sun-Earth gravitational equilibrium point (Lagrangian point L1), varying from 235 to 265 RE. In this orbit WIND measures the incoming solar wind, magnetic fields and particles continuously and provides an approximately one-hour warning to the other ISTP spacecraft of changes in the solar wind.


Figure 4: WIND extended mission April 1998-April 1999 (image credit: NASA) 3)



Status of mission:


• In 2014, the WIND spacecraft and its payload are operating 'nominally'. The Wind mission has been extended nominally for ten years, but of course, funding is only provided till the next Senior Review in two years. Also, all is contingent on the continued healthy operation of the spacecraft. 4)

WIND is a venerable spacecraft approaching its 20th year of operations. Currently in L1 halo upstream of Earth, WIND carries a comprehensive package of instruments to measure the plasma and fields around the spacecraft, including energetic particles and radio waves.
The spacecraft and instruments are in good health and WIND continues to be a remarkably productive mission scientifically. By acting as a near Earth measurement point and reference for comparison with other spacecraft in terms of solar wind and energetic particle data, Wind enables multi-point ICME analyses and studies of energetic particle acceleration processes. In addition, the mission’s long solar wind and field data sets have recently been re-analyzed by the instrument teams, producing ground breaking discoveries regarding fundamental plasma processes such as instabilities, wave particle interactions, shocks, and reconnection, which are directly relevant to NASA’s heliospheric research objectives. 5)

• In 2013, the WIND spacecraft and its payload are operating 'nominally'. Equipped with heavy shielding and double-redundant systems to safeguard against failure, the spacecraft was built to last. The WIND mission has survived almost two complete solar cycles and innumerable solar flares. 6) 7) 8)

Using data from an aging WIND spacecraft of NASA, researchers have found signs of an energy source in the solar wind that has caught the attention of fusion researchers. NASA will be able to test the theory later this decade when it sends a new probe into the sun for a closer look (Ref. 6).

The discovery was made by a group of astronomers trying to solve a decades-old mystery: What heats and accelerates the solar wind?

The solar wind is a hot and fast flow of magnetized gas that streams away from the sun's upper atmosphere. It is made of hydrogen and helium ions with a sprinkling of heavier elements. Researchers liken it to the steam from a pot of water boiling on a stove; the sun is literally boiling itself away.

But the solar wind does something that steam in the kitchen never does. As steam rises from a pot, it slows and cools. As solar wind leaves the sun, it accelerates, tripling in speed as it passes through the corona. Furthermore, something inside the solar wind continues to add heat even as it blows into the cold of space.

Finding that "something" has been a goal of researchers for decades. In the 1970s and 80s, observations by two German/US Helios spacecraft set the stage for early theories, which usually included some mixture of plasma instabilities, magnetohydrodynamic waves, and turbulent heating. Narrowing down the possibilities was a challenge. The answer, it turns out, has been hiding in a dataset from one of NASA's oldest active spacecraft, a solar probe named Wind.


Figure 5: An artist's concept of the Wind spacecraft sampling the solar wind. Justin Kasper's science result is inset (image credit: NASA)

The source of the heating in the solar wind is ion cyclotron waves. Ion cyclotron waves are made of protons that circle in wavelike-rhythms around the sun's magnetic field. According to a theory developed by Phil Isenberg (University of New Hampshire) and expanded by Vitaly Galinsky and Valentin Shevchenko (UC San Diego), ion cyclotron waves emanate from the sun; coursing through the solar wind, they heat the gas to millions of degrees and accelerate its flow to millions of miles per hour. - Justin Kasper of the Harvard-Smithsonian Center for Astrophysics, Massachusetts, and collaborators present a model that demonstrates how certain plasma waves, called ion cyclotron waves, will preferentially heat heavier ions travelling below a threshold velocity. Kasper's findings confirm that ion cyclotron waves are indeed active, at least in the vicinity of Earth where the WIND spacecraft operates. 9) 10)

Plasma carrying a spectrum of counterpropagating field-aligned ion-cyclotron waves, can strongly and preferentially heat ions through a stochastic Fermi mechanism. Such a process has been proposed to explain the extreme temperatures, temperature anisotropies, and speeds of ions in the solar corona and solar wind. The team of researchers quantified, how differential flow between ion species results in a Doppler shift in the wave spectrum, that can prevent this strong heating. Two critical values of differential flow were derived for strong heating of the core and tail of a given ion distribution function. The comparison of these predictions to observations from the Wind spacecraft reveals excellent agreement. Solar wind helium, that meets the condition for strong core heating, is nearly 7 times hotter than hydrogen on average. Ion-cyclotron resonance contributes to heating in the solar wind, and there is a close link between heating, differential flow, and temperature anisotropy (Ref. 10).

• In 2012, the WIND spacecraft and its payload are operating 'nominally' in their 18th year on orbit. 11)

• The WIND spacecraft is operating almost nominally in 2010 (more than 16 years after launch). It passed the last two Senior reviews and is now in orbit around L1, out of phase with ACE. It will probably last until something goes wrong with the tape recorder, which is not solid state. The following arguments represent a rationale for continuing the Wind mission: 12) 13) 14)

- Wind continues to provide unique and robust solar wind measurements

- Wind is a 3rd solar wind vantage point for STEREO providing a backup capability and enhanced science return for 3-point studies

- Wind and ACE together provide a reasonable probability of maintaining near-Earth solar wind monitoring capabilities for NASA into the next decade

- Wind and ACE are complementary not identical. Thus both are needed to continue to provide complete near-Earth, 1 AU baseline observations for current and future NASA deep space missions.

- Wind’s scientific productivity remains high and its observations continue to lead to significant scientific discoveries for all three research objectives of NASA’s SMD (Science Mission Directorate).

• In 2008, the Wind spacecraft continues to operate in very good health. In 2000, the mission team successfully reconfigured the communications system to enhance the telemetry margin. Reliance on a single digital tape recorder since 1997 has never hampered operations, and the team took measures to minimize its use in order to extend tape recorder life as long as possible.

Seven of the eight Wind instruments, and all of the particles and fields instruments, remain largely or fully operational. Specifically, the EPACT, high energy particle and SMS solar wind composition instruments suffered some degradation, but both continue to provide valuable measurements. The SWE electron instrument required some reconfiguration to maintain its capabilities and the TGRS γ-ray detector, well beyond its design life, has been turned off.




The sensor complement allows the constant monitoring of the solar wind plasma, energetic particles, magnetic fields, radio and plasma waves found in the interplanetary medium as well as cosmic gamma ray bursts. 15)


MFI (Magnetic Field Investigation):

MFI PI: R. Lepping, NASA/GSFC. Objectives: investigation of the structure and fluctuations of the interplanetary magnetic field (transport of energy and acceleration of particles in the solar wind). Instrument: Magnetometer measures the intensity and direction of magnetic field vector. The MFI instrument consists of dual triaxial fluxgate magnetometers mounted on a 12 m radial boom, and a data processing and control unit within the spacecraft bus. The magnetometer sensors each produce analog signals proportional to the strength of the magnetic field component aligned with the sensor. These signals are then digitized and processed by a microprocessor controlled data system.

Instrument type

Dual, triaxial fluxgate magnetometers (boom mounted)

Dynamic ranges (8)

±4 nT by ground command; ±16 nT; ±64 nT, 256 nT; ±1024 nT; ±4096 nT; ±16,384 nT; ±65,536 nT

Digital resolution (12 bit)

±0.001 nT; ±0.004 nT; ±0.016 nT; ±0.0625 nT; ±0.25 nT; ±1.0 nT; ±4 nT; ±16 nT

Sensor noise level

< 0.006 nT rms, 0-10 Hz

Sampling rate

44 vector samples/s in snapshot memory and 10.87 vector samples/s standard

Signal processing

FFT processor, 32 logarithmically spaced channels, 0 to 22 Hz. Full spectral matrices generated every 46 s (low rate) or 23 s (high rate) for four time series (Bx, By, Bx, /B/)

FFT windows/filters

Full despin of spin plane components, 10% cosine taper, Hanning window, first difference filter

FFT dynamic range

72 dB, µ-law Log-compressed, 13 bit normalized to 7 bit + sign

Snapshot memory capacity

256 kbit

Trigger modes (3)

Overall magnitude ratio, directional max-spin peak to peak change, spectral increase across frequency band (rms)

Telemetry modes (3)

Three, selectable by ground command


Sensors (2): 450 gram; Electronics (redundant): 2.1 kg

Power consumption

2.4 W

Table 1: Summary characteristics of the MFI instrument


Figure 6: Illustration of the MFI instrument (image credit SSL/UCB)


WAVES (Radio and Plasma Wave Experiment):

WAVES PI: J. Bouqeret, Observatoire de Meudon, France. WAVES was built as a joint effort of the Paris-Meudon Observatory, the University of Minnesota, and the Goddard Space Flight Center (GSFC). Objectives: measurement of the radio and plasma wave phenomena over a very wide frequency range which occur in the solar wind. Specific objectives call for:

• Low-frequency electric waves and low-frequency magnetic fields, from DC to 10 kHz

• Electron thermal noise, from 4 kHz to 256 kHz

• Radio waves, from 20 kHz to 14 MHz

• Time domain waveform sampling, to capture short duration events which meet quality criteria set into the WAVES data processing unit (DPU).

The sensors are: 16) 17)

1) Three electric dipole antenna systems provided by Fairchild Space (two are coplanar, orthogonal wire dipole antennas in the spin-plane, the other a rigid spin-axis dipole). The longer and shorter spin plane dipoles have lengths of 50 m and 7.5 m for each wire, respectively, while each spin-axis dipole extends 5.28 m from the top and bottom surfaces of the spacecraft.

2) Three magnetic search coils mounted orthogonally (designed and built by the University of Iowa). The triaxial magnetic search coil for measuring bi-frequency magnetic fields is mounted at the outboard end of a 12 m radial boom.

WAVES instrument elements: There are five main receiver systems: a bi-frequency (DC to 10 kHz) Fast Fourier Transform receiver, a broadband (4 kHz to 256 kHz) electron thermal noise receiver, two swept-frequency radio receivers (20 kHz to l MHz, and l MHz to 14 MHz), and a time domain waveform sampler (up to 120,000 samples per second). The DPU controls and acquires data from all operations of the experiment, and can be reprogrammed from the ground. The receiver systems and DPU are housed within the spacecraft body. WAVES has onboard interconnects with 3-D PLASMA and with SWE.

Note: In Table 2 the spin-plane electric antennas are referred to as Ex and Ey, the axial electric antenna as Ez and the 3 search coil magnetic axes as Bx, By and Bz.

Low Frequency FFT Receiver (FFT)



Frequency range

No channels


Dynamic range

Low band

4 of Ex, Ey, Ez, Bx, By or Bz

0.3 Hz - 170 Hz


250 µV (rms)

72 dB

Mid Band

4 of Ex, Ey, Ez, Bx, By or Bz

7 Hz - 3.5 kHz


10 µV (rms)

110 dB

High band

2 of Ex, Ey or Ez

20 Hz - 10 kHz


1 µV (rms)

128 dB

Thermal Noise Receiver (TNR)



Frequency range

No channels




Ex, Ey or Ez

20 kHz-1,040 kHz

32 or 16 /band (5 bands)

7 nV/Sqrt(Hz)

400 Hz-6.4 kHz

Radio Receiver Band 1 (RAD1)


Ex+Ez, Ez

20 kHz-1,040 kHz


7 nV/Sqrt(Hz)

3 kHz

Radio Receiver Band 2 (RAD2)


Ey+Ez, Ez

1.075 MHz-13.825 MHz


7 nV/Sqrt(Hz)

20 kHz

Time Domain Sampler (TDS)



Sample rate



Dynamic range

Fast sampler

2 of Ex, Ey or Ez

up to 120 ksample/s per channel

2 Mbit

80 µV (rms)

90 dB

Slow sampler

4 of Ex, Ey, Ez, Bx, By or Bz

up to 7.5 ksample/s per channel

2 Mbit

80 µV (rms)

90 dB

Table 2: Summary of the WAVES instrument characteristics


SWE (Solar Wind Experiment):

SWE PI: K. Ogilvie, GSFC. The instrument development is a joint effort of GSFC, UNH (University of New Hampshire), and MIT (Massachusets Institute of Technology). Objectives: measurement ions and electrons in the solar wind and the foreshock regions. Rates of once per minute for ions and 20 times per minute for electrons. Deduction of solar wind velocity, density, temperature, and heat flux. Specific measurement objectives are: 18) 19)

- To provide high time-resolution 3-D velocity distributions of the ion component of the solar wind, for ions with energies ranging from 200 eV to 8.0 keV

- High time-resolution 3-D velocity distributions of subsonic plasma flows including electrons in the solar wind and diffuse reflected ions in the foreshock region, with energies ranging from 7 eV to 22 keV

- High angular resolution measurements of the ”strahl” (beam) of electrons in the solar wind, along and opposite the direction of the interplanetary magnetic field, with energies ranging from 5 eV to 5 keV.

The SWE instrument consists of five integrated sensor/electronics boxes and a data processing unit (DPU). The sensor units are mounted on the top and bottom shelves of the spacecraft, extending through the top and bottom surfaces. The 3-D velocity distribution measurements of the ion component in the solar wind are made by a pair of Faraday cup analyzers, which provide a wide field-of-view and the capability for flow characterization within one spin revolution (3 seconds).

• The SWE instrument includes 2 Faraday cup ion detectors provided by MIT. The Faraday cups provide measurements of the solar wind protons and alpha particles at energy/charge up to 8 keV. The Faraday cup sensor contains a series of wire-mesh, planar grids knitted from tungsten wire and one or more collector plates. The velocity distribution function of ions is measured by applying a sequence of voltages to the ”modulator” grid. With voltage V applied to the grid, only particles having energy/charge (E/Q), greater than V will be able to pass through the grid and continue on to strike the collector plate where they produce a measurable current.

• VEIS (Vector Electron Ion Spectrometers). VEIS of the SWE instrument consists of an array of detectors built by NASA/GSFC for characterizing the solar wind electrons. The SWE on-board data system was provided by UNH. The 3-D velocity distribution measurements of ions and electrons in plasmas having Mach numbers < 1 are made using six cylindrical electrostatic deflection analyzers arranged in two triaxial sets.

• The SWE Strahl sensor consists of a toroidal electrostatic analyzer with channel-plate detectors. The objective is to measure the solar wind strahl, the narrow beam of electrons which travel outward from the sun closely aligned with the interplanetary magnetic field. During one 3 s rotation of the spacecraft, the strahl sensor makes high angular resolution measurements of the electron velocity distribution within a field of view 50º x 50º centered on the average magnetic field direction looking toward the sun, and one-half rotation later, measurements are made along the average field direction looking away from the sun. The measurement range is from 5 eV to 5 keV.


Figure 7: Vector electron ion spectrometer of SWE (image credit: NASA)


Figure 8: Faraday cup of SWE (image credit: NASA)


Figure 9: The Strahl detector of SWE (image credit: NASA)


EPACT (Energetic Particles Acceleration, Composition, Transport):

EPACT PI: T. T. von Rosenvinge, NASA/GSFC. Objectives: investigation of the elemental and isotopic abundances of the minor ions making up the solar wind with energies in excess of 20 keV. Measurements at a rate of once per minute for ions and 20 times per minute for electrons. Deduction of solar-wind velocity, density, temperature, and heat flux. 20)

The EPACT assembly consists of multiple telescopes that also provide a level of protection against single-point failures. The LEMT (Low Energy Matrix Telescope) consists of three identical telescopes, whereas ELITE (Electron Isotope Telescope) consists of two APE (Alpha-Proton-Electron) telescopes and an IT (Isotope Telescope). LEMT and ELITE have been designed, built and tested by the Low Energy Cosmic Ray Group and the Electronics Systems Branch of the Laboratory for High Energy Astrophysics at NASA/GSFC. Later, the STEP (Suprathermal Energetic Particle telescope system) was added to EPACT. STEP contains two identical telescopes. STEP was designed and built by the University of Maryland.

The APE and IT instruments are contained in a single package known as the ELITE. These solid state detector telescopes all use the dE/dx by E method of particle identification, except STEP, which obtains particle mass by measuring time-of-flight and energy. An onboard recorder allows continuous observations to be made.


Figure 10: Illustration of the LEMT assembly (image credit: NASA)


Figure 11: Illustration of ELITE (image credit: NASA)


Figure 12: The STEP (Supra Thermal Energetic Particle) telescope (image credit: NASA)

SMS (Solar Wind Ion Composition Study), the Mass Sensor, and Suprathermal Ion Composition Study). SMS is consisting of: SWICS (Solar Wind Ion Composition Spectrometer), STICS (Suprathermal Ion Composition Spectrometer) and MASS (Mass Resolution Spectrometer); PI: G. Gloeckler, University of Maryland. Science objectives: determine the abundance, velocity, spectra, temperature, and thermal speeds of solar-wind ions (plasma investigations in conjunction with EPACT) entering Earth's magnetosphere. The following measurements are obtained: 21)

- Energy, mass and charge composition of major solar wind ions from H to Fe, over the energy range from 0.5 to 30 keV/e (SWICS)

- High mass-resolution elemental and isotopic composition of solar wind ions from He to Ni, having energies from 0.5 to 12 keV/e (MASS)

- Composition, charge state and 3-D distribution functions of suprathermal ions (H to Fe) over the energy range from 8 to 230 keV/e (STICS).

The SMS experiment consists of five separate packages mounted on the spacecraft body. SWICS uses electrostatic deflection, post-acceleration, and a time-of-flight vs. energy measurement to determine the energy and elemental charge state composition of solar wind ions.

MASS uses energy/charge analysis followed by a time of flight measurement, to determine solar-wind ion composition with high mass-resolution (M/delta M > 100), for the first time.

STICS, similar to SWICS but not using post-acceleration, has a large geometric factor and wide angle viewing for studies of suprathermal ions.


Figure 13: Schematic side view of the SWICS instrument (image credit: University of Maryland)


Figure 14: Schematic side view of the MASS instrument (image credit: University of Maryland)


PLASMA (3-D Plasma and Energetic Particles Experiment):

PLASMA PI: R. Lin, SSL/UCB (Space Science Laboratory/University of California, Berkeley). Objectives: measurement of ions and electrons with energies above that of the solar wind and into the energy particle range. Energy range: 0.03 - 30 keV, sampling rate: 20 times per minute; wide angular coverage, good directional sensitivity. Study of particles in the bow shock and in the foreshock regions. 22)


Figure 15: Illustration of the PLASMA instrument (image credit: UCB)

PLASMA consists of three basic elements, each is designed to cover a different part of the suprathermal particle population.

• SST (Semiconductor Telescopes)

• EESA (Electron Electrostatic Analyzers)

• PESA (Ion Electrostatic Analyzers)

In addition, a Fast Particle Correlator (FPC) combines electron data from the electron analyzer with plasma wave data from the WAVES experiment to study wave-particle interactions.

To avoid effects of the spacecraft potential on the low energy particle detection, EESA-L and EESA-H are mounted on the end of a 0.5 m boom, while PESA-L, PESA-H and the SSTs are mounted on the end of an opposing 0.5 m boom.

Electrostatic Analyzers



Energy range


Geometric factor



100 eV to 30 keV

360º x 90º

0.1 E cm2 sr



3 eV to 30 keV

180º x 14º

1.3 e-2 E cm2 sr



3 eV to 30 keV

360º x 14º

1.5 e-2 E cm2 sr



3 eV to 30 keV

180º x 14º

1.6 e-4 E cm2 sr

Semiconductor Detector Telescopes

Foil F


25 eV to 400 keV

180º x 20º

1.7 cm2 sr

Magneto O


20 keV to 6 MeV

180º x 20º

1.7 cm2 sr

Telescope FT


400 keV to 1 MeV

72º x 20º

0.36 cm2 sr

Telescope OT


6 MeV to 11 MeV

72º x 20º

0.36 cm2 sr

Table 3: Specification of the PLASMA instrument

The default mode of operation of the WIND 3-D experiment includes the following features:

- PESA and EESA detectors are swept over their energy range 32 or 64 times per spacecraft spin. Moments (density, velocity, pressure tensor, heat flux) computed on-board, three dimensional distributions with various energy and angular resolutions, and pitch angle distributions are telemetered

- SST data are collected 16 times per spin for 16 or 24 energy channels. Spectra and three dimensional distributions are computed and telemetered at rates depending on the energy band (higher rates for the higher-flux lower energies), and pitch angle distributions are computed.

- Another special mode involves use of the FPC which performs three types of correlation: direct wave-particle correlations, auto-correlations, and burst correlations.


TGRS (Transient Gamma Ray Spectrometer):

TGRS PI: B. Teegarden, NASA/GSFC. TGRS is a collaboration between GSFC and CNRS/CESR (CNRS/Centre d'Etude Spatiale des Rayonnements), Toulouse, France. Objectives: observation of transient gamma-ray events, spectroscopic survey of cosmic gamma-ray transients, measurements of gamma-ray lines in solar flares. Specific measurement objectives are: Measurement ranges: 15 keV - 8.2 MeV. 23) 24) 25)

- Spectroscopic measurements of transient gamma-ray events, in the energy range from 15 keV to 10 MeV with an energy resolution of 2.0 keV @ 1.0 MeV (E/delta E = 500)

- Monitoring of the time variability of the 511 keV line emission from the galactic center, on time scales from ~2 days to >1 year.

The TGRS instrument consists of four assemblies: detector cooler assembly, pre-amp, and analog processing unit, all mounted on a tower on the +Z end of the spacecraft, and a digital processing unit mounted in the body of the spacecraft. The detector is a 215 cm3 high purity n-type germanium crystal of dimensions: 6.7 cm (diameter) x 6.1 cm (length), sensitive to energies in the 20-8000 keV band. The detector is kept at its operating temperature of 85 K by a passive radiative cooler (a two-stage cooler surrounds the detector, providing a field of view of 170º). The resolution of TGRS at 500 keV is about 2 keV FWHM (Full Width at Half Maximum). The TGRS detector has no active shielding and is permanently exposed to ~1.8 steradian of the southern Galactic hemisphere which is unobstructed by the cooler. The radiation environment experienced by TGRS is dominated by two components: diffuse cosmic hard X and gamma radiation, and Galactic cosmic rays.

The germanium detector serves as a reaction medium for incoming gamma rays, which, depending on their energy, are either stopped by or passed through the detector crystal. Particle energy and angle of incidence are calculated based on a number of primary and secondary interaction processes, including photoelectric, Compton, pair and bremsstrahlung radiation as well as the ionization energy losses of secondary electrons.

When a burst or flare occurs, the instrument switches to a burst mode, where each event in the detector is pulse-height analyzed and time tagged in a burst memory. Then the instrument switches to a dump mode for reading out the burst memory.


KONUS (Gamma Ray Burst Investigation):

KONUS PIs: E. Mazets/T. Cline, Ioffe Physical Technical Institute, St. Petersburg, Russia. The GSFC instrument is sponsored by Russia. Science objectives: studies of gamma-ray burst and solar flares in the energy range 10 keV to 10 MeV (similar to the TGRS studies). KONUS has a lower resolution than TGRS but a broader coverage to complement TGRS. KONUS also performs event detection and measures time history. The measurement objectives are: 26)

- Monitoring of gamma-ray burst (GRB) energy spectra over the energy range 10 keV to 10 MeV, with energy resolution E/delta E = 15 @ 200 keV

- Measurement of burst time histories in three energy ranges covering 10 to 770 keV

- High-time-resolution measurement (2 ms resolution) for the high-intensity sections of a burst time history

- Continuous measurement of the gamma ray and cosmic ray background, interrupted only to read out bursts.

The Konus instrument consists of two Russian sensors mounted on the top and bottom of the spacecraft aligned with the spin axis, a U.S. interface box, and a Russian electronics package mounted in the spacecraft body. The sensors, copies of ones successfully flown on the Soviet COSMOS, VENERA and MIR missions, are identical and interchangeable Nal scintillation crystal detectors of 200 cm2 area, shielded by Pb/Sn. The design and location of the two sensors ensure practically isotropic angular sensitivity. The relative count rates recorded by the two detectors provide a burst source locus to within a few degrees relative to the spin axis. Onboard analysis of background and burst events is performed by four pulse height analyzers, four time history analyzers, two high resolution time history analyzers and a background measurement system.





4) Information provided by Adam Szabo, the WIND Mission Scientist at NASA/GSFC.

5) William Lotto, Doug Brain, Jim Drake, Joe Fennel, Richard R. Fisher, Joe Jaclin, Tim Hobey, Bob McCoy, Mark Mold win, Alexei Pervasive, John Plane, Howard Singer, Charles Swen son, “Senior Review 2013 of the Mission Operations and Data Analysis Program for the Heliophysics Extended Missions,” NASA, June 13, 2013, p. 63, URL:

6) Tony Pillips, “Solar Wind Energy Source Discovered,” NASA Science News, March 8, 2013, URL:


8) Adam Szabo, Lynn B. Wilson III, “Wind 2013 Senior Review Proposal,” Executive Summary, URL:

9) Justin C. Kasper, Bennett A. Maruca, Michael L. Stevens, Arnaud Zaslavsky, “Sensitive Test for Ion-Cyclotron Resonant Heating in the Solar Wind,” Physical Review Letters, Vol. 110, Issue 9, 091102, Feb. 28, 2013, URL:

10) Justin C. Kasper, Bennett A. Maruca, Michael L. Stevens, Arnaud Zaslavsky, “Sensitive Test for Ion-Cyclotron Resonant Heating in the Solar Wind,” Physical Review Letters, Vol. 110, Issue 9, 091102, Feb. 28, 2013, URL:


12) Information provided by Adam Szabo and Keith W. Ogilvie of NASA/GSFC.

13) Adam Szabo, Michael R. Collier, “WIND - 2008 Senior Review Proposal,” URL:


15) “Wind Instrument Desciptions,” URL:

16) J.-L. Bougeret, M. L. Kaiser, P. J. Kellogg, R. Manning, K. Goetz, S. J. Monson, N. Monge, L. Friel, C. A. Meetre, C. Perche, L. Sitruk, S. Hoang, “WAVES: The Radio and Plasma Wave Investigation on the WIND Spacecraft,” Space Science Review, Vol. 71, No. 5, 1995, URL:


18) K. W. Ogilvie, D. J. Chorney, R. J. Fitzenreiter, F. Hunsaker, J. Keller, J. Lobell, G. Miller, J. D. Scudder, E. C. Sittler Jr., R. B. Torbert, D. Bodet, G. Needell, A. J. Lazarus, J. T. Steinberg, J. H. Tappan, A. Mavretic, E. Gergin, “SWE, a Comprehensive Plasma Instrument for the Wind Spacecraft,” Space Science Reviews, Vol. 71, No 5, 1995, pp 55-77, URL:


20) T. T. von Rosenvinge, L. M. Barbier, J. Karsh, R. Liberman, M. P. Madden, T. Nolan, D. V. Reames, L. Ryan, S. Singh, H. Trexel, G. Winkert, G. M. Mason, D. C. Hamilton, P. Walpole, “The Energetic Particles: Acceleration, Composition, and Transport (EPACT) Experiment on the Wind Spacecraft,” Space Science Reviews, Vol. 71, No. 5, 1995, pp. 155-206, DOI: 10.1007/BF00751329


22) WIND 3-D Plasma and Energetic Particle Investigation Home Page,



25) A. Owens, R. Baker, T. L. Cline, N. Gehrels, J. Jermakian, T. Nolan, R. Ramaty, G. Smith,D. E. Stilwell, B. J. Teegarden, J. Trombka, H. Yaver, C. P. Cork, D. A. Landis, P. N. Luke, N. W. Maden, D. Malone, R. H. Pehl, K. Hurley,S. Mathias, A. H. Post Jr., “The Transient Gamma-Ray Spectrometer,” IEEE Transactions on Nuclear Science, Vol. 38, Issue 2, Apr. 1991, pp. 559-567


The information compiled and edited in this article was provided by Herbert J. Kramer from his documentation of: ”Observation of the Earth and Its Environment: Survey of Missions and Sensors” (Springer Verlag) as well as many other sources after the publication of the 4th edition in 2002. - Comments and corrections to this article are always welcome for further updates.

Minimize Related Missions

The co-operative ISTP program:

Complementary missions: