The Solar and Heliospheric Observatory – SOHO – carries a suite of instruments to study the Sun from its deep core to the outer corona and the solar wind

The Solar and Heliospheric Observatory – SOHO – carries a suite of instruments to study the Sun from its deep core to the outer corona and the solar wind

SOHO – for almost two decades the workhorse of ESA and NASA for many fields of solar science – is positioned in a halo orbit around the first Lagrangian point. This advantageous vantage allows to observe the Sun uninterrupted and without geocoronal disturbances. The SOHO payload is composed of 12 instruments, three helioseismology instruments (GOLF, VIRGO, MDI), two spectrometers (CDS, SUMER), a disk imager (EIT), two coronagraphs (UVCS, LASCO), three in-situ instruments (CELIAS, COSTEP, ERNE) and a solar wind mapper (SWAN). While some of the instruments have reached the end of their operational lifetime and transited into the data phase, others are fully operational. The LASCO coronagraph has even increased its importance for heliospheric science, since it serves as the third eye for the SECCHI instruments on STEREO. It is foreseen to operate SOHO at least into the early 2020s. So far SOHO has provided an unprecedented breadth and depth of information about the Sun, documented in an impressive, still growing body of  scientific and popular literature.

Instruments onboard SOHO

Instrument Measurements
GOLF: Global Oscillations at low Frequency
PI: A. Gabriel; Institute d'Astrophysique Spatiale, France
Global Sun velocity oscillations

VIRGO: Variability of solar Iradiance and Gravity Oscillations
PI: C. Fröhlich; PMOD World Radiation Center, Switzerland

Global Sun and low resolution imaging, active cavity radiometers
MDI/SOI: Michelson Doppler Imager / Solar Oscillations Investigation
PI: P.H. Scherrer;Center for Space Science and Astrophysics, Stanford, USA
Velocity oscillations, harmonic degree up to 4500
SUMER: Solar Ultraviolet Measurements of Emitted Radiation
PI: K. Wilhelm; Max-Planck-Institut für Sonnensystemforschung, Germany
Hires normal incidence spectrometer; 50 - 160 nm
CDS: Coronal Diagnostic Spectrometer
PI: Richard Harrison; Rutherford Appleton Laboratories, UK
Normal and grazing incidence spectrometers; 15 - 80 nm
EIT: Extreme-Ultraviolet Imaging Telescope
PI: J.-P. Delaboudiniere; Institute d'Astrophysique Spatiale, France
Full disk imager; evolution of chromospheric and coronal structures
UVCS: Ultraviolet Coronograph Spectrometer
PI: J.L. Kohl; Harvard CFA, USA
Coronal diagnostic between 1.3 and 10 R_sun
LASCO: Large Angle Spectroscopic Coronagraph
PI: G.E. Brueckner; Hulburt Center for Space Research, NRL, USA
Triple white-light coronagraph, 1.1 - 30 R_sun
SWAN: Solar Wind Anisotropies
PI: J.L. Berteaux; Service d'Aéronomie, CNRS, France
Scanning telescopes with hydrogen absorption cell for Ly-a light
CELIAS: Charge, ELement and Isotope Analysis System
PI: D. Hovestadt; Max-Planck-Institut für extraterrestrische Physik, Germany
Solar wind energy distribution and composition, 0.1 - 1000 keV/e
COSTEP: COmprehensive SuperThermal and Energetic Particle analyser
PI: R. Müller-Mellin; Institut für Kernphysik, Uni Kiel, Germany
Solar wind energy distribution of ions, 0.04 - 53 MeV/n
ERNE: Energetic and Relativistic Nuclei and Electron experiment
PI: J. Torsti; Space Research Laboratory, Turku, Finland
Solar wind energy distribution and isotopic composition,
p-Ni: 1.4 - 540 MeV/n; electrons: 5-60 MeV

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