Solar and Heliospheric Observatory

Solar and Heliospheric Observatory (SOHO)

SOHO satellite
Names	SOHO
Mission type	Solar observation
Operator	ESA / NASA
COSPAR ID	1995-065A
SATCAT no.	23726
Website	sohowww.nascom.nasa.gov
Mission duration	2 years (planned) 28 years, 6 months and 1 day (in progress)
Spacecraft properties
Bus	SOHO
Manufacturer	Matra Marconi Space
Launch mass	1,850 kg (4,080 lb) [1]
Payload mass	610 kg (1,340 lb)
Dimensions	4.3 × 2.7 × 3.7 m (14.1 × 8.9 × 12.1 ft) 9.5 m (31 ft) with solar arrays deployed
Power	1500 watts
Start of mission
Launch date	2 December 1995, 08:08:01 UTC
Rocket	Atlas IIAS (AC-121)
Launch site	Cape Canaveral, LC-36B
Contractor	Lockheed Martin
Entered service	May 1996
Orbital parameters
Reference system	Sun–Earth L1 orbit
Regime	Halo orbit
Perigee altitude	206,448 km (128,281 mi)
Apogee altitude	668,672 km (415,494 mi)
Instruments CDS Coronal Diagnostic Spectrometer CELIAS Charge, Element, Isotope Analysis COSTEP Comprehensive Suprathermal & Energetic Particle Analyzer EIT Extreme UV Imaging Telescope ERNE Energetic and Relativistic Nuclei and Electron experiment GOLF Global Oscillations at Low Frequencies LASCO Large Angle Spectrometer Coronagraph MDI Michelson Doppler Imager SUMER Solar UV Measurement of Emitted Radiation SWAN Solar Wind Anisotropies UVCS UV Coronagraph and Spectrometer VIRGO Variability of Solar Irradiance and Gravity Oscillations
SOHO mission patch Horizon 2000 Huygens →

The Solar and Heliospheric Observatory (SOHO) is a European Space Agency (ESA) spacecraft built by a European industrial consortium led by Matra Marconi Space (now Airbus Defence and Space) that was launched on a Lockheed Martin Atlas IIAS launch vehicle on 2 December 1995, to study the Sun. It has also discovered over 5,000 comets.^[2] It began normal operations in May 1996. It is a joint project between the European Space Agency (ESA) and NASA. SOHO was part of the International Solar Terrestrial Physics Program (ISTP). Originally planned as a two-year mission, SOHO continues to operate after over 25 years in space; the mission has been extended until the end of 2025, subject to review and confirmation by ESA's Science Programme Committee.^[3]

In addition to its scientific mission, it is a main source of near-real-time solar data for space weather prediction. Along with Wind, Advanced Composition Explorer (ACE), and Deep Space Climate Observatory (DSCOVR), SOHO is one of four spacecraft in the vicinity of the Earth–Sun L1 point, a point of gravitational balance located approximately 0.99 astronomical unit (AU) from the Sun and 0.01 AU from the Earth. In addition to its scientific contributions, SOHO is distinguished by being the first three-axis-stabilized spacecraft to use its reaction wheels as a kind of virtual gyroscope; the technique was adopted after an on-board emergency in 1998 that nearly resulted in the loss of the spacecraft.