Encyclopedia Astronautica
SOHO



soho.jpg
Soho
Credit: ESA
European solar satellite. One launch, 1995.12.02. SOHO was a component of the Collaborative Solar-Terrestrial Research (COSTR) Program of the International Solar Terrestrial Physics (ISTP) Program.

SOHO's specific objectives were to study and understand the solar corona, in particular its heating mechanism and its expansion into the solar wind; and to study the solar structure and interior dynamics from the Sun's core to the photosphere. SOHO had the first long duration unobstructed view of the sun from its halo orbit about the L1 Lagrange point 1.5 million kilometers ahead of the Earth. In this orbit, it avoided eclipses with the Earth that blocked the sun. The spacecraft was built by ESA, tracking and data acquisition were shared by NASA and ESA, and mission operations were conducted by NASA.

The spacecraft consisted of two modules and was three-axis stabilized to within 10 arcsec, with pointing stability of 1 arcsec per 15 minutes. The service module provided power, thermal and pointing control. The payload module contained twelve science instruments. Power was provided by dual solar panels, with a total output of 1150 W. The payload consumed 450 W on orbit. The velocity of the spacecraft relative to the sun was known to within 0.5 cm/sec.

Payloads:

  • GOLF (Global Oscillations at Low Frequencies) - studied the internal structure of the sun by measuring the spectrum of global oscillations in the frequency range 10-7 to 10-2 Hz.
  • VIRGO (Variability of Solar Irradiance and Gravity Oscillations) - provided continuous measurements of the solar total and spectral irradiance and spectral radiance variation, solar polar and equatorial diameters, and the frequencies, amplitudes and phases of oscillation modes in the frequency range of 1 uHz to 8 mHz
  • SOI/MDI (Solar Oscillations Investigation/ Michelson Doppler Imager) - used a telescope with a 1024*1024 CCD camera to image the Sun. Data from the experiment was used to understand the static and dynamic properties of the Sun's convection zone and core, as well as contributing to knowledge of the solar magnetic field.
  • SUMER (Solar Ultraviolet Measurements of Emitted Radiation) - measured profiles and intensities of extreme ultraviolet (EUV) lines emitted in the solar atmosphere. This data was used to understand plasma flow characteristics, turbulence and wave motions, plasma densities and temperatures, and structures and events associated with solar magnetic activity in the chromosphere, the transition zone and the corona.
  • CDS (Coronal Diagnostic Spectrometer) - designed to obtain spectra-spectroheliograms in a number of lines in the EUV frequency region.
  • EIT (Extreme Ultraviolet Imaging Telescope) - imaged the solar transition region and inner corona at 4 EUV frequencies (171, 195, 284, 304 angstroms). The instrument imaged active regions, filaments and prominences, coronal holes, coronal "bright points," polar plumes, and a variety of other solar features.
  • UVCS (Ultraviolet Coronograph Spectrometer) - imaged the solar corona between 2 and 10 solar radii. Spectrographic images were used to calculate proton velocity distribution, proton outflow velocity, electron temperature, and specific ion outflow velocities and densities.
  • LASCO (Large Angle Spectrometric Coronograph) - a set of three coronagraph telescopes that recorded white light and spectral images of the solar corona. Data from the experiment was used to understand how the corona was heated, how the solar wind was accelerated, what caused coronal transients, and how large-scale structures evolved.
  • CELIAS (Charge, Element and Isotope Analysis System) - studied the composition of the solar wind and solar and interplanetary energetic particles. It also monitored the absolute EUV flux from the Sun.
  • COSTEP (Comprehensive Suprathermal and Energetic Particle Analyzer)
  • ERNE (Energetic and Relativistic Nuclei and Electron experiment)
  • SWAN (Solar Wind Anisotrophies) - measured Lyman alpha UV light scattered by interplanetary hydrogen atoms.

AKA: Solar and Heliospheric Observatory.
Gross mass: 1,850 kg (4,070 lb).
Height: 3.65 m (11.97 ft).
Span: 9.50 m (31.10 ft).
First Launch: 1995.12.02.
Number: 1 .

More... - Chronology...


Associated Countries
See also
  • Atlas The Atlas rocket, originally developed as America's first ICBM, was the basis for most early American space exploration and was that country's most successful medium-lift commercial launch vehicle. It launched America's first astronaut into orbit; the first generations of spy satellites; the first lunar orbiters and landers; the first probes to Venus, Mars, Mercury, Jupiter, and Saturn; and was America's most successful commercial launcher of communications satellites. Its innovative stage-and-a-half and 'balloon tank' design provided the best dry-mass fraction of any launch vehicle ever built. It was retired in 2004 after 576 launches in a 47-year career. More...

Associated Launch Vehicles
  • Atlas The Atlas rocket, originally developed as America's first ICBM, was the basis for most early American space exploration and was that country's most successful medium-lift commercial launch vehicle. It launched America's first astronaut into orbit; the first generations of spy satellites; the first lunar orbiters and landers; the first probes to Venus, Mars, Mercury, Jupiter, and Saturn; and was America's most successful commercial launcher of communications satellites. Its innovative stage-and-a-half and 'balloon tank' design provided the best dry-mass fraction of any launch vehicle ever built. It was retired in 2004 after 576 launches in a 47-year career. More...
  • Atlas IIAS American orbital launch vehicle. The Atlas II booster was 2.7-meters longer than the Atlas I and included uprated Rocketdyne MA-5A engines. The Atlas I vernier engines were replaced with a hydrazine roll control system. The Centaur stage was stretched 0.9-meters compared to the Centaur I stage. Fixed foam insulation replaced Atlas I's jettisonable insulation panels. Higher performance RL10A-4 or RL10A-4-1 engines replaced Atlas II's RL10A-3-3A. The Atlas IIAS model added four Thiokol Castor IVA solid rocket boosters (SRBs) to the core Atlas stage to augment thrust for the first two minutes of flight. More...

Associated Manufacturers and Agencies
  • NASA American agency overseeing development of rockets and spacecraft. National Aeronautics and Space Administration, USA, USA. More...
  • ESA European agency overseeing development of rockets and spacecraft. European Space Agency, Europe. More...

Bibliography
  • McDowell, Jonathan, Jonathan's Space Home Page (launch records), Harvard University, 1997-present. Web Address when accessed: here.
  • JPL Mission and Spacecraft Library, Jet Propulsion Laboratory, 1997. Web Address when accessed: here.
  • Lockheed Martin Coporation, Atlas Family Fact Sheets, September 1998.. Web Address when accessed: here.
  • NASA Report, SOHO Fact Sheet, Web Address when accessed: here.

Associated Launch Sites
  • Cape Canaveral America's largest launch center, used for all manned launches. Today only six of the 40 launch complexes built here remain in use. Located at or near Cape Canaveral are the Kennedy Space Center on Merritt Island, used by NASA for Saturn V and Space Shuttle launches; Patrick AFB on Cape Canaveral itself, operated the US Department of Defense and handling most other launches; the commercial Spaceport Florida; the air-launched launch vehicle and missile Drop Zone off Mayport, Florida, located at 29.00 N 79.00 W, and an offshore submarine-launched ballistic missile launch area. All of these take advantage of the extensive down-range tracking facilities that once extended from the Cape, through the Caribbean, South Atlantic, and to South Africa and the Indian Ocean. More...
  • Cape Canaveral LC36B Atlas V, Atlas launch complex. Atlas Centaur launch pad, in service from 1964 until the retirement of the launch vehicle. More...

SOHO Chronology


1995 December 2 - . 08:08 GMT - . Launch Site: Cape Canaveral. Launch Complex: Cape Canaveral LC36B. LV Family: Atlas. Launch Vehicle: Atlas IIAS. LV Configuration: Atlas IIAS AC-121.
  • SOHO - . Mass: 1,850 kg (4,070 lb). Nation: Europe. Agency: ESA. Class: Astronomy. Type: X-ray astronomy satellite. Spacecraft: SOHO. USAF Sat Cat: 23726 . COSPAR: 1995-065A. Apogee: 671,400 km (417,100 mi). Perigee: 8,973 km (5,575 mi). Inclination: 29.6000 deg. Period: 29,196.30 min. Summary: Solar and Heliospheric Observatory; orbiting at L1 Lagrange point; solar physics. En route Earth-Sun L1 point Earth-Sun L1 libration point transfer trajectory. Inertial trajectory option..

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