SOHO Spacecraft
http://sohowww.nascom.nasa.gov/about/about.html
SOHO, the Solar & Heliospheric Observatory, is a collaboration between ESA
and NASA to study the Sun, from deep core to the outer corona, and solar
particle wind.
SOHO was launched by an Atlas II-AS (AC-121) from Cape Canaveral Air Station
on December 2, 1995, at 08:08 UT.
SOHO orbits the Sun with the Earth, slowly looping around the First
Lagrangian Point (L1). At L1, the combined gravity of the Earth and Sun
balance, keeping the spacecraft on an Earth-Sun line. L1 is approximately
1.5 million km from Earth in the direction of the Sun (about four times
the distance of the Moon). SOHO therefore has a continuous view of the Sun.
An unexpected loss of contact with SOHO occurred on 25 June 1998. The mission
was recovered and normal operations resumed in mid-November 1998. Despite
subsequent failures of all three gyroscopes (the last in December 1998),
new gyro-less control software installed by February 1999, allowing SOHO to
resume normal operations (and making SOHO the first 3-axis-stabilised
spacecraft to operate without a gyroscope).
MISSION ACCOMPLISHMENTS:
- Provided the first images of structures and flows below the Sun's surface and of activity on the far side
- Revealed the Sun's extremely dynamic atmosphere
- Provided evidence for the transfer of magnetic energy from the surface to the outer solar atmosphere, the corona, through a "magnetic carpet"
- Identified the source regions of the fast solar wind
- New understanding of solar-terrestrial interactions and dramatic improvement of space weather-forecasting based on its continuous stream of images covering the atmosphere, extended corona, and far side
- Findings are in over 2500 papers in refereed journals since launch, representing the work of over 2300 individual scientists.
- Discovery of over 1100 Sun-grazing comets
- Easily accessible data sets
- Service Module: forms the lower portion of the spacecraft. Provides power, thermal control, pointing, telecommunications, and support for the solar panels.
- Payload Module: above Service Module, housing all scientific instruments.
- Dimensions (height, breadth, width): 4.3 x 2.7 x 3.7 m
- Width with solar array deployed: 9.5 m
- Total mass at launch: 1850 kg
- Payload: 610 kg
- Telemetry during real-time operation: 200 Kbits/s
- Telemetry during on-board storage mode: 40 Kbits/s
- CDS (Coronal Diagnostic Spectrometer)
- CELIAS (Charge, Element, and Isotope Analysis System)
- COSTEP (Comprehensive Suprathermal and Energetic Particle Analyzer)
- EIT (Extreme ultraviolet Imaging Telescope)
- ERNE (Energetic and Relativistic Nuclei and Electron experiment)
- GOLF (Global Oscillations at Low Frequencies)
- LASCO (Large Angle and Spectrometric Coronagraph)
- MDI (Michelson Doppler Imager)
- SUMER (Solar Ultraviolet Measurements of Emitted Radiation)
- SWAN (Solar Wind Anisotropies)
- UVCS (Ultraviolet Coronagraph Spectrometer)
- VIRGO (Variability of Solar Irradiance and Gravity Oscillations)