SOHO Satellite

The Solar and Heliospheric Observatory (SOHO) satellite has provided the most detailed picture to date of the nature of the solar wind. Hydrogen and helium make up 99.9 percent of the wind, but the sensitive mass spectrometer aboard SOHO can make measurements of the trace constituents. A group of instruments aboard are collectively called the Charge, Element, and Isotope Analysis System (CELIAS). They have detected isotopes of silicon, sulfur, calcium,shromium, iron and nickel in the solar wind. They also detected isotopes of neon and argon which had not been detected by earlier satellites, but had been observed from the moon twenty years before during the Apollo lunar landings.

The isotopes provide clues about where the solar wind originates in the dynamic structure of the sun. They can help model the transfer mechanisms from the sun's surface into the corona.