SOHO (SOlar Heliospheric Observatory) is a space-based observatory, viewing and investigating the Sun from its deep core, through its outer atmosphere - the corona - and the domain of the solar wind, out to a distance ten times beyond the Earth's orbit. SOHO is designed to study the internal structure of the Sun, its extensive outer atmosphere and the origin of the solar wind, the stream of highly ionized gas that blows continuously outward through the Solar System. This space-based Observatory is viewing the Sun from its deep core, through its outer atmosphere - the 'corona' - and the domain of the solar wind, out to a distance ten times beyond the Earth's orbit