Solar and Heliospheric Observatory (SOHO) (1995)

SOHO is the most comprehensive space mission ever devoted to the study of the Sun and its nearby cosmic environment known as the heliosphere. It was launched in December 1995 and is currently funded at least through the end of 2016. SOHO’s 12 instruments observe and measure structures and processes occurring inside as well as outside the Sun and which reach well beyond Earth’s orbit into the heliosphere. While designed to study the “quiet” Sun, the new capabilities and combination of several SOHO instruments have revolutionized space weather research. This article gives a brief mission overview, summarizes selected highlight results, and describes SOHO’s contributions to space weather research. These include cotemporaneous EUV imaging of activity in the Sun’s corona and white-light imaging of coronal mass ejections in the extended corona, magnetometry in the Sun’s atmosphere, imaging of far-side activity, measurements to predict solar proton storms, and monitoring solar wind plasma at the L1 Lagrangian point, 1.5 million kilometers upstream of Earth.