Helios

Helios-A, -B, Helios-1, -2

Mission Profile

Helios (Helios-A and Helios-B) were two identical West German/NASA spacecraft launched in December 1974 and January 1976 aboard Titan IIIE/Centaur rockets on a collaborative mission to study the inner heliosphere closer to the Sun than any previous spacecraft. At perihelion Helios-A reached 0.31 AU from the Sun and Helios-B reached a record 0.29 AU — records that stood for over four decades until Parker Solar Probe surpassed them in 2018. The spacecraft measured solar wind plasma, magnetic fields, cosmic dust, and energetic particles in the never-before-explored inner heliosphere, revealing that the solar wind accelerates rapidly close to the Sun. Both spacecraft continue to orbit the Sun in silence, their nuclear power sources exhausted, as relics of the pioneering era of solar physics research.