SOHO was launched into its three-month journey to Lagrangian point No.1 on December 2nd, 1995, from Cape Canaveral by an Atlas-IIAS launcher. The whole mass of the spacecraft when launched was 1610 kg plus 240 kg propellant which is sufficent for at least six years of operation.
When orbiting L1 between the Earth and the Sun the spacecraft can enjoy an uninterrupted view of the Sun, the heliosphere, and the solar wind particles. One L1 orbit takes about 6 months.