SOHO launch. The launch of the Solar and Heliospheric Observatory (SOHO) spacecraft took place on an Atlas II-AS (AC-121), from Cape Canaveral Air Station, on 2 December 1995, at 03:08 EST (08:08 UTC). SOHO, which became operational in March 1996, has been studying the Sun's surface, atmosphere and solar wind in order to increase our understanding of a variety of solar processes. As of 2010, it is still in operation and mission extensions to December 2012 have been approved.