Late 1996 saw the launching of the Solar and Heliospheric Observatory (SOHO) satellite, which was built in a collaborative project between the European Space Agency and NASA. SOHO's missions include studying the sun's internal structure and outer atmosphere, and the solar wind. But satellite observations are immensely costly, and satellites have a limited service life and a high risk of failure.
一九九六年底，歐美合作製造的衛星 SOHO 發射，主要任務就是研究太陽內部構造、外層大氣、太陽風，但衛星觀測經費龐大、壽命短、風險大，SOHO 就曾多次故障。