正 The European Space Agency (ESA) launched its science programme Horizon 2000 in themid eighties.this programme encompasses four big missions, the cornerstones,in addition tosmaller missions. The four cornerstones are:SOHO/Cluster a solary observatory and in situmeasurements of the Earth magnetosphere,XMM and X-ray observatory,Rosetta a comet ren-dezvous mission,and FIRST a far infrared observatory.SOHO was successfully launched in
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