Solar orbiter: A challenging mission design for near-Sun observations

The Sun's atmosphere and heliosphere represent uniquely accessible domains of space, where fundamental physical processes common to solar, astrophysic al and laboratory plasmas can be studied under conditions impossible to dup licate on Earth, and at a level of detail that it is not possible to achiev e at astronomical distances. A Solar Orbiter Mission designed to take the n ext step in our exploration of these domains was the topic of a technical p re-assessment study performed in 1999 within the framework of ESA's Solar P hysics Planning Group. A Solar Orbiter-type mission was also proposed to ES A by an international team of scientists in response to the recent call for mission proposals for two Flexi-missions (F2 and F3). A key feature of the mission is a spacecraft orbit that not only provides m ultiple, near-Sun passes, but which also carries the Orbiter to moderately high solar latitudes. This, together with the cost constraints associated w ith Flexi-type missions, represented a significant challenge in terms of mi ssion and system design.