The assessment study of the Solar Orbiter has addressed all mission areas, from the scientific requirements to the payload complement, the space and ground segments, and the respective technology readiness, including all corresponding programmatic aspects.

Specific attention has been given to the reference payload, in the form of a dedicated industrial study as well as of internal activities, in order to prepare adequately for the future instrument Announcement of Opportunity and maintain a certain degree of control over the corresponding spacecraft resources. These activities have indicated that, given the number and complexity of the instruments on board, such an attention should be also given in the following mission phases. The system level study has indicated that two mission profiles are viable and compatible with the science requirements:

a) Solar Electric Propulsion and a 1.8-year cruise phase (higher development risk/cost);

b) Chemical Propulsion, with a 3.4-year cruise phase (lower development risk/cost).

In both cases, all critical design drivers have been analysed and, while design challenges do exist, no major feasibility questions have been raised, showing a feasible mission, technically compatible even with the launch date of October 2013. On the basis of both programmatic and technical reasons, a launch in May 2015 is baselined.

The industrial study has also confirmed the relevance of the BepiColombo link and of the related TDAs, showing that a very limited number of Solar Orbiter specific TDAs are required. The programmatic analysis has indicated that, under the assumption of a tight resource management and a ‘no-nice-to-have’ approach, the Solar Orbiter mission is compatible with the original budget allocation.