ESA Science & Technology - News Update - Assessment Phase

The BepiColombo mission to Mercury which includes two orbiting spacecraft. The Solar Orbiter mission, which will permit close-up and high-latitude studies of the Sun.

By grouping such missions, mission costs may be minimised while still maximising the overall scientific return. This is achieved by introducing a high degree of commonality within a mission group in terms of: reuse of platforms and equipment, engineering approaches, project teams management, launcher procurement and operations, etc.

At its meeting on 8 June 2004, the SPC re-confirmed Solar Orbiter as an integral part of the Cosmic Vision Programme 2003-2013, with a target launch date in October 2013 (and no later than May 2015). Furthermore, the SPC stressed the importance of maintaining a close technological synergy between Solar Orbiter and BepiColombo.

In 2004 the ESTEC SCI-AM section, in collaboration with the Study Scientist, is responsible for the Assessment Phase of the Solar Orbiter. The remainder of this note provides an overview of these activities.

Since the original Concurrent Design Facility (CDF) study of Solar Orbiter carried out in 1999, major progress on the definition of the BepiColombo mission has been achieved. Therefore in Spring 2004, a second CDF study was performed. The original CDF run investigated a so-called "single ship" design, comprising a single spacecraft with integrated Solar Electric Propulsion (SEP) units. The cruise phase solar arrays that powered the SEP were to be jettisoned at the end of the cruise. The second CDF run investigated a "composite" design, where the orbiter spacecraft including the payload would be connected to a separate Solar Electric Propulsion Module (SEPM), which would be jettisoned in its entirety after the cruise phase. The SEPM would be a replicate of the SEPM for BepiColombo, with the potential for significant cost savings. The CDF study report of April 2004 demonstrated that the composite approach seemed feasible.

In parallel to the CDF study, a payload study by an industrial team has also made good progress. A critical analysis of the anticipated payload was made, in particular to check that the science requirements would be met, and that the payload mass and power resources were within allocations. The Payload Working Groups assisted in this exercise, and a combined effort will result in a revised Payload Definition Document to be released in the summer.

The third major exercise commenced in early May 2004, with the kick off of two independent and competitive industrial studies. These studies are organised into two phases:

• Phase one will investigate the mission scenarios, and evaluate the current baseline, using a direct injection and solar electric propulsion, against alternative methods of achieving the important operation orbit around the Sun. The major constraints are mass, cost and the extreme thermal environment.
• Phase two will provide a detailed analysis of the mission, and spacecraft on the selected mission profile from phase one. In addition the payload integration study will have been completed, providing an updated reference for the payload.

Upon the completion of phase two (December 2004), SCI-AM will produce a final report summarising the two industrial approaches and making recommendations as to how to proceed into the next phase of Solar Orbiter development. The completion of the assessment activities is presently planned for March 2005.