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Policy for Missions of Opportunity in the ESA Science Directorate

Missions of Opportunity are long-established, important building blocks within ESA's Science Programme. The definition and prerequisites for Missions of Opportunity are summarised in this article, and guidelines are provided on how the scientific community can access this important Programme element.

The ESA Science Programme provides Europe with the tools to be a world leader in space science. For the scientific community, the Programme fosters the conditions to sustain and enhance excellence, leading to discoveries and innovation.

The Science Programme is populated by different types of missions, each of which fulfil a clearly defined role:

Large (L-class) missions are European-led flagship missions with a launch cadence of approximately one every decade. JUICE (L1), Athena (L2), and LISA (L3) have been selected within this category.

Medium (M-class) missions may be ESA-led or carried out with international partners. These provide flexibility within the programme and have an expected launch cadence of two per decade. Current M missions are: Solar Orbiter (M1), Euclid (M2), and PLATO (M3).

Small (S-class) missions are a relatively new concept that allow Member State agencies to play a leading role in missions. The first S-class mission is CHEOPS.

Missions of Opportunity in the ESA Science Programme

While the L, M, and S missions provide a framework for medium to long-term planning, Missions of Opportunity provide an important element of flexibility, allowing ESA and the community to respond quickly to opportunities that arise to participate in missions from partner agencies.

The spirit of a Mission of Opportunity is to provide a tool through which the Programme can implement a relatively small, non-enabling participation in a partner-led mission, in exchange for a clear opportunity for the broad space science community in Europe to access scientific opportunities (for example, access to data or participation in mission science teams) that would otherwise not be available to them.

Missions of Opportunity, which have long been part of the Science Programme, have consistently demonstrated their importance as a building block of the Programme by providing valuable, high-profile opportunities to the science community. The current portfolio of Missions of Opportunity consists of contributions to Hinode, IRIS, Microscope, PROBA-2, PROBA-3, XARM, and ExoMars.

Prerequisites for Missions of Opportunity

Only missions that have been fully approved by the partner agency can be eligible for a Mission of Opportunity proposal in the Science Programme.

A dedicated budget planning corridor, of approximately three per cent of the Science Programme's income, exists for Missions of Opportunity. This amount represents an average, long-term value, as the year-on-year spending profiles may differ for different missions. Irrespective of the spending profile, the total cost of a Mission of Opportunity is capped at 50 Million Euros.

Contributions for a Mission of Opportunity may vary in nature but they must be a concrete, well-defined contribution to the mission’s implementation. Examples of contributions to previous Missions of Opportunity include the provision of hardware items (representing European excellence or unique European technology), or support to operations (including use of the ground station network or support to a mission's scientific operations). Scientific data analysis and exploitation cannot be part of a Mission of Opportunity.

Participation in a Mission of Opportunity must result in a clearly defined scientific return for scientists in ESA Member States, in terms of access to scientific data or participation in the mission in a manner that would otherwise have been inaccessible to them.

Any contribution to a Mission of Opportunity should be on a non-exchange of funds basis.

The path to approval for a Mission of Opportunity

Opportunities to participate in a Mission of Opportunity can be brought to the attention of the ESA Science Directorate Executive by potential partners or by Member State Delegations. Proposals for Missions of Opportunity cannot be submitted directly by the scientific community, but individual scientists may bring to the attention of the Executive a possible cooperation opportunity, in which case the Executive will explore the nature and possible interest of such an opportunity.

If the Executive consider that the opportunity satisfies the criteria of being realistic, of potential interest, consistent with the Science Programme strategy, and conforming to the rules for Missions of Opportunity, the Executive will consult with the Science Programme Committee (SPC). If considered appropriate, and on the basis of this non-binding consultation, the Executive would proceed to negotiate possible terms for the opportunity with the potential partner and define the content of a proposal to be presented to the SPC. Should time be of the essence (for example, because the opportunity presents itself in a narrow window), and the non-binding consultation be unfeasible given the schedule of SPC meetings, the Executive would consult the SPC Chair on the way to proceed.

After this preparatory phase, should a proposal for a Mission of Opportunity in the Science Programme have to be considered, the Advisory Structure of the Science Directorate (the Space Science Advisory Committee, with the support of the Astronomy Working Group and of the Solar System and Exploration Working Group) will, as is customary, be asked for a recommendation for any proposal prior to it being put forward to the SPC. In particular, they will be asked to assess the mission's intrinsic scientific value and interest, as well as the adequacy of the proposed scientific quid pro quo. The scientific case will have to be argued, in front of the relevant Working Group, by the potential partner (or by a scientist designated by the potential partner); the Working Groups' scientific assessment will, as customary, be used in support of the recommendation of the Space Science Advisory Committee.

A proposal to SPC for participation in a Mission of Opportunity would consist of a proposal from the Executive outlining the terms of the participation, and a presentation of the science case for the mission, provided by the partner agency. If the proposal is approved by the SPC the implementation of the Mission of Opportunity will proceed as for any other Programme element.

Access to Missions of Opportunity

The opportunity to participate in the exploitation of the scientific return of a Mission of Opportunity will be made available to scientists in ESA Member States. Therefore, once approved by the SPC the details of the Mission of Opportunity will be advertised by ESA. Participation will be open to the European space science community following Announcements of Opportunity, and the beneficiaries will be selected on a competitive basis.

For further details, please contact:
Luigi Colangeli
Head of the Science Coordination Office
Directorate of Science
European Space Agency

Last Update: 12 February 2018

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