The COESO (Collaborative Engagement on Societal Issues) project facilitates and supports participatory research in SSH, through a service-first approach. COESO supports ten Citizen Science pilots presenting a variety of disciplines, societal challenges and types of engagement with citizens in different European countries. COESO project will specifically support collaborative practices in Citizen Science by developing a Virtual Ecosystem for Research Activation (VERA), a platform envisioned as a "collaboratory” providing a set of tools to discover potential partners, to define and co-design the activities, to co-create new knowledge and solutions, and to deliver them to society. COESO will furthermore collaborate with research funding organizations to enhance financial support to Citizen Science projects in the SSH and explore the frontiers of innovation in SSH public engagement by achieving a complete mutual learning with the teams involved in the Pilots. Finally, “Cooperation analytics” will be designed to measure the quality of collaboration between researchers and citizens in VERA. Those analytics will be useful to the project teams themselves but they will also be a major contribution to funders, policy makers, research organizations and other stakeholders supporting Citizen Science policies. COESO’s overall objective is to overcome the obstacles that hinder the development of Citizen Science in the SSH. COESO will enable a dramatic growth of Citizen Science projects in these disciplines and will intensify the collaborations between SSH researchers and citizens to tackle together the many societal challenges European societies face today. VERA will be one of the core services offered by OPERAS Research Infrastructure to the scientific community.