Astronomy is developing with the combination of data provided by space platforms and ground based observatories, across the electromagnetic spectrum as well as, more recently, by means of high-energy particles and gravitational waves. The current development of large ground-based observatories and more complex space missions, requires considering the benefits of their complementarity for the sake of science excellence.

For this purpose, it is important to review the synergies and the need for cooperation, as it is the case in the new multi-messenger astronomy, but also to identify the challenges to advance further and how to mitigate potential difficulties. Examples of the challenges to be addressed includes, exchange of information, coordination of mutual support, open data access, response to alerts, time allocation or the evaluation of joint proposals.

On the other hand, facilities in space are currently large and expensive, but also the new ground-based large facilities demand important public resources. The identification of the big scientific questions and how they can be better addressed, should thus involve both space and ground-based projects in their roadmaps. The discussion of new elements and the establishment of long-term plans have to be formulated taking into account the full exploitation of both, showing to decision-makers and efficient use of the funding.

The purpose of this Forum is to share ideas among a number of experts to facilitate and encourage coordination in the preparation of astronomy roadmaps and looking for collaboration opportunities in the development, operation and data exploitation of the different, ground and space based, observatories. Particular attention will be devoted to the identification of difficulties in the development of joint activities and how they could be addressed by individual astronomers, national agencies or international entities.