The book provides a structural analysis of the European space effort from an institute change perspective. It analyzes the EU-ESA inter-institutional relationship, gives an overview of the development of space policy in Europe, and advances the debate about the impact of the European integration process on existing institutional actors. While European Space collaboration was initially developed outside the competences of the European Union (EU) with space programmes being carried out almost exclusively under the framework of European Space Agency (ESA) and national agencies, the EU has gained “shared competences” (Art. 2, TFEU) in space policy following the adoption of the Lisbon Treaty. Currently the EU and ESA work together under a Framework Agreement. In 2016, the EU Commission has published a Communication entitled “European Space Policy” (ESP). Even though ESA’s Member States have agreed to keep ESA as an intergovernmental organisation during the ESA Ministerial Council of 2014, the discussion about ESA becoming part of the EU framework continues. The EU’s ambitions for leadership in European space policy raise question concerning the future of ESA. The study of institutions lies at the heart of political sciences. Strikingly the theoretic framework qualifying institutional change and making it comparable leaves room for more concrete and testable dimensions of institutional change.