ESA issues so-called Announcements of Opportunity at regular intervals. These are the official access route for institutional users to the utilisation of the various research facilities which are managed by ESA's Directorate of Human Spaceflight.
Announcements of Opportunity are issued for each utilisation discipline: physical sciences, life sciences, technology, Earth observation and space science.
Currently open announcements (if applicable) can be found here.
The Continuously Open Research Announcement is a 'fast-track' approach which may be followed for specific categories of research.
Previously organised Announcements of Opportunity are available in the Research announcement archive.
Some announcements are internationally coordinated with other ISS partners. This is for example the case in specific areas of life and physical sciences.
The International Announcements of Opportunity allow for a worldwide scientific competition and cooperation, by forming the best scientific teams, as well as offering access to an instrument pool from all ISS partners, whereas the European dedicated announcements refer to pre-competitive application areas frequently involving European industries.