Paris and Berlin have agreed to launch a future addition to the Composante Spatiale Optique (CSO) high-resolution military reconnaissance satellite network on Ariane 6. The satellite, CSO 3, is scheduled to enter service in 2021 to improve revisit times offered by the first two platforms.

The decision was welcomed in France, in view of Germany's past launcher choices for its military satellites. In 2013, Berlin selected the Falcon 9 to launch its Sarah 2 and 3 radar satellites — the first time SpaceX had signed a contract with a European government customer.

The CSO programme was launched by French space agency CNES in 2010 to provide follow-on satellites for Helios 2A and 2B from 2018 onwards as part of the Multinational Space-Based Imaging System (MUSIS) programme.

Airbus Defence and Space was awarded a €795m contract to build the first two CSO platforms (offering resolutions of around 35 and 20cm), with an option for a third satellite. The optical payload is provided by Thales Alenia Space. Germay joined the programme in 2015, contributing €210m in funding for the third satellite.

Sweden is also a partner on the programme, allowing for the installation of a dedicated ground station north of the Arctic Circle.

The CSO satellites are based on the AstroSat 1000 platform used on the Pléiades satellites. They have a lift-off mass of around 3.5t and will operate from sun-synchronous orbit at two different altitudes (480 and 800km) with a service life of at least 10 years.