Since the launch of Helios 1A in 1995, France has developed a series of military Earth observation programs. Due to the limited lifetime of satellites, a program was launched to replace the currently operational Helios 2 satellites. This program started as a French contribution to the larger pan-European MUSIS program, and eventually became a mostly French program.^[1] An agreement between France and Germany was reached in April 2015, under which Germany contributes €200 million to building a third satellite, and in exchange receives access rights to the imagery.^[2][3] Sweden and Belgium are also a program partners, which enables the use of a polar ground station.^[4][5]

Unlike the Helios satellites, which used the same bus as the Spot satellites, CSO uses technology derived from the Pléiades satellites. It is much heavier than Pléiades with a mass of 3650 kg.^[6] They are made out of 3 identical satellites. The first one was launched in December 2018, and provide Very High Resolution imagery - like the Helios 2 satellites,^[7] so around 35 cm ^[8] from an 800 km orbit.^[9] The second satellite provides Extremely High Resolution imagery - around 20 cm - from a 480 km orbit.^[6] The third satellite will be launched in 2023 and provide increased revisit capabilities.^[10][11] The satellites have the ability to take infrared images.^[12] The satellite manufacturing was awarded to Airbus Defence and Space, while the optical payload is built by Thales Alenia Space.^[13]

The CSO system is able to produce at least 280 images a day on average.^[4][14]

The program cost is estimated at €1.3 billion,^[1] with an additional €300 million for the ground segment and 10 years of operations.^[15] The marginal cost of the third satellite is €300 million.^[2]