Composante Optique Spatiale
Mission typeMilitary reconnaissance
OperatorCNES / DGA
COSPAR ID2018-106A (CSO-1)
2020-104A (CSO-2)
SATCAT no.43866 (CSO-1)
47305 (CSO-2)
Mission duration10 years (planned)
Spacecraft properties
ManufacturerAirbus Defence and Space (satellite)
Thales Alenia Space
(optical payload)
Launch mass3,655 kg (8,058 lb) (CSO-1)
3,652 kg (8,051 lb) (CSO-2)
Start of mission
Launch date19 December 2018,
13:37:00 UTC (CSO-1)
29 December 2020,
16:42:07 UTC (CSO-2)
2023 (planned) (CSO-3)
RocketSoyuz ST-A (CSO-1, CSO-2)
Ariane 62 (CSO-3)
Launch siteCentre Spatial Guyanais, ELS and ELA-4
ContractorProgress Rocket Space Centre, Arianespace
Orbital parameters
Reference systemGeocentric orbit
RegimeSun-synchronous orbit
Altitude800 km (500 mi) (CSO-1)
480 km (300 mi) (CSO-2)

Composante Spatiale Optique (CSO; English: Optical Space Component) is a French military Earth observation satellite program of third generation. It replaces the Helios 2 satellites. It is sometimes referred to as the MUltinational Space-based Imaging System for Surveillance, Reconnaissance and Observation (MUSIS program).

Program history

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]

Technical capabilities

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]


  1. ^ a b (in French)[1] French Finance Law for 2013 : Defence : Equipment
  2. ^ a b (in French) [2] article
  3. ^ [3] SpaceNews article
  4. ^ a b (in French) [4] Hearing of the French Space Command Chief by the National Assembly
  5. ^ "CSO-1 L'ESPACE AU SERVICE DE LA DÉFENSE". CNES. 7 February 2019. Retrieved 11 October 2020.(in French)
  6. ^ a b [5] page on CSO on the CNES website
  7. ^ (in French) [6] Hearing on the Director of Military Intelligence at the French National Assembly
  8. ^ [7] SpaceNews article on Helios II B
  9. ^ (in French) [8] French Military Planning Law for 2014-2019
  10. ^ Lagneau, Laurent (4 March 2022). "Faute de lanceur Soyouz, la mise sur orbite du satellite militaire français CSO-3 sera retardée d'un an" [In the absence of a Soyuz launcher, the orbital insertion of the French military satellite CSO-3 will be delayed by a year]. Opex360 (in French). Retrieved 7 March 2022.
  11. ^ (in French) [9] Article on Musis on the French Ministry of Defense website
  12. ^ [10] Sofradir wins military satellite IR detector contract
  13. ^ "Lancement de la réalisation des satellites CSO du programme Musis". Direction générale de l'armement. 28 June 2010. Retrieved 13 November 2013.(in French)
  14. ^ (in French) [11] Article mentioning Pléiades programming rights
  15. ^ (in French) [12] Press release from the DGA