Composante Spatiale Optique

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Composante Optique Spatiale
Mission typeMilitary reconnaissance
Earth observation
OperatorFrench Armed Forces
Mission duration12 years
Spacecraft properties
ManufacturerThales Alenia Space · Airbus Defence and Space
Launch mass3,500 kg (7,700 lb)
Start of mission
Launch dateCSO-1: 19 December 2018
CSO-2: 2020
CSO-3: 2022
Orbital parameters
Reference systemGeocentric
RegimePolar orbit
Perigee altitude480 km (300 mi)
Apogee altitude800 km (500 mi)

Composante Spatiale Optique (CSO; English: Optical Space Component) is a French military Earth observation satellite program. It will replace the Helios 2 satellites. It is sometimes referred to as the MUSIS program.

Program history[edit]

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 200M€ to building a third satellite, and in exchange receives access rights to the imagery.[2][3] Sweden is also a program partner, which enables the use of a polar ground station.[4]

Technical capabilities[edit]

Unlike the Helios satellites, which used the same bus as the Spot satellites, CSO will use technology derived from the Pleiades agile satellites. It will be much heavier than Pléades with a mass of 3.5t.[5] They will be made out of 3 identical satellites. The first one will be launched in 2018, and will provide Very High Resolution imagery -like the Helios 2[6] satellites, so around 35 cm[7]- from an 800 km orbit.[8] The second one will provide Extremely High Resolution imagery -around 20 cm- from a 480 km orbit.[5] The third one will be launched in 2021 and will provide increased revisit capabilities.[9] The satellites will have the ability to take infrared images.[10] The satellite manufacturing was awarded to Airbus Defence and Space, while the optical payload will be built by Thales Alenia Space.[11]

The CSO system will be able to produce at least 280 images a day on average.[4][12]

The program cost is estimated at 1.3 billion Euros.[1] with an additional 300 million for the ground segment and 12 years of operations.[13] The marginal cost of the third satellite is 300M€.[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. ^ a b [5] page on CSO on the CNES website
  6. ^ (in French)[6] Hearing on the Director of Military Intelligence at the French National Assembly
  7. ^ [7] SpaceNews article on Helios II B
  8. ^ (in French)[8] French Military Planning Law for 2014-2019
  9. ^ (in French)[9] Article on Musis on the French Ministry of Defense website
  10. ^ [10] Sofradir wins military satellite IR detector contract
  11. ^ (in French)"Lancement de la réalisation des satellites CSO du programme Musis". Direction générale de l'armement. 28 June 2010. Retrieved 13 November 2013.
  12. ^ (in French)[11] Article mentioning Pléiades programming rights
  13. ^ (in French)[12] Press release from the DGA