CSO 2 | Soyuz STA/Fregat

Featured image provided by: AFP 2020 / Jody AMIET

Launch Window/Lift Off Time
(Subject to change)
NET December 29, 2020 – 16:42:07 UTC | 13:42:07 Kouru Time
Mission Name
Launch Provider
(What rocket company launched it?)
(Who’s paid for this?)
French CNES Space Agency
Soyuz STA
Launch Location
Soyuz Launch Complex, Kourou, French Guiana
Payload mass
3,562 kg (~7,853 lbs)
Where did the satellites go?
Sun-Synchronous (SSO) orbit of 480 km (300 miles)
Did they attempt to recover the first stage?
No, this is not a capability of Arianespace.
Where did the first stage land?
It crashed into the Atlantic Ocean.
Did they be attempt to recover the fairings?
No, this is not a capability of Arianespace.
Were these fairings new?
How was the weather?
This was the:
– Last launch of 2020!
– 5th launch of a Soyuz medium launcher in 2020
– 10th launch for Arianespace in 2020
Where to watch
Official livestream

How did it go?

On December 29, 2020 at 16:42:07 UTC, for the final launch of the year, Arianespace successfully launched the CSO 2 satellite to its designated orbit. The flight went off without a hitch and the timeline was followed to near perfection. The next planned launch of a CSO satellite will be in 2022.

What is the CSO 2 satellite?

The second satellite of the CSO constellation aims to study the Earth, specifically for the purpose of defense and security. This second satellite will be in charge of identifying different elements while the other two satellites in the constellation will be in charge of reconnaissance. Each satellite will be deployed into various polar orbits. CSO 2 will be deployed into a 480 km (about 300 mile) polar orbit.

An artists rendering of a CSO satellite. (Credit: Arianespace)

Satellite History

CSO 1, the first satellite of the constellation, was originally launched in December of 2018, with the help of Arianespace. Previously, the French along with Belgium, Spain, and Greece had been using the Helios 2 system for their military Earth observations. Since these satellites, launched in 1995, don’t have incredibly long lifetimes (about 10 years) they have to be replaced with a different system. In this case, it is the CSO program. Some of the patterns of the this program include Germany, which will invest 200 million euros into CSO 3 which will in turn give them imagery rights. Sweden and Belgium are incorporated to enable the use of polar ground stations to control and operate the satellites from. Satellite manufacturing was given the Airbus Defense and Space while the optical elements are constructed by Thales Alenia Space.


Each of the three satellites will have identical designs and very similar functions. All satellites will be able to take very high resolution images in the visible and infrared bands. Due to this, they will be able to get all the images they need at all hours of the day from nearly any location on Earth. This can also help in areas of crisis, where real-time images can be obtained and assist in many ways. Each CSO satellite has a planned minimum lifetime of 10 years. Due to the classified nature of these satellites, no more information could be obtained.

What rocket is it launching on?

Introduced in 1966, the Soyuz rocket (also known as R7) has been the workhorse of the Soviet/Russian space program. The first launch of the Soyuz 2.1a version on November 8, 2004 from the Plesetsk Cosmodrome represented a major step in the Soyuz launch vehicle’s development program. Fregat is the upper (4th) stage of Soyuz 2.1/ST, and it first flew in the year 2000.

Evolution of the R7 / Soyuz rocket family (Credit: NASA / Peter Gorin / Emmanuel Dissais)

The Soyuz version currently being used for most satellite launches (as distinct from crewed capsules or cargo capsules to the ISS) is a four-stage launch vehicle, which consists of:

  • four side boosters (booster stage)
  • a central core booster (first stage, which is lit at the same time as the side boosters, on the ground)
  • an upper (central) stage which is common to all Soyuz rockets regardless of payload
  • the re-startable Fregat “upper” stage (fourth stage) – this is not always used, for example it is not used with Soyuz spacecraft or Progress spacecraft


The side boosters’ RD-107A engines are powered by liquid oxygen and kerosene, which are the same propellants used on each of the rocket stages. The kerosene tanks are located in the cylindrical part and the liquid oxygen tanks in the conical section. Each engine has four combustion chambers and four nozzles.

During side booster separation, the boosters perform a well-known pattern, in which they peel off and cartwheel outwards! This is known as the “Korolev cross,” which is named after Sergei Korolev, the Chief Design Engineer of the USSR space program in the 1960s.

Korolev cross during side booster stage separation on a Soyuz launch
“Korolev cross” seen during side booster stage separation on a Soyuz launch.


The center core is fitted with an RD-108A engine, and also has four combustion chambers and four nozzles. It also has four Vernier thrusters, used for three-axis flight control once the side boosters have separated. The third stage engine’s thrust enables the stage to separate directly from the central core. This is called “hot staging.”


The third stage uses either an RD-0110 engine in the Soyuz ST-A (2.1a) version or an RD-0124 engine in the ST-B (2.1b) version. This flight is using a 2.1b vehicle, so in this case, the stage has an RD-0124 engine.

RD-0124 motor at Salon-du-Bourget 2013. (Credit: Pline)


Flight qualified in 2000, the Fregat upper stage is an autonomous and flexible stage that is designed to operate as an orbital vehicle. It extends the Soyuz launcher’s capability, now covering a full range of orbits (LEO, SSO, MEO, GTO, GEO and Earth escape). Fregat is independent of all the other stages, as it has its own guidance, navigation, attitude control, tracking, and telemetry systems. The engine burns storable propellants – UDMH (unsymmetrical dimethylhydrazine) and NTO (nitrogen tetroxide) – and can be restarted up to 50 times in flight so that it can carry out very complex missions.

The Fregat upper stage is encapsulated in a fairing with the payload and a payload adaptor/dispenser. It is entirely independent from the rest of the rocket, having its own systems on board for guidance, navigation and control. It also provides its own telemetry data back to the ground.

Fregat uses the S5.92 engine, which uses unsymmetrical dimethyl hydrazine (UDMH) for fuel and nitrogen tetroxide (NO4) for oxidizer. The propellent is hypergolic, which means they combust on contact. The fuel and oxidizer will combust as soon as they meet in the combustion chamber.


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