Since the very first Sycom 1, geostationary satellites from 1960s to 1980s are cylindrical with solar cells covering the body of the satellite. Such examples include:

  • GOES 1 to 7
  • AsiaSat 1 and its HS-376 brethren
  • Dongfanghong 2 and its derivatives including Fengyun 2
  • Himawari 1 to 5
  • Meteosat 1 to 11

This design seems to imply that they are spin stabilized. Which is also corroborated by recollection of Hughes employees, that three axis stabilization was impractical in 1958 due to the number of reaction control thrusters needed.

However, at time of the writing, new geostationary satellites rarely use spin stabilization. The successors to many previously mentioned satellites uses three-axis stabilization instead. Such examples include:

  • GOES 8 to 17
  • AsiaSat 3 to 9
  • Dongfanghong 3, Fengyun 3, Fengyun 4
  • Mirai 1 and Himawari 6 to 9

When and why did three-axis stabilization become prominent in geostationary satellites?

  • 2
    $\begingroup$ You now have a very good answer to your "when" question, but not the "why" part. I suggest you edit out the "why" from this question, and then ask the "why" part of the question as a separate question. $\endgroup$ Jan 16 at 20:47
  • $\begingroup$ @DavidHammen The why part I meant to ask what technological advance makes three-axis stabilization viable. In my mind it would be closely related to when. $\endgroup$
    – Mys_721tx
    Jan 16 at 21:25
  • 1
    $\begingroup$ GEO/GSO satellites are large beasts and and are often developed separately as spacecraft/carrier/platform and payload, e.g Dongfanghong-3 is the spacecraft platform for Dongfanghong-3, Beidou and Chang'e-1 and -2. So the answer could be, when everyone has a platform with three-axis stabilization, then three-axis stabilization becomes prominent. $\endgroup$ Jan 17 at 8:49

2 Answers 2


Partial answer:

The Symphonie satellites A and B were the first communications satellites built by France and Germany (and the first to use three-axis stabilization in geostationary orbit with a bipropellant propulsion system) to provide geostationary orbit injection and station-keeping during their operational lifetime

Symphonie-A was launched from the Kennedy Space Center on December 19, 1974.

Due to the successful operation of Symphonie A, January 12, 1975, President Valéry Giscard d'Estaing of France and German Chancellor Helmut Schmidt exchange their New Year greetings live in a videoconference. Symphonie-A is the first geostationary telecommunications satellite built and operated in Europe.

Symphonie-B is launched from the Kennedy Space Center on August 27, 1975.

August 12, 1983: Symphonie-A makes its final manoeuvre to a graveyard orbit, and is de-activated after 8+1⁄2 years of service.

December 19, 1984: Exactly ten years after the launch of Symphonie-A, Symphonie-B is also deactivated and placed in a graveyard orbit after nine years of active service.

New technologies which have been developed for the spacecraft subsystems and equipment which is now space qualified include a biliquid apogee motor and a biliquid hot gas system for orbit corrections.



Technology and control principles established and space proven during more than four years in orbit operation of these spacecraft has been adapted, extended and improved for INTELSAT V Attitude Determination and Control Subsystem design.

The evolution of Three Axis S/C Stabilization technology started with SYMPHONIE led to INTELSAT V.


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3 axis stabilization from Symphonie led to it being used on Intelsat V:

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Since 1967 Three-Axis Control of Communication Satellites has been studied and developed intensively in Germany. The principle of the so called Bias Momentum Stabilization, which uses the gyroscopic stiffness of a fast running Momentum Wheel for yaw and roll control, was operationally applied to these 2 satellites for the first time.

Bias Momentum Stabilization:

The bias momentum method achieves attitude stabilization by attaching a momentum wheel that incorporates an angular momentum inside a satellite.

  • The angular momentum generated by the spinning of the wheel creates a gyroscopic stiffness that provides the stabilizing effect on the satellite attitude. The angular momentum of the momentum wheel also generates torque through gyroscopic coupling perpendicular to the wheel axis. A three-axis stabilization is achieved using these torques.
  • The representative of the bias momentum is the pitch bias momentum method where the spin axis of the momentum wheel points perpendicular to the orbit normal (pitch direction).
  • The satellite pitch error is controlled by changing the wheel speed, and the nutation of roll/yaw is controlled by magnetic torquers. Therefore, the pitch bias momentum method uses one momentum wheel, together with magnetic torquers, to achieve three-axis control.


Partial why:


Spin benefits:

  • With spin stabilization, the entire spacecraft rotates around its own vertical axis, spinning like a top. This keeps the spacecraft's orientation in space under control.

  • The advantage of spin stabilization is that it is a very simple way to keep the spacecraft pointed in a certain direction.

  • The spinning spacecraft resists perturbing forces, which tend to be small in space, just like a gyroscope or a top.

  • Spin-stabilized craft provide a continuous sweeping motion that is desirable for fields and particles instruments, as well as some optical scanning instruments.

  • Propulsion system thrusters are fired only occasionally to make desired changes in spin rate, or in the spin-stabilized attitude, so not as much as fuel has to be carried or is used over its lifetime (which in early craft was small, sometimes just 3 years).

A disadvantage to this type of stabilization is that the satellite cannot use large solar arrays to obtain power from the Sun. Thus, it requires large amounts of battery power.

  • Another disadvantage of spin stabilization is that the instruments or antennas also must perform “despin” maneuvers so that antennas or optical instruments point at their desired targets.

Three-axis stabilization benefits:

With three-axis stabilization, satellites have small spinning wheels, called reaction wheels or momentum wheels, that rotate so as to keep the satellite in the desired orientation in relation to the Earth and the Sun.

  • If satellite sensors detect that the satellite is moving away from the proper orientation, the spinning wheels speed up or slow down to return the satellite to its correct position. Some spacecraft may also use small propulsion-system thrusters to continually nudge the spacecraft back and forth to keep it within a range of allowed positions.

  • An advantage of 3-axis stabilization is that optical instruments and antennas can point at desired targets without having to perform “despin” maneuvers.

Disadvantage of 3-axis stabilization may have to carry out special rotating maneuvers to best utilize their fields and particle instruments.

  • If thrusters are used for routine stabilization, optical observations such as imaging must be designed knowing that the spacecraft is always slowly rocking back and forth, and not always exactly predictably.

  • Reaction wheels provide a much steadier spacecraft from which to make observations, but they add mass to the spacecraft, they have a limited mechanical lifetime, and they require frequent momentum desaturation maneuvers, which can perturb navigation solutions because of accelerations imparted by the use of thrusters.

Additional why:

In general, attitude control concepts have been classified as active, passive, and semi passive procedures.

  • The active approach use energy available on board the satellite. The passive and semi-passive systems, on the other hand, exploit the environmental forces for stabilization and control.
  • Momentum stabilization has a long history in the satellite industry.
  • Early spacecraft relied heavily on pure spin stabilization, and this method continues to be used on many of today’s satellites during the orbital maneuvering stage.
  • The dual-spin system was soon recognized as a superior stabilization concept for communications satellites. The dual-spin concept has been in use since the 1960s.
  • Over the years, spin stabilization systems gradually gave way to momentum-bias spacecraft employing internal momentum wheels.
  • The US Air Force Agena programs were among the first to incorporate momentum wheels. Some of the earliest Agena spacecraft used a constant-rate pitch momentum wheel for gyroscopic stiffness, and an actively controlled roll reaction wheel for nutation damping.
  • Starting in the late 1950s, momentum bias systems have successfully been used for providing three-axis stabilization for nadir pointing satellites without direct yaw sensing. These momentum bias systems have gradually evolved from single axis momentum storage to three-axis momentum storage.
  • Momentum-biased satellites are three-axis-stabilized when the momentum bias provides inertial stability to the wheel axis, which is perpendicular to the orbit plane and the torque capabilities of the wheel about the wheel axis are used to stabilize the attitude of the satellite in the orbit plane.
  • A pitch bias momentum method is another way of stabilizing a satellite attitude in 3-axes. This method enables control in the roll and yaw directions by pointing the rotational axis of the momentum wheel that has angular momentum in the pitch direction of the satellite (perpendicular to orbital plane). Many communication satellites operated in GEO today incorporate this method.


Recent attempt at purely magnetic control rather than momentum or reaction wheels for attitude control.


Another test - If failure of one of the momentum wheel actuators occurs, two momentum wheel actuators can still be used to control the attitude.


Additional pics:

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I worked for Hughes Aircraft back in the 1980s when this transition was underway. Hughes built many (most?) of the geosynchronous communication satellites in those days, and they were all spin-stabilized. That approach has several benefits.

First, the attitude is passively stable because the angular momentum significantly exceeds the environmental torques (mostly pressure from solar photons at geosynchronous altitude). Three-axis systems are actively stabilized and require reliable operation of the computer, software, reaction wheels, gyro, and attitude sensors. Back then, that was a challenge. Later, larger dual-spin satellites did need active nutation control, but the hardware was much simpler than that of three-axis systems.

Second, spinner thermal design is simpler. The spinning portions alternate between sunlight and darkness on a timescale of a few seconds (most Hughes spinners spun at 30 to 60 RPM). That spread out the solar heating on the body.

Ultimately, spin stabilized designs could not generate enough power as communications payloads became more ambitious and power-hungry. Geosynchronous communication satellites these days can require over 10 kW of solar array power. Spacecraft solar arrays cost on the order of 1M USD per kilowatt, way more than the ones used on houses (because they use very advanced cell technology with little market demand to drive down prices). A three axis spacecraft mounts the cells on a flat panel and then points rotates the panel to face the Sun more or less full on. A spinner, on the other hand, places the arrays on a cylinder which is only partially illuminated. In fact, you need roughly pi times more solar array area to get the same output as from a flat array. That means you start out with a cost disadvantage of about 20M USD, which is too much in the competitive market. In addition, there are practical limits to how large a cylinder you can launch. Intelsat VI (which I worked on) is close to the max allowed by rocket fairing sizes. Making the cylinder longer was tried as well (on Intelsat VI and others) by deploying a lower cylinder (like a skirt). It worked, but it more or less reached its limits with spacecraft like Intelsat VI.

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The early weather satellites were also spin stabilized, and they used the spin to scan the Earth's disc. They worked, but improved performance called for instruments that work more like cameras, and clearly a spinning platform would not work for them. Hence all newer weather satellites use very sophisticated three axis systems to provide an exceptionally steady platform.

Acknowledging the inevitable, Hughes designed and built its first three axis geosynchronous communications satellites in the late 1980s and early 1990s. Since then, almost all geosynchronous satellites have been three axis stabilized.

Image from https://twitter.com/y00st/status/843584490220011520


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