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.
3 axis stabilization from Symphonie led to it being used on Intelsat V:
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
- 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.
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.
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.
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
- Early spacecraft relied heavily on pure
spin stabilization, and this method continues to be used
on many of today’s satellites during the orbital
- 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
- 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
- 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
- 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.