Satellite 3-Axis control

With GEO Satellite control it is important to know the definition of the 3-Axis being controlled. Typically the Axis is referenced from the CM (Center of Mass) or CG (Center of Gravity) of the satellite  to the orbit plain.  Normally the X-Axis points East and West. The Y-Axis points North and South. And the  Z-Axis points at the Earth and away from the Earth. Sensors are located on the spacecraft and aligned to produce positive and negative error signals in each axis for use by the Attitude Control System (ACS). This drawing depicts a typical satellite’s X,Y and Z axis.

Movement around the Z-Axis is Yaw

In 3-Axis satellite control movement around the Z-Axis is called Yaw. Errors in this Axis will shift the pointing of the communications transmit pattern of the satellite in what appears to be a clockwise/counterclockwise movement on the earth. Through the normal progression of an orbit Yaw will translate to Roll in a quarter of the orbit.  Both errors can be managed by active control and typically Roll control is chosen to be controlled if only one of the two Axis is to be controlled. The diagram and animation show a visual representation of this movement.

Movement around the Y-Axis is Pitch

In 3-Axis satellite control movement around the Y-Axis is called Pitch.  Errors in this Axis will shift the pointing of the communications transmit pattern of the satellite in what appears to be an east/west movement on the earth. The diagram and animation show a visual representation of this movement.

Movement around the X-Axis is Roll

In 3-Axis satellite control movement around the X-Axis is called Roll.  Errors in this Axis will shift the pointing of the communications transmit pattern of the satellite in what appears to be a north/south movement on the earth.  Through the normal progression of an orbit Roll will translate to Yaw in a quarter of the orbit.  Both errors can be managed by active control and typically Roll control is chosen to be controlled if only one of the two Axis is to be controlled.  The diagram and animation show a visual representation of this movement.

Reason for Seasons

The Earth’s pole is offset by 23.45 degrees, as it orbits the Sun it appears to precess above and below the equator.Earth's Seasons

Orion GEO

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INFORMATION

Shining light on satellites and how they operate. Drawing from over 30 years of knowledge and experience in all phases of the life of a satellite from concept, to operations, and through end of life. You will find short topics intended to give you an understanding of how they work, the general concepts, and principals used along with information on ground systems. There is also a section dedicated to topics that can be used as basic concept training along with links to animations and 3D models I have created.