Iranian Researchers Make Reaction Wheels for Zafar-2 Satellite

Reaction wheels, as one of the most vital satellite subsystems, play a fundamental role in stabilizing, changing, and correcting the satellite's position in the orbit, and four of these modules are typically used in each satellite.

Zafar 2 satellite was designed and built as a sensing satellite with the aim of imaging the Earth's surface and monitoring natural resources. The satellite is equipped with a multispectral (color) imaging payload and is capable of providing valuable data for various scientific and applied fields in Iran.

A reaction wheel (RW) is an electric motor attached to a flywheel, which, when its rotation speed is changed, causes a counter-rotation proportionately through conservation of angular momentum.

A reaction wheel can rotate only around its center of mass; it is not capable of moving from one place to another (translational force).

Reaction wheels are used primarily by spacecraft for three-axis fine attitude control, but can also be used for fast detumbling.

Reaction wheels do not require rockets or external applicators of torque, which reduces the mass fraction needed for fuel. They provide a high pointing accuracy, and are particularly useful when the spacecraft must be rotated by very small amounts, such as keeping a telescope pointed at a star.

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Mohammad Jafari