The primary function of a spacecraft flight control system is to maintain the spacecraft's attitude and orientation in space. This is achieved through the use of various sensors, actuators, and control algorithms.

Gravity gradient stabilization is not a type of spacecraft attitude control system. It is a passive attitude control technique that uses the gravity gradient between the spacecraft and the Earth to maintain the spacecraft's orientation.

A reaction wheel is a momentum exchange device used to control the spacecraft's attitude. It consists of a spinning flywheel that stores angular momentum. By changing the speed or direction of rotation of the flywheel, the spacecraft's angular momentum can be changed, thus controlling its attitude.

The main difference between an open-loop and a closed-loop spacecraft flight control system is that an open-loop system does not use feedback, while a closed-loop system does. In an open-loop system, the control inputs are determined solely based on the desired output, without taking into account the actual output. In a closed-loop system, the control inputs are adjusted based on the difference between the desired output and the actual output.

A Kalman filter is an algorithm used to estimate the state of a dynamic system, such as a spacecraft, from a series of noisy measurements. The Kalman filter combines the measurements with a mathematical model of the system to produce an estimate of the system's state that is more accurate than either the measurements or the model alone.

Attitude acquisition is the process of bringing a spacecraft into a desired attitude. This is typically done using a combination of attitude sensors and actuators.

Attitude control is the process of maintaining a spacecraft's attitude once it has been acquired. This is typically done using a combination of attitude sensors and actuators.

Attitude determination is the process of determining a spacecraft's attitude. This is typically done using a combination of attitude sensors and a mathematical model of the spacecraft.

Attitude estimation is the process of estimating a spacecraft's attitude. This is typically done using a combination of attitude sensors and a mathematical model of the spacecraft.

Trajectory control is the process of controlling a spacecraft's trajectory and velocity. This is typically done using a combination of thrusters and a mathematical model of the spacecraft.

Guidance is the process of guiding a spacecraft to a desired destination. This is typically done using a combination of sensors, actuators, and a mathematical model of the spacecraft.

Velocity control is the process of controlling a spacecraft's velocity. This is typically done using a combination of thrusters and a mathematical model of the spacecraft.

Reaction wheel control is the process of controlling a spacecraft's attitude using reaction wheels. Reaction wheels are momentum exchange devices that consist of a spinning flywheel. By changing the speed or direction of rotation of the flywheel, the spacecraft's angular momentum can be changed, thus controlling its attitude.

Thruster control is the process of controlling a spacecraft's attitude using thrusters. Thrusters are small rockets that produce thrust. By firing the thrusters in different directions, the spacecraft's attitude can be changed.

Magnetic torquer control is the process of controlling a spacecraft's attitude using magnetic torquers. Magnetic torquers are devices that produce a magnetic field. By changing the direction of the magnetic field, the spacecraft's attitude can be changed.