What is attitude control and why is it necessary for spacecraft?

Attitude control maintains a spacecraft's orientation in space. It is essential for: Pointing payloads (antennas toward Earth, solar panels toward Sun, telescopes toward targets), Thermal management (controlling which surfaces face Sun), Communications (antenna pointing for link budget), Propulsion (orienting thrusters for maneuvers), and Power generation (solar panel orientation). Components include: Sensors (star trackers, sun sensors, gyroscopes, magnetometers) for attitude determination, and Actuators (reaction wheels, control moment gyros, thrusters, magnetic torquers) for attitude control. Control modes include spin stabilization, 3-axis stabilization, and gravity gradient. Pointing accuracy requirements range from degrees (communication satellites) to arc-seconds (space telescopes).