detumbling

Detumbling is the process of reducing and stabilizing the rotational motion of a spacecraft that is tumbling after deployment or during commissioning. The goal is to bring the body from a high angular velocity to a controlled, low-rate state that allows reliable attitude determination and subsequent pointing maneuvers. Detumbling is usually one of the first operations after a spacecraft enters orbit and is essential for safe deployment of deployables and solar arrays.

Attitude and rate metrics: angular velocity is reduced to below mission-specific thresholds, often a few degrees per second, with tighter requirements for precision pointing.

Methods: Passive detumbling relies on natural damping mechanisms such as gravity-gradient torques in elongated bodies, atmospheric drag at very low altitudes, or magnetically induced torques via magnetorquers. Active detumbling uses actuators to generate opposing torques, including magnetorquers, reaction wheels, control moment gyros, or thrusters.

Procedural approach: In many missions, a two-stage detumble is used: first, rapid reduction of spin rate with magnetorquers to a few degrees per second, then transition to fine attitude control.

Challenges: magnetic saturation of torquers, attitude-determination in high-dynamic conditions, and environmental disturbances like solar radiation pressure.

Outcome: Once detumbled, the spacecraft proceeds to attitude control, stabilization, and pointing tasks. Detumbling is a common and critical early step in on-orbit operations, enabling reliable mission operations and payload performance.