8. Attitude Determination, Control, and Sensing
8.2 Subsystem Responsibilities
The Attitude Determination, Control, and Sensing (ADCS) system is responsible for the hardware and algorithms that estimate and control the spacecraft’s orientation. The ADCS system components are like the sensors and actuators of our body’s motor functions: the eyes, inner ear (for balance), nerves (sense of touch), arms, and core. The ADCS system is responsible for:
- sensing external cues from the environment that could resolve an attitude, analogous to orientation. Sensing is the most fundamental capability of the ADCS system.
- incorporating sensor measurements into an attitude determination algorithm that resolves attitude. Determination cannot happen without some kind of sensing.
- controlling the spacecraft’s attitude by sending control algorithm commands to actuators.
- pointing, tracking, and/or slewing along a trajectory with a level of precision and accuracy defined by the needs of the payload or mission.
Wallops engineer Scott Heatwole and his team are developing a precision attitude sensor or star tracker that would be able to locate points of reference, or, in other words, stars, during daylight hours. Heatwole specifically developed the technology for the Wallops Arc Second Pointer. Credits: NASA/Patrick Black.
During the design process, the ADCS specialist:
- selects sensors and actuators that ultimately yield precision pointing or tracking accuracy and precision.
- conducts analysis on external and internal forces and torques to discover contributions to spacecraft dynamics due to these disturbances (common for spacecraft with components that vibrate). This may include dynamic simulation analysis.
- coordinates with the structures and mechanisms specialist to place and mount sensors and actuators with unique requirements, like an unoccluded field of views or close placement to the center of mass.
- calculates and codes algorithms to estimate position and attitude states, and also controls spacecraft attitude to the required accuracy and precision. This may include development within a simulation environment.
