How can spacecraft attitude control impact mission planning?

1 Design considerations

One of the first steps in mission planning is to define the spacecraft design requirements, such as size, mass, power, thermal, and structural. These requirements depend on the mission objectives, the orbit, and the payload. However, they also depend on the attitude control system (ACS), which consists of sensors, actuators, and algorithms that enable the spacecraft to sense and control its attitude. The ACS design affects the spacecraft configuration, the mass distribution, the power consumption, the thermal balance, and the structural integrity. Therefore, mission planners need to consider the trade-offs between the ACS design and the other design requirements, and optimize them for the best performance and feasibility.

2 Performance metrics

Another step in mission planning is to evaluate the performance of the spacecraft and the mission. This involves defining and measuring various metrics, such as pointing accuracy, stability, agility, maneuverability, and fuel efficiency. These metrics depend on the attitude control modes, which are the operational states of the ACS that determine how the spacecraft responds to external disturbances and commands. The attitude control modes can be classified into passive or active, depending on whether they use external forces or internal actuators to control the attitude. They can also be classified into detumbling, stabilization, pointing, or slewing, depending on the desired attitude behavior. Mission planners need to select and optimize the attitude control modes for each mission phase and scenario, and ensure that they meet the performance metrics and the mission objectives.

3 Cost estimation

A crucial step in mission planning is to estimate the cost of the spacecraft and the mission. This involves accounting for various factors, such as development, testing, launch, operation, and disposal. These factors depend on the complexity, reliability, and lifespan of the spacecraft and its subsystems. The ACS is one of the most critical and expensive subsystems, as it requires sophisticated hardware, software, and ground support. The ACS cost depends on the type, number, and quality of the sensors and actuators, the level of redundancy and fault tolerance, the amount of propellant and power required, and the testing and validation procedures. Mission planners need to balance the cost of the ACS with the budget and the value of the mission, and seek ways to reduce or optimize the cost without compromising the performance or the safety.

4 Risk assessment

The final step in mission planning is to assess the risk of the spacecraft and the mission. This involves identifying and analyzing the potential sources of uncertainty, error, failure, or loss that could affect the mission success or safety. These sources can be internal or external, deterministic or stochastic, and independent or correlated. The ACS is one of the most vulnerable and influential subsystems, as it is exposed to various hazards, such as environmental disturbances, sensor noise, actuator degradation, software bugs, and human errors. The ACS risk affects the probability and the consequence of the mission failure or loss. Mission planners need to mitigate the risk of the ACS with appropriate methods, such as robust design, rigorous testing, fault detection and correction, contingency planning, and risk management.

5 Here’s what else to consider

This is a space to share examples, stories, or insights that don’t fit into any of the previous sections. What else would you like to add?