Abstract <p>The paper describes an approach to designing an attitude control system for small spacecraft (SS), adaptive to possible failures of sensors and actuators. With this aim in view, the system loop includes its digital twin, which is designed to detect failures of measuring equipment using the predicted measurement values calculated based on onboard adaptive SS motion models. This approach increases the SS onboard computational burden, but prevents processing of unreliable measurement data in the feedback loop. Compensation for the failure of sensors and actuators is performed by reconfiguring the algorithmic support used to determine the SS attitude. To compensate for failures of actuators’ individual channels, an algorithm for SS attitude control is proposed, the structure of which has the form of even Fourier series.</p>