Determining the spacecraft Foton M-4 attitude motion

The paper presents the results of reconstruction of the spacecraft Foton M-4 attitude motion in the single-axis solar orientation mode. The reconstruction is based on processing the measurements of two vectors: the spacecraft angular rate and the strength of the Earth magnetic field. The processing technique uses kinematical equations of the attitude motion of a rigid body. In its framework, the measurement data of both types, collected on a time interval, are processed jointly. The angular rate data are interpolated by piecewise linear functions and those functions are substituted in kinematical equations for components of the quaternion, which defines a transformation of the spacecraft coupled coordinate system to the inertial one. The equations obtained present the kinematical model of a spacecraft attitude motion. The solution of the equations, which approximates the real motion, is found by the least squares method from the condition of the best agreement between measurement and calculation data of the magnetic strength. The technique allows to reconstruct the attitude motion on time intervals more than 10 hours. The found reconstructions are used for calculation of residual accelerations onboard the spacecraft.