Use of gravitational orientation mode for International Space Station

We investigate the possibility of using the mode of gravitational orientation for International Space Station. The investigation is carried out by mathematical modelling of the station attitude motion under the action of the gravitational and aerodynamic torques. We show that the station can be at the triaxial gravitational orientation for a few days if the initial conditions of its attitude motion are installed in a proper manner. The longitudinal axis of its Service unit makes small oscillations near the local vertical in this mode, whereas the rotation axis of solar arrays of this unit makes small oscillations with respect to the station orbital plane. When the initial conditions are installed with errors, only single-axis mode of gravitational orientation can be realized. In this mode the longitudinal axis of Service unit is directed approximately along the local vertical, the station rotates around this axis or makes slow oscillations with large amplitude with respect to it.