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A satellite, especially a geostationary satellite which may be stabilized in its three major axes and which has a spin wheel or momentum wheel supporting a position control system and which also has an engine or propelling system, is controlled by actuating the spin or momentum wheel at the latest w

A satellite, especially a geostationary satellite which may be stabilized in its three major axes and which has a spin wheel or momentum wheel supporting a position control system and which also has an engine or propelling system, is controlled by actuating the spin or momentum wheel at the latest when the satellite is in a phase of being transferred from one orbit to another orbit. Thereafter, the satellite is rotated about its axis which extends in parallel to the axis of the spin wheel or momentum wheel whereby the rotational impulse of the satellite is smaller than that of the momentum wheel. The stabilizing of the satellite relative to the three major axes is then made at the point in time when the satellite is to change from one orbit to another orbit whereupon the engine system for reaching the new orbit is switched on. The thrust of the engine system is so dimensioned that the position control system intended for a subsequent mission retains its orientation even during the phase of changing orbits. At least one momentum or spin wheel is effective in the position control of the satellite in each operational phase of the satellite. A drive or propelling system for a position control in the three axial directions is provided along with liquid fuel drive engines for the orbit change and for the orbit correction.

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A method for attitude control and trajectory change of a satellite having a mission encompassing a transfer phase wherein said satellite is spin-stabilized and a latter phase wherein said satellite is three-axis stabilized, said satellite having a momentum wheel, an attitude control system and propu

A method for attitude control and trajectory change of a satellite having a mission encompassing a transfer phase wherein said satellite is spin-stabilized and a latter phase wherein said satellite is three-axis stabilized, said satellite having a momentum wheel, an attitude control system and propulsion means, said method comprising the steps of: activating said momentum wheel at the latest in the transfer phase of the mission; rotating said satellite about an axis of the satellite which is parallel to the spin axis of the momentum wheel with a smaller angular momentum than that of said momentum wheel during said spin-stabilization phase; substantially changing the trajectory of said satellite from said transfer phase to a substantially different trajectory and stabilizing said satellite along three axes at the moment of said changing of trajectory; and selecting the thrust of said propulsion means to be effective to maintain proper satellite attitude during said changing of trajectory and for a period of three-axis stabilization after said trajectory is changed.