For reacquisition of the attitude of a satellite wholly or partly three-axis stabilised, the method tests whether an Earth detector detects the Earth (test 1) and whether a star detector detects a star of magnitude at least approximately equal to that of a given reference star (test 2): … … * case a : if tests 1 and 2 are positive, the Earth and the said star are captured, and the method tests the coherence over time of the roll information supplied by the Earth and star detectors : in the case of non-coherence it passes to case b; … * case b : if only test 1 is positive, the Earth is captured and the satellite is commanded in rotation in yaw until test 2 is satisfied; the said star is captured and the method proceeds to the coherence test provided for in case a; … * cases c and d : if test 1 is negative, the pitch speed is reversed during a given time at most; if test 1 becomes positive, test 2 is carried out: if test 2 remains negative, the method passes to case b, or else it passes to the coherence test; in default it passes to sun acquisition mode. … …IMAGE…
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