LL-030 - Gaia
Summary: The Gaia attitude may be described by four continuous functions of time q1(t), q2(t), q3(t), q4(t), which form a quaternion of approximately unit length. The quaternion formalism is elegant and computationally efficient, reducing the use of trigonometric functions to a minimum. As examples of the use of quaternions, I discuss the nominal scannig law, the inertial rotation of the instrument, and the determination of the instantaneous attitude from direction measurements.
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