Left panels: motion of the spin axis (i.e., the direction of the principal axis of inertia) in latitude (top) and longitude (bottom) as a function of time, over a typical period of 70 min, including two manoeuvres clearly identified by the large excursions in latitude and longitude. The dwell periods show the much smaller amplitude motions due to nutation and drift arising from solar radiation pressure. Top right: motion of the spin axis in Galactic latitude and longitude for a sequence of three manoeuvres and dwells. The attitude measurements during the slew are not filtered and are therefore very noisy; the measurements during each dwell are strongly clustered and show up as dense spots. Bottom right: zoom on a portion (about 30 min) of a dwell showing clearly the periodic motions which are a combination of the drift and residual nutation (period ~5.4 min).
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