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The pointed star camera (Toronto) is able to lock on magnitude 4 stars
in daytime at float. Its orientation with respect to the payload is measured
by two absolute encoders (16 bit).
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The pointed star sensor (INGV + La Sapienza) locks on the sun center and
tracks it by means of two 4 quadrants photodiodes. Its orientation is measured
by two absolute encoders (16 bit). It is mounted on the sun side of the
gondola, and is covered and painted white to avoid overheating.
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The azimuth scans are obtained by means
of an azimuth pivot developed at IFAC-CNR and mounted between the payload
and the flight chain.
The pivot has a top motor acting against the flight chain, and a lower
motor spinning a flywheel. During normal scans, only the lower flywheel works.
Acting against the flight chain is needed only to dump momentum when needed,
or to reorient the payload towards a distant direction.
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