  In 2007, the M-type binary asteroid 22 Kalliope reached one of its annual
equinoxes. As a consequence, the orbit plane of its small moon, Linus, was
aligned closely to the Sun's line of sight, giving rise to a mutual eclipse
season. A dedicated international campaign of photometric observations, based
on amateur-professional collaboration, was organized and coordinated by the
IMCCE in order to catch several of these events. The set of the compiled
observations is released in this work. We developed a relevant model of these
events, including a topographic shape model of Kalliope refined in the present
work, the orbit solution of Linus as well as the photometric effect of the
shadow of one component falling on the other. By fitting this model to the only
two full recorded events, we derived a new estimation of the equivalent
diameter of Kalliope of 166.2+/-2.8km, 8% smaller than its IRAS diameter. As to
the diameter of Linus, considered as purely spherical, it is estimated to
28+/-2 km. This substantial "shortening" of Kalliope gives a bulk density of
3.35+/-0.33g/cm3, significantly higher than past determinations but more
consistent with its taxonomic type. Some constraints can be inferred on the
composition.
