  Measurement of the number of spectators in nucleus-nucleus collisions could
be used to determine the number of participant nucleons involved in the
interaction, i.e. get information about collision centrality. However, at
energies of the NICA collider, energy resolution of the forward hadron
calorimeter is insufficient for separation amplitude corresponding to different
number of spectators. Uncertainty in the number of spectators leads to a large
error in determining centrality. For central events inaccuracy in determining
the collision parameter is about 40%, for peripheral ones, no better than 30%
at a beam energy of 2.5 AGeV. The multiplicity scintillator detector will allow
to obtain more accurate data. A method is proposed for determining the
centrality, taking into account the real MPD installation geometry.
