  Comet C/2012 S1 (ISON) shows strange photometric behavior compared to many
past comets. Shortly after its discovery, majority of astronomers expected its
surviving until perihelion passage. Unprecedented evolution of its photometric
parameters nearly 2 AU from Sun, pushed this comet under survival line defined
by formula of John. E. Bortle, where ~70% comets in his analysis disintegrated.
However comparison with photometric behavior of group of past disintegrated
comets showing large differences and ISON doesn't seems to be typical member of
this group. In other hand, compared to surviving, dynamically new comets which
were observed far away from Sun and survived its perihelion passage, ISON
showing peculiar gradual decrease of its activity, probably caused by
exhaustion of active fractions of its nucleus.
