  Mini-EUSO is a mission of the JEM-EUSO program flying onboard the
International Space Station since August 2019. Since the first data acquisition
in October 2019, more than 35 sessions have been performed for a total of 52
hours of observations. The detector has been observing Earth at night-time in
the UV range and detected a wide variety of transient sources all of which have
been modelled through Monte Carlo simulations. Mini-EUSO is also capable of
detecting meteors and potentially space debris and we performed simulations for
such events to estimate their impact on future missions for cosmic ray science
from space. We show here examples of the simulation work done in this framework
to analyse the Mini-EUSO data. The expected response of Mini-EUSO with respect
to ultra high energy cosmic ray showers has been studied. The efficiency curve
of Mini-EUSO as a function of primary energy has been estimated and the energy
threshold for Cosmic Rays has been placed to be above 10^{21} eV. We compared
the morphology of several transient events detected during the mission with
cosmic ray simulations and excluded that they can be due to cosmic ray showers.
To validate the energy threshold of the detector, a system of ground based
flashers is being used for end-to-end calibration purposes. We therefore
implemented a parameterisation of such flashers into the JEM-EUSO simulation
framework and studied the response of the detector with respect to such
sources.
