The JEM - EUSO collaboration intends to study high energy cosmic ray showers using a large downward looking telescope mounted on the Japanese Experiment Module of the International Space Station . The telescope focal plane is instrumented with approx.300k pixels operating as a digital camera , taking snapshots at approx . 1MHz rate . We report an investigation of the trigger and reconstruction efficiency of various algorithms based on time and spatial analysis of the pixel images . Our goal is to develop trigger and reconstruction algorithms that will allow the instrument to detect energies low enough to connect smoothly to ground - based observations .