Add to ORKGThe next generation of experiments devoted to the study of the cosmic rays spectrum above 10(20) eV will be most likely done by means of space based detectors. In order to detect the fluorescence and Cerenkov signal generated by an EAS in atmosphere, severe requirements on the photon collection efficiency and on the triggering capability need to be met. In this paper we report about of preliminary studies of the triggering efficiency of a space based detector as a function of the main detector parameters. All results are obtained by means of a detailed simulation of the shower development, atmospheric response, detector geometry and electronics and trigger behavior in realistic conditions based on the ESAF package, the EUSO Simulation and A...