Résumé : In this paper we describe the expected performance of JEM-EUSO. Designed as the first mission to explore the ultra-high energy universe from space, JEM-EUSO will monitor the Earth's atmosphere at night to record the UV (300-430 nm) tracks generated by the extensive air showers produced by ultra-high energy primary particles developing in the atmosphere. Studies of the expected aperture, the estimated exposure, as well as on the methods to infer arrival direction, energy, and Xmax of primary particles are presented. © 2013 COSPAR. Published by Elsevier Ltd. All rights reserved.