ISAE's EntrySat student satellite is one of the 10 QB50 In-Orbit Demonstration (IOD) satellites. The scientific objectives have been defined in collaboration with ONERA and are the following : to refine the atmospheric modeling between 120 and 350 km and to refine the aerodynamic coefficients modeling. Aerodynamic forces and associated kinematics (position, attitude motions) will be evaluated. EntrySat will perform these measurements during orbit decay phase and destruction phase. This paper presents the EntrySat mission, in board instrumentation and pre-flight analysis.