The general context of this short communication, is the development and the application of the guaranteed state estimation observer–based interval techniques, to improve the navigation unit used in space missions. A H∞ constraint is also considered in the design of the interval observer, to formulate robustness performance against sensor misalignment errors, noises and other unknown inputs that may affect the estimation. The application support is the Microscope satellite which is a scientific mission launched in 2016. A functional engineering simulator (FES) of the Microscope mission is used to assess the performance of the proposed state estimation interval techniques. The FES includes highly representative models of sensors and actuators, and Dynamics Kinematics and Environment (DKE) models. The environment modules (within DKE) contain the spatial disturbances that affect the rotational and translational dynamics of the satellite. The considered disturbances are the magnetic field, the aerodynamic drag, the gravitational disturbances, the solar and the albedo radiations.