Thermo-mechanical design of the optical head for MAJIS experiment

The Moons And Jupiter Imaging Spectrometer is an experiment selected for the Jupiter Icy Moons Explorer ESA mission in the framework of the Cosmic Vision 2015–2025 Programme. The instrument will perform imaging spectroscopy of the Galilean System in the visible and near infrared ranges. This work is focused on the design of the optical head of the instrument, a quite critical task considering that the optical bench must support, in addition to the optics, about 5 kg of radiations shielding required because of the tough radiative environment. Moreover, the two passive radiators cooling the infrared detector and the optical bench are mounted on the optical head to maximize their efficiency. As result the overall mass to be supported is 18 kg, i.e. about five times larger than that allocated for the optical bench structure in the mass budget. Minimization of the optical bench mass therefore, guides the structural design that shall warrant a proper stiffness and resistance against the expected mechanical loads. Finite element models of the optical head have been developed and thus the design feasibility has been proved. An optimized design has been developed providing for a 20% mass saving with respect to the feasibility study. Finally, dynamic testing of a structural mock-up completes the design providing validation of the finite element models.