ESA JUICE Mission JUpiter ICy moons Explorer which is planned for launch in 2022 would be consisted of 11 science instruments. For one of them, SWI (Submillimetre Wave Instrument), the dedicated Radiator was designed due to requirement for low operational temperature of crucial instrument subsystem. Located outside of the spacecraft and facing the Deep Space; exposed to highly radiative environment and high temperature gradients between Earth, Venus and Jupiter orbits; robust against launch vibrations; light-as-possible and optimized to provide maximal thermal efficiency. The design solution, which would successfully fulfill these often counteracting requirements occurred to be non-trivial. Presented design approach shows the balanced and optimized response for initial requirements, including the description of thermal performance modelling using ESATAN and structural FEM analysis calculated in NASTRAN.