In normal operation mode, RSI is not exposed to direct Sun irradiation, as long on-ground nominal procedure for Mission Programming is respected. The Spacecraft contingency mode is the so-called Safe Mode, in Safe mode, RSI can be exposed for a short time to direct Sun irradiation, as shown by AOCS detailed simulations. This may happen only during the initial transient phase of ASH mode, when attitude has not yet fully converged. The aim of this paper is to discuss that if Sun exposure periods are compatible with RSI constraints. There are two factors to be taken into consideration; one is the Sun exposure period (duration), the other is the Sun direct illumination in sensor and filter.