I know on the DSCS-III satellites that I used to control, there was no mechanism for disabling safe mode. I wouldn't be surprised if the same was true for Galileo.

Safe mode is designed to save a vehicle with critical malfunctions. It isn't something to mess with. On my satellites, it would go into safe mode if any of the following happened:

1. Loss of Earth Lock: if that happened, it was due to a loss of attitude control.

2. Battery discharge for more than 80 minutes.

3. Battery level of discharge below a certain threshold.

For Galileo, I suspect that the radiation is causing bit errors in the attitude control system, triggering safe mode. Even if it was possible to disable the safe mode triggers, the bit errors would still cause attitude errors, making it difficult to impossible to perform the imaging mission. It's also possible that the vehicle could spin up, making it difficult to recover. There's very little propellant left on Galileo, and recovering from a spin-up could use quite a bit of it.