They did comprehensive risk mitigation actions since last may :
- They tested every MOSFET lot identified at risk (International Rectifier n-MOSFETs generation 5, 6 and 7), in application conditions. They actually asked every subcontractor for every instrument and equipment on the spacecraft to send them remaining parts in their inventory.
- Because of temperature dependent effects and time dependent effects (mainly concerning annealing of total ionizing dose damage), they could only test up to the mission baseline total ionizing dose constraint. They found the tested parts were to be suitable for the mission, however since they only had a limited number of parts, they do not know the real margin they have, especially if the temperature conditions differ significantly from the baseline.
- So in order to monitor the parts degradation during the actual flight, they designed this summer what they call a "canary box": an equipment with the most sensitive lots of MOSFET onboard, with telemetry to actually measure the main electrical parameters that will degrade with total ionizing dose (mainly the gate-to-source voltage threshold).
- If they measure a higher than expected degradation on the canary box, they will implement mitigation actions (such as shutting down some instruments to limit their total ionizing dose degradation or heating them up to increase annealing)
In conclusion, they feel pretty safe to me...