...On the CYGNSS spacecraft UV and radiation exposure lead to a marked loss of sensitivity on some of the optical sensors on board, resulting in up to a 20% degradation of the signals in the first month of operations. Luckily the system rapidly stabilized after that, but for a time there was a danger that the spacecraft could be partially blinded, resulting in a chance of loss of the vehicle if safe mode was triggered.
Question: Why did some of the optical sensors of CYGNSS satellites suffer UV and radiation-induced loss of sensitivity? Was this unexpected? If so, why?
Was atomic oxygen involved as well?
See also the other answer to How fast do optical surfaces get dirty or damaged in space? for more on damage mechanisms