On Tue, 14 Aug 2018 17:51:40 -0700 (PDT), RichA
wrote:

Reasonably fast mission as well! Though I wonder if the thing will
last as long as they say it will. Its heat shield will stop the IR
and UV, but not the cosmic rays.

However the cosmic rays originate from the cosmos, outside the solar
system, so this problem is equally hard for interplanetary space
probes not approaching the Sun. Satellites in LEO get some protection
from the Earth's magnetic field, but outside that you get no
protection at all from the cosmic rays.