My reply may not be exactly what you want to hear, but I believe it is a "close" answer. You will have to perform your own tests to be certain.
PSOC 5LP is a CMOS device, with fairly large geometry. I have been involved in the oilfield since 1978, always in engineering, and since 1982, always in R&D. CMOS is known to be generally heat tolerant.
The failure mode for IC's in heat is generally electrons going where you do not want them to go. This is also the case for radiation exposure. One of our indicators for radiation survivability is heat survivability.
We have found that the PSOC5LP will reliably work at 300F, and under most circumstances, to 350F. That implies it has a lot of radiation tolerance.
The larger CMOS geometries (with lots of extra available electrons) can afford to have a few electrons vanish due to radiation combination effects. They can support some electron leakage for those same reasons.
Unfortunately, all the shielding you can do for protection equals weight. Even so, very minor shielding (i.e. small layer of water (for alpha radiation) or lead (for neutrons, etc) can lead to greater survivability.
Currently, we use PSOC5 LP as a Gamma Ray pulse Counter, and a Neutron Pulse Counter, with sources up to 20 Curie. We no longer keep or use such sources, so it is up to our customers to do final testing. (Not coincidently, the entire industry is moving away from fixed sources due to government regulations. At some point in the future, no one will be able to use fixed radiation sources while exploring for energy.)
So, in my opinion, which is worth zero, your chances for using a PSOC 5LP in a cubesat is fairly good.
One thing to keep in mind. In my testing (up to 400F), I found that sometimes the PSOC5LP mems oscillator did not want to start up from 0 volts at the higher temperatures. Keeping a very low bias (1volt or so) on the chip allowed full CPU reset, and the oscillator to operate even at higher temperatures. That oscillator is required to work during startup for the PSOC5LP to work, even with an external crystal.