Foresight ability tells you your chance of success before invasion cost 25 badges.

% = 100%*invasion attack/(3*total invasion defense)

total invasion defense= attack+ defense+ invasion defense

You have a calculator app on your computer.

caps at 90% and the atmospheric decimators' bonus are applied after. So if you get 86% or higher with both on you should get the planet 100% of the time.

Not quite... The decimator bonus IS applied after everything else, but the chance still caps at 90%. There is ALWAYS at least a 10% chance of failing. Otherwise, your point is valid. Just use the calculator or make a spreadsheet like I did. I've got all my attack info listed and it calculates how much invasion defense is equal to what percent chance.

I thought so too, but I have failed with a 93% chance once, with one on. I didn't have the foresight to take a screen shot and I am not one to complain about the almighty RNG.