Yes, ASCERTAINED is a Scrabble word!

Letter values in Scrabble US: A 1, S 1, C 3, E 1, R 1, T 1, A 1, I 1, N 1, E 1, D 2.

Is it a valid word?

ASCERTAINED is a valid word in the official Scrabble dictionary (US), the UK Scrabble Dictionary and Words with Friends (ENABLE).

establish after a calculation, investigation, experiment, survey, or study
be careful or certain to do something; make certain of something
find out, learn, or determine with certainty, usually by making an inquiry or other effort
learn or discover with certainty

Also: find out, see to it.