What was the series that Ron Hubbard began writing but died before finishing?

The series that Ron Hubbard began writing but died before finishing is called Mission Earth.

It is a science fiction series that tells the story of a group of aliens who come to Earth on a mission to save humanity from itself. Hubbard wrote ten books in the series before his death in 1986.

The eleventh and final book, The Invaders Plan, was completed by his son, L. Ron Hubbard Jr., and published posthumously.