NASA FACTS is a collection of the United States' National Aeronautics and Space Administration's science series, NASA FACTS, intended as "easy-to-understand explanations of scientific phenomena involved in projects undertaken by NASA". The NASA FACTS SCIENCE SERIES was published frequently at irregular intervals, each presenting "an analysis of a particular subject within program perimeters and scientific disciplines of interest to NASA".
(quote from this cover letter from Director, Educational Programs Division of NASA's Office of Public Affairs, James V. Bernardo.)
A complete overview of NASA FACTS on wikisource is found here.