Complex sentence: He received the National Geographic Society's General Thomas D. White U.S. Air Force Space Trophy in June 1987, an award given to the individual who has made the most outstanding contribution to the nation's progress in space.
Split into simpler sentences: He received the National Geographic Society's General Thomas D. White U.S. Air Force Space Trophy in June 1987. The award is given to the individual who has made the most outstanding contribution to the nation's progress in space.