Yes, I read that this morning I had read a few of his novels ("Rendezvous with Rama" and "Base Venus" among others).
The real sign that someone has become a fanatic is that he completely loses his sense of humor about some important facet of his life. When humor goes, it means he's lost his perspective.
He invented the communications satellite, and had a good show on the Discovery Channel years ago called 'Mysterious World', which dealt with paranormal claims and unlike most shows about the paranormal, it was dealt a skeptical perspective.
He wasn't as vocal as Carl Sagan, but he'll be missed.