Hi folks. Been beating my brain out trying to recall the author and title of a novella or novel I read years ago. Probably a story from the 1960's through 1980's. Rich family, with grandfather retired. Father running the family business. Grandson is brain damaged, with doting mother. In this future society, people (who can afford it) get their personalities recorded as often as possible so that they can be imprinted onto clone bodies if they get killed - a weird sort of immortality. There is a comet or alien ship entering the solar system that the grandfather feels is very important to humanity, but nobody else cares. He ends up imprinting his personality onto his strong bodied but mentally deficient grandson's body (over the protests of the mother) so that he can ride a rocket to rendezvous with the visitor in space. I recall this was a pretty good tale, but details have faded away. Want to say it was by a mainstream author like Poul Anderson, Clarke, etc, but searches of their works ring no bells. Anyone have any clue what I'm thinking of?