Neil deGrasse Tyson.

The link is to a piece on Patheos detailing the accusation made by Tchiya Amet El Maat, who was a grad student at UT-Austin while Tyson was there. Her accusation sounds much like those against Bill Cosby: she accepted a drink from him that was supposed to be water, then passed out. The Patheos piece was written by a person who's admittedly a fan of Tyson and who quoted him in his book No Sacred Cows.

Apparently El Maat made the accusation three years ago in a blog post, and nobody said much of anything; I don't recall hearing about it the, or last year when another blogger repeated her claim.