Hubble
Edwin Hubble was an American astronomer for whom the HST was named after. He was the first person to discover that there are large-scale galaxies beyond the Milky Way and that they are distributed almost uniformly in all directions. This I believe is a picture of him with the 100 -in. (254 -cm) telescope at Mt. Wilson Observatory where he discovered what is now known as Hubble's Law. He never got to see his namesake because of his death in 1953.