 Apollo astronauts frequently aligned their spacecraft inertial navigation platforms and determined their positions relative to the Earth and Moon by sighting sets of stars with optical instruments . As a practical joke , the Apollo 1 crew named three of the stars in the Apollo catalog after themselves and introduced them into NASA documentation . Gamma Cassiopeiae became Navi – Ivan ( Gus Grissom 's middle name ) spelled backwards . Iota Ursae Majoris became Dnoces – " Second " spelled backwards , for Edward H. White II . And Gamma Velorum became Regor – Roger ( Chaffee ) spelled backwards . These names quickly stuck after the Apollo 1 accident and were regularly used by later Apollo crews . 
