Three years later, radar observations by Americans Gordon Pettengill and R. Dyce, using the 300-meter Arecibo Observatory radio telescope in Puerto Rico, showed conclusively that the planet's rotational period was about 59 days.
Tre år senere viste radarobservationer af amerikanerne Gordon Pettengill og R. Dyce, der brugte 300-meter radioteleskopet ved Arecibo Observatoriet i Puerto Rico endeligt at planetens rotationsperiode var omkring 59 dage.