 243 Ida ( / <unk> / ) is an asteroid in the Koronis family of the asteroid belt . It was discovered on 29 September 1884 by Austrian astronomer Johann Palisa and named after a nymph from Greek mythology . Later telescopic observations categorized Ida as an S @-@ type asteroid , the most numerous type in the inner asteroid belt . On 28 August 1993 , Ida was visited by the unmanned Galileo spacecraft , while en route to Jupiter . It was the second asteroid visited by a spacecraft and the first found to have a natural satellite . 
