Asteroid Ida and its moon. Coloured image gathered by the Galileo spacecraft showing Asteroid 243 Ida and its tiny moon (right), provisionally known as 1993(243)1. This picture was the first conclusive evidence that an asteroid can have a satellite. Ida is a member of the Koronis family of asteroids, and is about 56 kilometres in length. The moon is about 1.5 kilometres in diameter, and is thought to orbit about 100 kilometres from Ida's centre. This image was taken on 28 August 1993, at a distance of 10,870 kilometres from Ida. This was the second asteroid encounter by the Galileo spacecraft on its way to Jupiter.