 Dactyl 's orbit around Ida is not precisely known . Galileo was in the plane of Dactyl 's orbit when most of the images were taken , which made determining its exact orbit difficult . Dactyl orbits in the prograde direction and is inclined about 8 ° to Ida 's equator . Based on computer simulations , Dactyl 's pericenter must be more than about 65 km ( 40 mi ) from Ida for it to remain in a stable orbit . The range of orbits generated by the simulations was narrowed down by the necessity of having the orbits pass through points at which Galileo observed Dactyl to be at 16 : 52 : 05 UT on 28 August 1993 , about 90 km ( 56 mi ) from Ida at longitude 85 ° . On 26 April 1994 , the Hubble Space Telescope observed Ida for eight hours and was unable to spot Dactyl . It would have been able to observe it if it were more than about 700 km ( 430 mi ) from Ida . 
