Completed flybys thumb|Ganymede from Pioneer 10 (1973) The first spacecraft to approach close to Ganymede was Pioneer 10, which performed a flyby in 1973 as it passed through the Jupiter system at high speed. Pioneer 11 made a similar flyby in 1974. Data sent back by the two spacecraft was used to determine the moon's physical characteristics and provided images of the surface with up to resolution. Pioneer 10's closest approach was 446,250 km, about 85 times Ganymede's diameter.
Completed flybys thumb|Ganymede from Pioneer 10 (1973) The first spacecraft to approach close to Ganymede was Pioneer 10, which performed a flyby in 1973 as it passed through the Jupiter system at high speed. Pioneer 11 made a similar flyby in 1974. Data sent back by the two spacecraft was used to determine the moon's physical characteristics and provided images of the surface with up to resolution. Pioneer 10's closest approach was 446,250 km, about 85 times Ganymede's diameter.