Jupiter's moons in COSMOS: four navigable Galilean satellites

Measured facts

Io radius

1,821 km419,988 km to 423,535 km from Jupiter.

Europa radius

1,561 km664,442 km to 677,708 km from Jupiter.

Ganymede radius

2,631 km1,067,323 km to 1,073,522 km from Jupiter.

Callisto radius

2,410 km1,868,767 km to 1,896,664 km from Jupiter.

Why they are stored separately

A moon orbiting a planet hundreds of millions of kilometres away cannot be stored precisely in an Earth-centred archive: the small orbit would be a rounding error inside a huge vector. COSMOS stores each Galilean moon relative to Jupiter and composes the two states at runtime, which is why these pages can quote real distance ranges.

What you can and cannot see

• Measured: each moon’s radius, and its position relative to Jupiter at every date inside the archive window.
• Not integrated: surface imagery. These four are true-size educational spheres, and their real surfaces are not rendered.
• Not implemented: Jupiter’s smaller inner and outer satellites, orbital path lines, mutual shadowing and tidal or volcanic activity.