Ganymede: the largest moon, measured but not yet imaged

Measured facts

Classification

Galilean natural satellite

Parent body

Jupiter

Mean radius

2,631 kmPublished mean radius stored as renderer geometry.

Mean diameter

5,262 km

Mean radius in Earth radii

0.413

Appearance

Temporary educational representation

What you are looking at

Its mean radius is stored in the same table that supplies every body in the scene, so relative sizes remain comparable across the whole Solar System.

The moon shares the Jovian orientation model with Jupiter, so the pair cannot drift into inconsistent reference frames.

The visible object is a mean-radius educational sphere.

Measured distance from Jupiter

These figures are magnitudes of the moon’s Jupiter-centred position vector, sampled once per day across 2020-01-01 00:00 TDB through 2040-01-01 00:00 TDB. They are distances from the centre of Jupiter, not from Earth, and they change because the orbit is not a perfect circle.

Distance from Jupiter at the snapshot epoch

1,073,013.3 km on 2026-08-29Magnitude of the Jupiter-centred position vector at the recorded ephemeris snapshot.

Closest measured approach to Jupiter

1,067,323.2 km on 2037-06-25

Farthest measured separation from Jupiter

1,073,522.1 km on 2033-06-30

Mean measured separation

1,070,432.7 kmSampled once per day across 2020-01-01 00:00 TDB to 2040-01-01 00:00 TDB (7,306 samples).

Archive cadence and held-out error

6.0 h sampling · 5.7 km worst held-out errorThe archive stores this moon relative to Jupiter so the large planet vector is not repeated per moon.

Delivery and camera limits

The camera stops at 1.08 mean radii for Ganymede. Educational geometry limit only; no observational surface imagery is integrated for this body yet.

Appearance status

Temporary educational representation

Renderer provider id

ganymede-visual-v1

Geometry

mean-radius-sphereMean-radius sphere; no ellipsoid or terrain displacement yet

Rotation model

IAU_GANYMEDE — pck00011 (2022-12-27)Source: https://naif.jpl.nasa.gov/pub/naif/generic_kernels/pck/pck00011.tpc

Limitations COSMOS discloses

• Appearance incomplete; no observational surface or atmosphere claimed
• No global mosaic is integrated; the USGS/Voyager and Galileo mosaics remain candidates under review.
• No terrain, groove terrain or crater displacement is present.
• Position is interpolated inside 2020-01-01 00:00 TDB through 2040-01-01 00:00 TDB; the ephemeris snapshot labelled 2026-08-29 00:00 TDB is the epoch used for the figures above.