Io: a measured orbit and radius, with surface imagery still pending

Measured facts

Classification

Galilean natural satellite

Parent body

Jupiter

Mean radius

1,821 kmPublished mean radius stored as renderer geometry.

Mean diameter

3,643 km

Mean radius in Earth radii

0.286

Appearance

Temporary educational representation

What you are looking at

Io orbits close enough to Jupiter that its position must be stored relative to Jupiter. COSMOS composes the interpolated moon state with the same-epoch Jupiter centre, so the moon keeps local precision instead of inheriting a large planet vector.

The visibility marker appears only when the verified child archive is ready and the camera is inside a bounded Jupiter-system context. Markers never enlarge the physical body.

The sphere itself is a labelled educational proxy: a real radius at a real position, with no spacecraft image bound to it yet.

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

423,438.8 km on 2026-08-29Magnitude of the Jupiter-centred position vector at the recorded ephemeris snapshot.

Closest measured approach to Jupiter

419,988.3 km on 2038-10-21

Farthest measured separation from Jupiter

423,534.6 km on 2030-11-22

Mean measured separation

421,769.2 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

2.0 h sampling · 7.6 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 Io. Educational geometry limit only; no observational surface imagery is integrated for this body yet.

Appearance status

Temporary educational representation

Renderer provider id

io-visual-v1

Geometry

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

Rotation model

IAU_IO — 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 Voyager or Galileo surface mosaic is integrated; the appearance is explicitly incomplete.
• Io’s volcanic resurfacing, plumes and sulphur colouring are not represented, because COSMOS will not approximate an observation it does not have.
• 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.