Sponde.space

Why do sources give different orbits for Sponde?

Osculating versus mean elements, explained.

Published 2026-10-23

Look up Sponde and you’ll find different numbers.[1][2][3]

Three answers

  • Wikipedia: average distance 23.3 million km, period 728 days, eccentricity 0.189.[1]
  • NASA: mean distance about 23.8 million km, about 748 days.[2]
  • JPL mean elements: 23.5 million km, 738 days, eccentricity 0.32.[3]

Snapshots vs averages

An orbit computed at one moment is a snapshot that changes as the Sun and planets pull on the moon. Mean elements average those wobbles over long periods.[3]

Which to use?

This site uses JPL’s mean elements for its orbit diagram and quick facts, because they describe the long-term average path.[3]

Numbered citations link to the sources list on the Sponde overview page.

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