Fifteen Years of Radar Reveal Venus’s Most Basic Facts

Planetary scientists agree that a Venusian day is a little longer than 243 Earth days, but for decades their measurements have disagreed about the additional number of minutes and seconds. What’s more, those measurements haven’t been precise enough to infer other fundamental properties of Venus, like how the length of a day changes, the tilt of the planet’s spin relative to its orbital plane, and the precession of that tilt. Without these precise values, a craft attempting to land on Venus might miss its target zone by as much as 30 kilometers.

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