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The mean rotation rate of Venus from 29 years of Earth-based radar observations

  • Author(s): Campbell, BA
  • Campbell, DB
  • Carter, LM
  • Chandler, JF
  • Giorgini, JD
  • Margot, JL
  • Morgan, GA
  • Nolan, MC
  • Perillat, PJ
  • Whitten, JL
  • et al.

We measured the length of the Venus sidereal day (LOD) from Earth-based radar observations collected from 1988 to 2017, using offsets in surface feature longitudes from a prediction based on a 243.0185d period derived from analysis of Magellan mission images over a 487-day interval. We derive a mean LOD over 29 years of 243.0212 ± 0.0006d. Our result is consistent with earlier estimates (but with smaller uncertainties), including those based on offsets between Venus Express infrared mapping data and Magellan topography that suggest a mean LOD of 243.0228 ± 0.002d over a 16-year interval. We cannot detect subtle, short-term oscillations in rate, but the derived value provides an excellent fit to observational data over a 29-year period that can be used for future landing-site planning.

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