Measurement of Three Planetary Distances with a Single Observation

The observation for near one hour of the conjunction of Jupiter and Venus at less than 1 arcminute on May 17^th, 2000 (about 10 U.T.), has evidenced the possibility to measure the distances from the Sun of the Earth, Jupiter and Venus with a measurement of the speed of the relative motion of Venus with respect to Jupiter. The Kepler laws for the orbital velocity of the planets and the particular geometrical configuration occurred are required for this derivation.