The astronomical unit determined by radar reflections from Venus

Abstract

Radar reflections from the surface of the planet Venus at a wavelength of 12.5 cm yielded a value of the astronomical unit of 149 598 845+250 (p.e.) km, or a solar parallax of 8"7940976+147 based on an earth radius of 6378 145 m. The computations were accomplished utilizing Doppler-frequency-shift and time-of- flight observations (range measurements) in conjunction with the "best" available planetary ephemerides of the earth and Venus. The investigations yielded proof of the transparency of the Venus atmosphere at 12.5 cm and some information on the radius of Venus. Systematic errors in the published ephemerides are also discussed.