Abstract
A new tool is available to scientists for exploring the solar system, and modern-day explorers are discovering new worlds by radar. On 10 May 1961 a radar signal was beamed at the planet Venus, and for the first time in history the return echo was detected within a few minutes. A new value for the Astronomical Unit has been determined. The data indicate that Venus rotates slowly and that it is a better radio reflector than the moon.
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