The term space probe refers here to those spacecraft that have escaped earth-orbit. The former Soviet Union was first in this area, as they had been with other space shots. In 1959 they launched Luna 1, which missed the Moon by 3,728 miles (5,998 km). They followed that flight with a spectacular circumlunar orbit by Luna 3, which gave us our first pictures of the far side of the Moon.

The development of probes in the United States also revolved around the Moon at this time. After several unsuccessful attempts to reach the Moon with the Pioneer series, the National Aeronautics and Space Administration (NASA) launched the Ranger series. It planned to crash-land the spacecraft onto the moon's surface, taking photos up until impact. The first few probes were unsuccessful, but the last three-- Ranger 7, Ranger 8, and Ranger 9--took over 17,000 pictures beginning in 1963.

The former Soviet Union scored another first in...