The planetary exploration program

The U. S. program for space exploration of the planets began with the Mariner 2 flyby of Venus in 1962. Since then a series of Mariners have gone to Mercury and Mars, in addition to Venus. Pioneer-class spacecraft have flown through the asteroid belt and have passed by Jupiter. The Viking mission carried Out a spectacularly successful series of measurements at Mars. These past missions will be followed shortly by recently launched Voyager flybys of Jupiter and Saturn in 1977 and by Pioneer probes and orbiter to Venus in 1978. These missions have stressed exploration. Now there are two additional goals involving the well-being of Man which are looming on the space horizon.