The Soviet Union’s successful Zond-5 space mission in 1968 prompted NASA to speed up the Apollo program—ultimately driving it to its successful conclusion the following year.

In March 1968, the Soviet Union had a partial success with Zond 4. With this launch, they were able to take the spacecraft out to lunar distances (though not around the Moon) even if navigation system ...

Every 378 days, Saturn swings into opposition, bringing it closer, brighter, and nearly 10 times easier to observe than at ...