No American spacecraft had set out for a planet since a Pioneer mission went to Venus in 1978.

Both probes contained more sophisticated instrumentation than the previous Pioneer missions, including a camera capable of taking much higher resolution images.

The Pioneer missions were the first spacecraft to take close up pictures of Jupiter and its moons.

As the name suggests, Pioneer missions paved the way for later probes.

The Pioneer mission to Venus comprised two components, launched separately.

Spaceflight article from 2005 on the 45th anniversary of Pioneer 5 mission.

The Pioneer mission consisted of two components, launched separately: an orbiter and a multiprobe.

The Pioneer missions obtained the first close-up images of Jupiter's atmosphere and several of its moons.

Comparison of images showed that the Red Spot had changed hue since the Pioneer missions, turning from orange to dark brown.

Additionally, the Pioneer mission to Venus consisted of two components, launched separately.