If I remember correctly, The construction and launch of the Voyager spacecrafts in the early 1970s had an urgency as there was to be an unusual lineup of the outer planets (Jupiter, Saturn, Uranus and Neptune). At that time, we had only been "space-faring" for about 10 years!

Does this planetary lineup really occur infrequently? And if so, when is the next time that a Voyager-like mission (using today's technology), could be mounted?