The two Voyager space probes will surely go down as one of our greatest achievements and nearly 40 year on they're still doing there job. Those first pictures, up close and personal, with Jupiter, Saturn, Neptune and Uranus, though eclipsed by later missions, were nonetheless watershed moments in solar system science. They had a once in a lifetime opportunity to do a grand tour taking advantage of the alignment of the outer planets and made the most of it. The era of US space exploration that began with Mercury, then continued with Gemini and Apollo, and then culminated with the first Mars lander and Voyager are the high water mark of US engineering. And to think that much of it was done using slide rules and drafting tables.
Brian