NASA gets a lot of well deserved criticism, but their space probes and the knowledge they get from them is still generations ahead of any other country. Aerobraking, gravity assisted speed and direction adjustments, navigation in deep space, were science fiction only a couple of decades ago. Now NASA is so experienced at it, these are almost routine.
Each one of those planetary missions builds on what has been done before, but are essentially one-offs, and the work to figure out the mission, design it, and build it, takes a very long time, and a major bite of years out of the scientific careers of those responsible. My hat's off to 'em. Contrast that to *any* politician, I dare ya. ;^)
Not only the tech but the math to compute these missions is amazing for someone like me who is totally Calculus challenged.