Closest and furthest pairs of unmanned space craft Options

[tasp]

Ok, obviously, furthest separation of spacecraft would be Pioneer 10 and depending on when we check, Pioneer 11, and later Voyager 1 and/or Voyager 2.

But what is the closest 2 craft have come on seperate missions ??

Were there any close approaches of Magellan to any Soviet orbiters at Venus ??

Has there any been a Soviet Lander on Mars close to either Viking ?? Any chance of the Halley armada vehicles being particularly close to each other during their missions ??


I would mostly be interested in active mission encountering each other, but a live mission 'checking out' a prior 'dead' one closely (Apollo 12 and Surveyor 3 type encounter for example, but keep in mind Apollo 12 was manned and not applicable here) would be interesting too.

[ElkGroveDan]

After the Lunar Surveyors (1 & 3) and Soviet Luna (16 & 20?), I'd say Viking 1 and 2. Of course if you are talking about any two craft as opposed to matched pairs, then on Mars it would be Viking 1 and Pathfinder

(Assuming we exclude possible classified ASAT touch and go encounters in Earth orbit.)