The article does compare the resolution required, the 0.05 picometer, not to the diameter of an atom but to the diameter of the nucleus of an atom.

The resolution is about (within an order of magnitude - x10) what I got in some thesis experiments as a student, but I didn't have to stand quite 5 million km from what I was measuring.

The actual instrument design, construction, and deployment is obviously more of an engineering challenge than pure science. The "science" is understood, and the article gives some (very elementary) hints at the scientific justifications and explanations for it all.

John