Det viser sig, at de ikke har simulatorer på jorden pga Voyagers alder:

Newer NASA missions have hardware and software simulators on the ground, where engineers can test new procedures to make sure they do no harm when they uplink commands to the real spacecraft. Due to its age, Voyager doesn’t have any ground simulators, and much of the mission’s original design documentation remains in paper form and hasn’t been digitized.

Fra denne fascinerende artikel i Wired: https://www.wired.com/story/nasa-repair-voyager-1-spacecraft-data/