The TechCrunch article NASA details Deep Space Atomic Clock and other tests launching on SpaceX Falcon Heavy says:
Jill Seubert, Deep Space Navigator for NASA, explained that this is the world’s first ion-based atomic space clock. “It’s about 50 times more stable than the GPS atomic clocks we use,” adding that we currently have to navigate from Earth because the clocks on board spacecraft are really not very good at maintaining time accuracy.
and then later says:
That will enable one-way tracking, when paired with data gathered by an onboard camera, using a signal from Earth to the spacecraft, or from the spacecraft to Earth, but with no round-trip needed. This allows for more efficient tracking across all flights, because you do less time sharing with an existing deep space network. It also enables “self-driving spacecraft,” as Seubert put it, which requires no direction at all from navigators on earth. (emphasis added)
Question: Exactly how does an atomic clock facilitate a “self-driving spacecraft” when paired with an onboard camera?
Is it still necessary to pick up a beacon time signal from Earth? What exactly is the camera for?