Centauri Dreams discusses a DNA-based self-replicating interstellar probe:
Think of a probe that gets around the payload mass problem by using molecular processes to create cameras and imaging systems not by mechanical nanotech but by inherently biological methods.
A Von Neumann self-replicating probe comes to mind, but we may not have to go to that level in our earliest iterations. The biggest challenge to our interstellar ambitions is propulsion, with the need to push a payload sufficient to conduct a science mission to speeds up to an appreciable percentage of lightspeed. The more we reduce payload size, the more feasible some missions become
This is similar to Robert L. Forward‘s starwisp concept (popularised by Charlie Stross in Accelerando).
I suspect that if and when we do get round to interstellar exploration it will involve sending small-mass packages that are capable of bootstrapping themselves to a broadcast/exploration mode using local materials on arrival in the target system.
It remains to be seen what kind of space-based molecular replicating systems become viable. Will we be able to create space-hardened bioware, or good ol’ fashioned machine phase fullerene nanotech?