Are there anymore details known, like the resolution of the cameras or what size objects will be visible? With each dove covering 2 million km² per day (it says at the bottom) and capable of 200mbps downlink, one might get an upper bound of what resolution is feasible (with different compression techniques) but I am guessing the limiting factor is the camera.

And does each dove cover the same surface daily, or do they rotate around and get a different patch of the earth every day? Because in the former case, with diffs you could get amazing compression ratios, and I bet you can already get very far with very simple and fast algorithms.