[russholmes]

The Rayleigh limit in spatial resolution of an image forming device is given by:

l = 1.22 * λ * L / D

Where λ is wavelength, L is distance and D is optical element diameter.

For satellite at an altitude of 150 km with 2.4 m diameter mirror and 0.4 μm blue light, this gives a spatial resolution of 0.3 m. To read a number plate requires an order of magnitude better than this.

[ISL]

Thus an interferometric imaging system can theoretically do it ( two input scopes separated by 24m). The hard part is the atmosphere.

[russholmes]

In one axis, and I don't think they were capable of doing it at the time suggested.