On a related note, does anyone know if it is possible/how hard it is to get an accurate read on a handful of stars/pulsar in all weather/light conditions using a radio telescope? Or indeed what the state of the art is on "passive" computer/database assisted navigation?

I'd imagine with high accuracy clocks, much and high-precision information on celestial bodies, there should've been some advancements in this area? Or will the resolution (due to atmospheric effects etc) be too low for it to be useful?