We basically know how to do this. STEREO used lunar gravity assist (check it out, very cool move) to visit Sun-Earth L4 and L5. On the other hand, Gaia was bas

We basically know how to do this. STEREO used lunar gravity assist (check it out, very cool move) to visit Sun-Earth L4 and L5. On the other hand, Gaia was basically the highest priority scientific mission of ESA and it took 20 years from proposal to launch...