[jandrese]

If you are clever with cabling through your shade and launch in the right orbit you can use the Earths magnetic field to keep the things oriented properly. Astronomers would hate you though.

I'd guess it would be far more efficient to launch more of these into regular orbit than trying to assemble them out in L1 and keep them from drifting off, even though you would need to launch at least twice as many for the same amount of coverage.