1/4 g but that includes a capacitor. Still, it might be able to send at least 1 or 2 pixels back.

But the launch energy required makes the whole thing bonkers. 100 GW focused laser energy? That's 100,000x more than what came out of Ronnie Raygun's wettest SDI dreams. Anything between the sail and the laser will go *poof*.

(Now, if they could work on a flux capacitor instead, 100 GW would power 80 time traveling De Loreans...)