Cassian can't see her which he knows is how she works but isn't ideal now. The lights are too bright and he doesn't want to be just sitting when the patrol returns.

He looks outside to see if there's a way he can disable the cannon and fires two sharp blasts at it. Not enough to take it fully down, this blaster isn't strong enough or equipped to fire that far but it should make their escape a little easier, "Doing our best not to die, Kay."