Microshutter Array System for James Webb Space Telescope

The invention concerns a levelling device (10) for an impact roller of the type having at least one out-of-round compactor mass which, when caused to traverse a soil surface, applies periodic compacting blows to that surface. The levelling device of the invention is coupled to the impact roller so as to trail behind the impact roller. It includes a support frame (36) and, for each compactor mass of the impact roller, a ground-engaging levelling blade (52) fast with the support frame. The levelling blade is arranged to cut soil which has been traversed by the compactor mass and thereby to perform a soil levelling action. A ground-engaging shoe (58), one for each levelling blade, is connected to the support frame for pivotal movement about an axis transverse to the direction of movement of the impact roller The shoe serves to control the depth of cut achieved by the levelling blade.