Cusped envelope of the wave fronts emanating from a uniformly rotating source point whose linear speed exceeds the speed of light, c. (a) Three-dimensional view of the two-sheeted envelope of wave fronts emanating from a volume element of the current sheet. This envelope spirals into the far zone, maintaining a symmetry with respect to the plane of the orbit of the source element. (b) Cusp locus along which the two sheets of the envelope meet. This curve tangentially touches the light cylinder where it crosses the plane of the orbit and spirals into the far zone on a hyperboloid whose asymptotes lie on the cones θ_P = arcsin[c/(r_Sω)] and θ_P = π − arcsin[c/(r_Sω)], where r_S is the radius of the circular orbit of the source element.