  The bianisotropic susceptibility Generalized Sheet Transition Conditions
(GSTCs) synthesis method is extended from planar to spherical metasurfaces.
Properties specific to the non-zero intrinsic curvature of the spherical shape
are highlighted and different types of corresponding transformations are
described. Finally, the susceptibility-GSTC method and exotic properties of
spherical metasurfaces are validated and illustrated with three examples:
illusion transformation, ring focusing and birefringence.
