The wave-equation angle-domain Hessian can be computed from the subsurface offset wave-equation Hessian via an angle-to-offset transformation following the approach presented by Fomel (2004).
The Hessian computation in a model with a single reflector under a Gaussian velocity anomaly shows that the angle dimension lacks of resolution to be able to interpret which angles get more illumination. The interpretation and improvement of resolution of the angle Hessian topics of future research.