  Galaxy clusters are considered as excellent probes for cosmology. For that
purpose, their mass needs to be measured and their structural properties needs
to be understood. We propose a method for galaxy cluster mass reconstruction
which combines information from strong lensing, weak lensing shear and flexion.
We extend the weak lensing analysis to the inner parts of the cluster and, in
particular, improve the resolution of substructure. We use simulations to show
that the method recovers the mass density profiles of the cluster. We find that
the weak lensing flexion is sensitive to substructure. After combining the
flexion data into the joint weak and strong lensing analysis, we can resolve
the cluster properties with substructures.
