This is another mat board model. The design starts as a cube. The faces of the cube are divided as shown on the right. All vertices are pushed out so that they are the same distance from the center of the cube as the outside corners. After the angels and the strut lengths are calculated there only remains the strut design.

This model could have been made with straight struts.

The model could have been made spherical by cutting the struts curved, so that they are segments of a circle the same radius as the center of the cube is to the outside corner.

The model was made with that curvature reversed making the struts concaved. This gives a scalloped effect.

For more info on the math and a great way to get started in this type of model I recommend buying “Spherical Models” by Magnus Wenninger.