The rectangular section torus containing all the BeppoSAX orbits has been split into a grid of cells of coordinates ( ), ,...,360, ,...,8. Taking a fixed Km, i.e. the mean value of the range, an angular step , and a step Km, the resulting grid consists of cells, that can be approximated to parallelepipedal (nearly cubic) () Km blocks ( ).

Whenever the spacecraft is inside a given cell, its position is approximated
to the cell center, whose coordinates are expressed as follows:

The step between two adjacent cells ( 120 Km) subtends an angle Km) with respect to the Earth center; hence, the angular resolution of the sky portion which is calculated to be Earth-blocked is , when using such an orbit grid.