According to the WESTPAC Satellite Scientific-Technical Note for User document, a single cube contributes to the return. The radius of the satellite taken through the front face of the cubes is 91mm, the height of the cubes 18.9mm, and the refractive index at 532nm as 1.4607. Therefore, for a green pulse at normal incidence, the distance DeltaR to the CoM is [91.0 - (18.9 * 1.4607)] = 63.4mm For an incidence angle of 20 degrees, which is near the maximum possible for the shields, the correction changes by only 0.7mm, to 64.1mm.