When we are considering L/S and U/S, we should remember the advantages of U/V and V/U. The original choice of U/V for phase 3 satellites allowed for an antenna that would provide 75% orbit coverage. Path loss for L and S is much higher so AO13 and AO-40 had much narrower beams and covered less of the orbit in those modes. So, in addition to the fact that S will be unavailable in many areas due to noise levels that are 20+ dB higher today, the time available in those areas for this mode is much less than for U/V or V/U. The attached document provides a graphical comparison of U and L uplink antenna coverage for the same ground station radiated power level. The V and S downlinks are very similar.