ected epoch 
               et+lt: 
 
                  &quot;XLT&quot;      &quot;Transmission&quot; case:  correct for 
                             one-way light time using a Newtonian 
                             formulation. This correction yields the 
                             position of the target at the moment it 
                             receives photons emitted from the 
                             observer's location at `et'. 
 
                  &quot;XLT+S&quot;    &quot;Transmission&