by the finite speed of light:  one needs to point
   to where the target appears to be as opposed to where it actually
   is at the epoch of observation. We use the adjectives
   &quot;geometric,&quot; &quot;uncorrected,&quot; or &quot;true&quot; to refer to an actual
   position or state of a target at a specified epoch. When a
   geometric position or state vector is modified to reflect how it
   appears to an observer, we describe that vector by any of the
   terms &quot;apparent,&quot; &quot;corrected,&