grvdef Subroutine

 TJD    = TDB JULIAN DATE OF OBSERVATION
 LOC    = CODE FOR LOCATION OF OBSERVER, DETERMINING
          WHETHER THE GRAVITATIONAL DEFLECTION DUE TO THE
          EARTH ITSELF IS APPLIED (IN)
          SET LOC=0 FOR NO EARTH DEFLECTION (NORMALLY MEANS
                    OBSERVER IS AT GEOCENTER)
          SET LOC=1 TO ADD IN EARTH DEFLECTION (NORMALLY
                    MEANS OBSERVER IS ON OR ABOVE SURFACE
                    OF EARTH, INCLUDING EARTH ORBIT)
 POS1   = POSITION VECTOR OF OBSERVED OBJECT, WITH RESPECT TO
          ORIGIN AT OBSERVER (OR THE GEOCENTER), REFERRED
          TO ICRS AXES, COMPONENTS IN AU (IN)
 POBS   = POSITION VECTOR OF OBSERVER (OR THE GEOCENTER),
          WITH RESPECT TO ORIGIN AT SOLAR SYSTEM BARYCENTER,
          REFERRED TO ICRS AXES, COMPONENTS IN AU (IN)
 POS2   = POSITION VECTOR OF OBSERVED OBJECT, WITH RESPECT TO
          ORIGIN AT OBSERVER (OR THE GEOCENTER), REFERRED
          TO ICRS AXES, CORRECTED FOR GRAVITATIONAL
          DEFLECTION, COMPONENTS IN AU (OUT)