KPL/FK

   MEX_NADIR_PY and MEX_NADIR_MY frames defined below implement the 
   nominal MEX nadir pointed orientation when the s/c flies +Y or -Y
   forward: 

      +Z        -- the geometric direction from MEX to the center of Mars

      +Y or -Y  -- as close as possible to the geometric velocity of MEX
                   wrt Mars in the Mars body-fixed frame

      +X        -- completes the right handed frame

   BVS/NAIF, 11/26/23. 

   \begindata

      FRAME_MEX_NADIR_PY          = -41931
      FRAME_-41931_NAME           = 'MEX_NADIR_PY'
      FRAME_-41931_CLASS          = 5
      FRAME_-41931_CLASS_ID       = -41931
      FRAME_-41931_CENTER         = -41
      FRAME_-41931_RELATIVE       = 'J2000'
      FRAME_-41931_DEF_STYLE      = 'PARAMETERIZED'
      FRAME_-41931_FAMILY         = 'TWO-VECTOR'
      FRAME_-41931_PRI_AXIS       = 'Z'
      FRAME_-41931_PRI_VECTOR_DEF = 'OBSERVER_TARGET_POSITION'
      FRAME_-41931_PRI_OBSERVER   = 'MARS EXPRESS'
      FRAME_-41931_PRI_TARGET     = 'MARS'
      FRAME_-41931_PRI_ABCORR     = 'NONE'
      FRAME_-41931_SEC_AXIS       = 'Y'
      FRAME_-41931_SEC_VECTOR_DEF = 'OBSERVER_TARGET_VELOCITY'
      FRAME_-41931_SEC_OBSERVER   = 'MARS'
      FRAME_-41931_SEC_TARGET     = 'MARS EXPRESS'
      FRAME_-41931_SEC_ABCORR     = 'NONE'
      FRAME_-41931_SEC_FRAME      = 'IAU_MARS'

      FRAME_MEX_NADIR_MY          = -41932
      FRAME_-41932_NAME           = 'MEX_NADIR_PY'
      FRAME_-41932_CLASS          = 5
      FRAME_-41932_CLASS_ID       = -41932
      FRAME_-41932_CENTER         = -41
      FRAME_-41932_RELATIVE       = 'J2000'
      FRAME_-41932_DEF_STYLE      = 'PARAMETERIZED'
      FRAME_-41932_FAMILY         = 'TWO-VECTOR'
      FRAME_-41932_PRI_AXIS       = 'Z'
      FRAME_-41932_PRI_VECTOR_DEF = 'OBSERVER_TARGET_POSITION'
      FRAME_-41932_PRI_OBSERVER   = 'MARS EXPRESS'
      FRAME_-41932_PRI_TARGET     = 'MARS'
      FRAME_-41932_PRI_ABCORR     = 'NONE'
      FRAME_-41932_SEC_AXIS       = '-Y'
      FRAME_-41932_SEC_VECTOR_DEF = 'OBSERVER_TARGET_VELOCITY'
      FRAME_-41932_SEC_OBSERVER   = 'MARS'
      FRAME_-41932_SEC_TARGET     = 'MARS EXPRESS'
      FRAME_-41932_SEC_ABCORR     = 'NONE'
      FRAME_-41932_SEC_FRAME      = 'IAU_MARS'

   \begintext

End of FK.