; from nsx.c
; Return an empty AVP structure

function avptype
  common nsx 
; NIRES Calibration Parameter for each echelle order.
  AVPstructure = { $
                 xoff: dblarr(MAXSP),$   ;        /* xoff value for each column of AVP[nso] */
                 coef: dblarr(MAXSP,3),$ ;     /* coeffecients (order=2) for each column of AVP[nso] */
                 xoffinv: dblarr(MAXSP),$ ;     /* inverse xoff value for each column of AVP[nso] */
                 coefinv: dblarr(MAXSP,3)$ ;  /* inverse coeffecients (order=2) for each column of AVP[nso] */
                 }

  return, AVPstructure

end