SUBROUTINE VPOLVF
*
*  Module Number: 15.12.4
*
*  Module Name: polverify
*
*  Keyphrase:
*  ----------
*  Verify polarization calibrations of polarization efficiency and position
*  angle offset
*
*  Description:
*  ------------
*  This module verifies polarization and its position angle of targets for
*  any number of apertures (up to 20).
*  The polarization and its position angle of a target at a given aperture is
*  calculated from measurements at three different roll angles.
*  The distribution of roll angles should be such that they cover more than
*  90 degrees.  Ideally, they should be 60 degrees from one another.
*  For the same aperture, more than one measurements may be taken at the same
*  roll angle.  Also, for the same aperture, input data must have the same
*  target, and roughly obtained at the same temperature/epoch.
*  Maximum number of input data points is 2000.
*
*  FORTRAN Name: VPOLVF.FOR
*
*  Keywords of Accessed Files and Tables:
*  --------------------------------------
*  Name                         I/O     Description / Comments
*
*  Subroutines Called:
*  -------------------
*  CDBS:
*       CDPGT, VPVFBN, VPVFPT
*  SDAS:
*       UMSPUT
*  OTHERS:
*       none
*
*  History:
*  --------
*  Version      Date        Author          Description
*     1       07-15-86     J.-C. Hsu        Design and coding
*     2       10-05-87     J.-C. Hsu        F77 standard
*-------------------------------------------------------------------------------
*
*== local:
*                                       --count rate
        REAL                    CNT(2000),
*                                       --count rate's standard deviation
     :                          CNTSD(2000),
*                                       --observed and reference polarization
     :                          POL(20), P0(20),
*                                       --observed and reference position angle
     :                          PA(20), PA0(20),
*                                       --intensity
     :                          INTEN(20),
*                                       --temperature
     :                          TEMP(2000),
*                                       --mean temperature
     :                          TMPAVE(20),
*                                       --position angle of aperture used
     :                          APPA(2000)
*                                       --epoch
        DOUBLE PRECISION        EPOCH(2000),
*                                       --mean epoch
     :                          EPAVE(20)
*                                       --number of input data points
        INTEGER                 NPTS,
*                                       --number of apertures
     :                          NROWS,
*                                       --return status
     :                          STATUS, STATOK
*                                       --aperture
        CHARACTER*10            APERT(2000)
*                                       --target name
        CHARACTER*20            TARGET(2000)
*                                       --output table name
        CHARACTER*128           OFILE
*                                       --error message context
        CHARACTER*130           CONTXT
*=========================begin hsp.inc=========================================
*                                       --status return code
        INTEGER         OK, ERRNUM(20)
*                                       --message destination and priority
        INTEGER         DEST, PRIO
        DATA OK /0/
        DATA ERRNUM /701, 702, 703, 704, 705, 706, 707, 708, 709, 710,
     :               711, 712, 713, 714, 715, 716, 717, 718, 719, 720/
        DATA DEST, PRIO /1, 0/
*=========================end hsp.inc===========================================
*-------------------------------------------------------------------------------
*
*  read parameters and input data
*
        CALL CDPGT (
     :                  CNT, CNTSD, APPA, TEMP, EPOCH, APERT, TARGET,
     :                  NPTS, OFILE, STATUS)
        IF (STATUS .NE. OK) THEN
            CONTXT = 'error getting parameters and/or data'
            GO TO 999
        END IF
*
*  sort input data based on aperture/roll angle, calculate Stokes parameters for
*  each aperture
*
        CALL VPVFBN (CNT, CNTSD, APPA, TEMP, EPOCH, NPTS,
     :                  APERT, TARGET,
     :                  POL, PA, INTEN, P0, PA0, TMPAVE, EPAVE, NROWS,
     :                  STATUS)
        IF (STATUS .NE. OK) GO TO 1000
*
*  write result to output table
*
        CALL VPVFPT (OFILE, APERT, POL, PA, INTEN, P0, PA0,
     :                  TMPAVE, EPAVE, TARGET, NROWS,   STATUS)
        IF (STATUS .NE. OK) GO TO 1000
*
        STATUS = OK
        GO TO 1000
*
  999   CALL UMSPUT ('VPOLVF: ' // CONTXT, DEST, PRIO,   STATOK)
*
 1000   RETURN
        END