GVCALC(1)



NAME

     gvcalc  -  calculation of velocity from sets of MDI  filter-
     grams taken through a heliostat


SYNOPSIS

     gvcalc [-qvrf] [argument= value ...]


DESCRIPTION

     gvcalc calculates Dopplergrams from sets of MDI  filtergrams
     taken through the heliostat ground testing system.  The fil-
     tergrams are assumed presnt in  groups  of  five  at  tuning
     positions  0  through 4 (nominal continuum, -120 mA, -40 mA,
     +40 mA, +120 mA from  filter  transmission  center,  respec-
     tively).   The location of the image center is found for the
     individual filtergrams using the limb finder fit_limb()  and
     the  average  and  rms  center is saved.  The images are not
     registered prior to  the  doppler  shift  calculation.   The
     Doppler velocity is computed using the mdi_vcalc() function.
     The resulting image is inverted unless the no-flip flag (-f)
     is  given.   The  position  angle  is  computed based on the
     observation  time  and  date  but  the  Dopplergram  is  not
     rotated.   The  determined  radius  is used to differentiate
     full disk from calmode and high-res images.  If the image is
     determined  to  be  a  full  disk  measurement a calibration
     Doppler image is subtracted.  If the raw flag (-r) is given,
     the  calibration  image  is not subtracted and the ephemeris
     corrections (subtraction of Earth's spin and orbital motion)
     are not made.

     The -q option prints out the list of required arguments  and
     their  default  or environmental values, then quits.  The -v
     option sets verbose mode, redirecting history from stdout to
     stderr.


OPTIONS

     in0=name            dataset of filtergrams at  tuning  posi-
                         tion 0 (no default)

     in1=name            dataset of filtergrams at  tuning  posi-
                         tion 1 (no default)

     in2=name            dataset of filtergrams at  tuning  posi-
                         tion 2 (no default)

     in3=name            dataset of filtergrams at  tuning  posi-
                         tion 3 (no default)

     in4=name            dataset of filtergrams at  tuning  posi-
                         tion 4 (no default)

     outlog=name         name    of    log     file     (default:
                         /home/soi/data/logs/V_mdi.log)

     out=name            output dataset (default: Vobs.fits)

     calib=name          calibration      dataset       (default:
                         /home/soi/calib/calib.256.fits)

     vtable=name         velocity    lookup    table    (default:
                         /home/soi/tables/VTable.fits)

     frac_lenside=Real   parameter  for  limb  finding  (default:
                         70/1024)

     frac_box=Real       parameter  for  limb  finding  (default:
                         200/1024)

     frac_thresh=Real    parameter  for  limb  finding  (default:
                         0.3)


KEYWORDS

     The following keywords are set in the output file:

     GVCALC_VERS         Current gvcalc version.

     VTABLE_VERS         VTable used in Doppler velocity calcula-
                         tion.

     VRES                Velocity resolution in m/s.

     ISFLIPT             Boolean true if  image  flipped  top  to
                         bottom.

     X0                  Location of image center in pixels.

     Y0                  Location of image center in pixels.

     X0_RMS              Standard  deviation  of   image   center
                         determination.

     Y0_RMS              Standard  deviation  of   image   center
                         determination.

     RMAJOR              Determined image radius in pixels.

     R_RMS               Standard deviation of image radius.

     P                   P-angle to rotate image CW for N at top,
                         E to left.

     B0                  Latitude of sub-earth point.

     V_ORBIT             Line-of-sight velocity of MDI.

     IMAGE_T             Time of image observation.
     MDI_PATH            FullDisk or HighRes indicator.

     MDI_DATA            Observable indicator == "Doppler".

     CALIBFN             Calibration file path.

     VTABLE_NAME         Velocity lookup table filename.

     LOGFN               Log file name.

     MDI_MODE            Image or cal mode indicator, "Image"  or
                         "Calib".


EXAMPLES


FILES

     /home/soi/tables/VTable.fits


SEE ALSO

     fit_limb(3), mdi_vcalc(3)


DIAGNOSTICS


BUGS

     It would be a lot more convenient  to  have  the  associated
     filtergrams collected in a single dataset.

     The parameters used by the limb finder should not have to be
     set as arguments.

     Standard library IO functions are used to create output log.
     The  name  of  the output log file should be determined from
     the input data; without a default.

     The calib image to be subtracted is only correct for 256x256
     images.

     There is no correct recognition of High-Res images.


AUTHORS

     Phil Scherrer, Rick Bogart, Kay  Leibrand,  Luiz  Sa,  Katie
     Scott


HISTORY

     1994-02-14     SOI Version 0.8