SET_EPHEMERIS_KEYWORDS(3)

NAME

     append_MDI_data_comment,                   set_DPC_keywords,
     set_ephemeris_keywords,               set_imgscale_keywords,
     set_orientation_keywords - functions for  setting  essential
     ancillary information into MDI data files.

Syntax

     #include <MDI.h>

     void append_MDI_data_comment (img)
     void set_DPC_keywords (img, dpc)
     int set_ephemeris_keywords (img, t, tmod)
     int set_imgscale_keywords (img, t, code, obsdist)
     int set_orientation_keywords (img, t, dpc, offset, xc, yc, tmod)

     SDS *img;
     struct DPC dpc;
     TIME t, *tmod;
     double obsdist, xc, yc;
     unsigned int code, offset;

DESCRIPTION

     These functions all add certain  standard  calibrating  key-
     words  or  other  information to MDI data images or records,
     based on observing time and certain  other  required  confi-
     guration information.

     append_MDI_data_comment merely adds certain comment lines to
     the FITS files containing the data.  These comments give the
     source of the data and a URL for additional  information  on
     data  rights, keyword definitions, data quality, etc.  It is
     a good idea to call it in any module  producing  export  MDI
     data  that  does  not  copy over the comments from its input
     data.  It is run from mdical, and the comments are automati-
     cally preserved at least through level 1.5.

     set_DPC_keywords sets  the  keywords:   DPC_OBSR,  DPC_FORM,
     DPC_CROP,  DPC_LIM0, DPC_LIM1, DPC_ORGN, DPC_RATE, DPC_SMPL,
     DPC_VERS, DPC_CONF, BUNIT, DATASIGN, and INTERVAL, based  on
     the  struct  corresponding  to a particular MDI data product
     code.


     set_ephemeris_keywords sets the keywords:  OBS_DIST, OBS_B0,
     OBS_L0, OBS_VR, OBS_VN, OBS_VW, R_SUN, and R_SOLAR, based on
     the observation time t and (for R_SUN and R_SOLAR) the image
     scale.  The appropriate image scale keywords are expected to
     already be in the data; if they are not found, the last  two
     keywords are not set.

     set_imgscale_keywords sets the keywords:  FD_SCALE,  HR_MAG,
     S_MAJOR,  S_MINOR,  S_ANGLE,  MAGNIFY,  IM_SCALE,  X_OPAXIS,
     Y_OPAXIS, PLATE_X, PLATE_Y, X_SCALE,  Y_SCALE,  XSCALE,  and
     YSCALE,  based on the observation time, the MDI data product
     code, and the SOHO-sun distance in AU. If  appropriate  key-
     words  for  any of the arguments are in the data header (DPC
     and either T_OBS or T_REF are all that are really necessary)
     the  corresponding argument values can be set to 0.  If they
     are non-zero they will over-ride the  corresponding  keyword
     values in the data.  The full-disc mode plate scale is table
     driven, based on observing time  and  a  polynomial  fit  in
     observing  distance.   A  fixed nominal value is supplied if
     the requested observing time is outside  the  range  of  the
     table,  which begins at 1995.12.21_12:00 UT.  This value can
     thus be forced by specifying an argument time  value  before
     the beginning of the table (but greater than 0!)  (As usual,
     time is assumed specified in seconds since the internal  SOI
     epoch  of  1977.01.01.)   The  other  non-nominal values are
     either DPC-driven or derived.

     set_orientation_keywords  sets  the   keywords:    X_OFFSET,
     Y_OFFSET,  MDI_X0,  MDI_Y0,  X0,  Y0,  XCEN,  YCEN, SOLAR_P,
     SOLAR_P0, and P_ANGLE, based on the  observation  time,  the
     DPC  struct, a binary code representing the subraster offset
     for certain data products, and optional override values  for
     xc  and/or  yc  (corresponding  to MDI_X0 and MDI_Y0 respec-
     tively).  If these values are not specified, values will  be
     supplied  from  either  the  smoothed  or  the  raw pointing
     tables, or a  nominal  value,  as  available,  in  order  of
     preference.   To use the best available tabulated or nominal
     values, xc (and/or yc) must be set equal  to  -32768.0.   As
     with  set_ephemeris_keywords,  appropriate  image scale key-
     words are expected to already be in the data;  but  if  they
     are not found they will be determined based on the observing
     time and DPC.  The offset code is only needed for sub-raster
     type data products.

DIAGNOSTICS

     set_imgscale_keywords returns the value returned by  a  call
     to   MDI_plate_scale_adjustment().    set_ephemeris_keywords
     returns the value returned by a  call  to  soho_ephemeris().
     set_orientation_keywords always returns 0.

BUGS

     The functions  described  here  put  extra  explanatory  and
     status information in the comment field of the relevant FITS
     header card images; this information is not propagated  when
     the  data  are  read and rewritten by most modules, however,
     due to a conceptual limitation (flaw)  in  the  vds  library
     approach to data record management.

     The ellipse and high-resolution field  magnification  values
     supplied  by  set_imgscale_keywords  are purely nominal.  So
     too   are   the   position-   angle   values   supplied   by
     set_orientation_keywords.

     Unlike    set_imgscale_keywords,    set_orientation_keywords
     requires  that the DPC and offset arguments be supplied; the
     function will not search for them in the data if necessary.

     Despite the names, these are highly MDI-specific functions.

FILES

     ~CM/tables/calib/geom/scale_corrections
     ~CM/tables/ephemeris/mdi_pointing.raw
     ~CM/tables/ephemeris/mdi_pointing.smooth
     ~CM/tables/ephemeris/eof/mdi_pointing.raw
     ~CM/tables/ephemeris/mdi_roll.raw
     ~CM/tables/ephemeris/summary
     ~CM/lib/libMDI.a
     ~CM/lib/libastro.a

AUTHOR

     Rick Bogart

HISTORY

     2001-02-27     SOI Version 4.8

SET_EPHEMERIS_KEYWORDS(3)

NAME

Syntax

DESCRIPTION

DIAGNOSTICS

BUGS

FILES

SEE ALSO

AUTHOR

HISTORY