; docformat = 'rst'
;
; NAME:
;    genoidOpenObs
; PURPOSE:
;    Open a file, print a VOTable header for Genoid, and return the file unit
;+
; :Description:
;    Open a file, print a VOTable header for Genoid, and return the file unit
;
; :Categories:
;    Disk I/O, Genoid
;    
; :Params:
;    file: in, required, type=string
;        The path to the file to be opened
;    nRow: in, optional, type=integer
;        Number of epochs to be subsequently added to the file
;    system: in, required, type=string
;        Name of the dynamical system
;    target: in, required, type=string
;        NAme of the target
;
; :Returns: The file unit to be subsequently use to fill the file.
;
; :Author:
;    B.Carry (OCA)
;
; :History:
;    Change History::
;      Written in July 2013, B. Carry (IMCCE)
;      2013 Sep. - B.Carry (IMCCE) - Allow unknown number of row
;      2017 Apr. - B.Carry (OCA) - Updated to new Genoid XML structure
;      2018 Nov - B. Carry (OCA) - Changed VOTable structure
;      2019 Aug - B. Carry (OCA) - Updated FIELD items
;-
function genoidOpenObs, file, nRow, system, target
  COMPILE_OPT hidden, idl2
;-----------------------------------------------------------------------------------------------;
;-----------------------------------------------------------------------------------------------;
;---  TAG ---    I -- Initialization And Input Verification              -----------------------;
;-----------------------------------------------------------------------------------------------;
;-----------------------------------------------------------------------------------------------;
 ;--I.1-- Syntax Validation  -------------------------------------------------------------------;
  if not keyword_set(file) or not keyword_Set(system) or not keyword_set(target) then begin
    message, /ioError, 'Syntax: obs = genoidOpenObs( file, nRow, system, target )'
    return, -1
  endif

 ;--I.2-- Open Unit File for Writing  ----------------------------------------------------------;
  openW, unit, file, /Get_Lun


;-----------------------------------------------------------------------------------------------;
;-----------------------------------------------------------------------------------------------;
;---  TAG ---   II -- Write XML Preambule                                -----------------------;
;-----------------------------------------------------------------------------------------------;
;-----------------------------------------------------------------------------------------------;
 ;--II.1-- General XML VO Table Header  --------------------------------------------------------;
  printf, unit, '<?xml version="1.0" encoding="UTF-8"?>'
  printf, unit, '<vot:VOTABLE version="1.3" xsi:schemaLocation="http://www.ivoa.net/xml/VOTable/v1.3 http://www.ivoa.net/xml/VOTable/VOTable-1.3.xsd" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:vot="http://www.ivoa.net/xml/VOTable/v1.3" xmlns:stc="http://www.ivoa.net/xml/STC">'
  printf, unit, '  <vot:COOSYS ID="ICRS" system="ICRS" equinox="J2000"/>'
  printf, unit, '  <vot:INFO ID="status" name="QUERY_STATUS" value="OK"/>'
  printf, unit, '  <vot:INFO ID="supplier" name="Supplier" value="Provided by IMCCE/OBSPM/CNRS"/>'
  printf, unit, '  <vot:RESOURCE>'
  printf, unit, '    <vot:PARAM ID="ref_system" name="ref_system" datatype="char" arraysize="*" ucd="meta.note" value="'+strTrim(system,2)+'">'
  printf, unit, '      <vot:DESCRIPTION>Designation of the reference system</vot:DESCRIPTION>'
  printf, unit, '    </vot:PARAM>'
  printf, unit, '    <vot:PARAM ID="obs_target" name="obs_target" datatype="char" arraysize="*" ucd="meta.note" value="'+strTrim(target,2)+'">'
  printf, unit, '      <vot:DESCRIPTION>Designation of the observed target</vot:DESCRIPTION>'
  printf, unit, '    </vot:PARAM>'

 ;--II.2-- Number of Epochs  -------------------------------------------------------------------;
  if keyword_set(nRow) then begin
     printf, unit, '    <vot:TABLE name="obs.dat" nrows="'+strTrim(string(nRow,format='(I)'),2)+'">' 
  endif else printf, unit, '    <vot:TABLE name="obs.dat" nrows="<NROW>">'


;-----------------------------------------------------------------------------------------------;
;-----------------------------------------------------------------------------------------------;
;---  TAG ---  III -- Describe VOTable Fields                            -----------------------;
;-----------------------------------------------------------------------------------------------;
;-----------------------------------------------------------------------------------------------;
  printf, unit, '      <vot:FIELD ID="tjj" name="tjj" datatype="double" unit="d" ucd="time.epoch">'
  printf, unit, '        <vot:DESCRIPTION>Epoch of observation in Julian day</vot:DESCRIPTION>'
  printf, unit, '      </vot:FIELD>'
  printf, unit, '      <vot:FIELD ID="tiso" name="tiso" datatype="char" arraysize="*" unit="d" ucd="time.epoch">'
  printf, unit, '        <vot:DESCRIPTION>Epoch of observation in ISO format</vot:DESCRIPTION>'
  printf, unit, '      </vot:FIELD>'
  printf, unit, '      <vot:FIELD ID="ref_name" name="ref_name" datatype="char" arraysize="*" ucd="meta.note">'
  printf, unit, '        <vot:DESCRIPTION>Name of the observed target</vot:DESCRIPTION>'
  printf, unit, '      </vot:FIELD>'
  printf, unit, '      <vot:FIELD ID="xobs" name="xobs" datatype="double" unit="arcsec" ucd="pos.cartesian.x;obs" ref="ICRS">'
  printf, unit, '        <vot:DESCRIPTION>Observed x coordinates</vot:DESCRIPTION>'
  printf, unit, '      </vot:FIELD>'
  printf, unit, '      <vot:FIELD ID="yobs" name="yobs" datatype="double" unit="arcsec" ucd="pos.cartesian.y;obs" ref="ICRS">'
  printf, unit, '        <vot:DESCRIPTION>Observed y coordinates</vot:DESCRIPTION>'
  printf, unit, '      </vot:FIELD>'
  printf, unit, '      <vot:FIELD ID="xobs_err" name="xobs_err" datatype="double" unit="arcsec" ucd="stat.error;pos.cartesian.x;obs" ref="ICRS">'
  printf, unit, '        <vot:DESCRIPTION>Uncertainty of xobs coordinate</vot:DESCRIPTION>'
  printf, unit, '      </vot:FIELD>'
  printf, unit, '      <vot:FIELD ID="yobs_err" name="yobs_err" datatype="double" unit="arcsec" ucd="stat.error;pos.cartesian.y;obs" ref="ICRS">'
  printf, unit, '        <vot:DESCRIPTION>Uncertainty of yobs coordinate</vot:DESCRIPTION>'
  printf, unit, '      </vot:FIELD>'
  printf, unit, '      <vot:FIELD ID="xcalc" name="xcalc" datatype="double" unit="arcsec" ucd="pos.cartesian.x;meta.modelled" ref="ICRS">'
  printf, unit, '        <vot:DESCRIPTION>Computed x coordinates</vot:DESCRIPTION>'
  printf, unit, '      </vot:FIELD>'
  printf, unit, '      <vot:FIELD ID="ycalc" name="ycalc" datatype="double" unit="arcsec" ucd="pos.cartesian.y;meta.modelled" ref="ICRS">'
  printf, unit, '        <vot:DESCRIPTION>Computed y coordinates</vot:DESCRIPTION>'
  printf, unit, '      </vot:FIELD>'
  printf, unit, '      <vot:FIELD ID="xomc" name="xomc" datatype="double" unit="arcsec" ucd="stat.error;pos.cartesian.x;meta.modelled" ref="ICRS">'
  printf, unit, '        <vot:DESCRIPTION>Observed minus computed x position (xobs-xcalc)</vot:DESCRIPTION>'
  printf, unit, '      </vot:FIELD>'
  printf, unit, '      <vot:FIELD ID="yomc" name="yomc" datatype="double" unit="arcsec" ucd="stat.error;pos.cartesian.y;meta.modelled" ref="ICRS">'
  printf, unit, '        <vot:DESCRIPTION>Observed minus computed y position (yobs-ycalc)</vot:DESCRIPTION>'
  printf, unit, '      </vot:FIELD>'
  printf, unit, '      <vot:FIELD ID="timescale" name="timescale" datatype="char" arraysize="*" ucd="meta.note">'
  printf, unit, '        <vot:DESCRIPTION>Time scale of observation (UTC, TT)</vot:DESCRIPTION>'
  printf, unit, '      </vot:FIELD>'
  printf, unit, '      <vot:FIELD ID="centerframe" name="centerframe" datatype="char" arraysize="*" ucd="meta.note">'
  printf, unit, '        <vot:DESCRIPTION>Center of the reference frame (1:heliocentric, 2:geocentric, 3:topocentric, 4:spacecraft)</vot:DESCRIPTION>'
  printf, unit, '      </vot:FIELD>'
  printf, unit, '      <vot:FIELD ID="typeframe" name="typeframe" datatype="char" arraysize="*" ucd="meta.note">'
  printf, unit, '        <vot:DESCRIPTION>Type of frame (1:astrometric J2000, 2:apparent, 3:mean of date, 4:mean J2000)</vot:DESCRIPTION>'
  printf, unit, '      </vot:FIELD>'
  printf, unit, '      <vot:FIELD ID="coordtype" name="coordtype" datatype="char" arraysize="*" ucd="meta.note">'
  printf, unit, '        <vot:DESCRIPTION>Type of coordinates (1:spherical, 2:rectangular)</vot:DESCRIPTION>'
  printf, unit, '      </vot:FIELD>'
  printf, unit, '      <vot:FIELD ID="refframe" name="refframe" datatype="char" arraysize="*" ucd="meta.note">'
  printf, unit, '        <vot:DESCRIPTION>Reference plane (1:equator, 2:ecliptic)</vot:DESCRIPTION>'
  printf, unit, '      </vot:FIELD>'
  printf, unit, '      <vot:FIELD ID="obsuai" name="obsuai" datatype="char" arraysize="*" ucd="meta.note">'
  printf, unit, '        <vot:DESCRIPTION>Observatory IAU code</vot:DESCRIPTION>'
  printf, unit, '      </vot:FIELD>'
  printf, unit, '      <vot:FIELD ID="photom" name="photom" datatype="char" arraysize="*" ucd="phot.flux;meta.note">'
  printf, unit, '        <vot:DESCRIPTION>Photometric method used to obtain x,y measurements</vot:DESCRIPTION>'
  printf, unit, '      </vot:FIELD>'
  printf, unit, '      <vot:FIELD ID="dmag" name="dmag" datatype="double" unit="mag" ucd="phot.mag;em.opt.R;arith.diff">'
  printf, unit, '        <vot:DESCRIPTION>Difference in magnitude between primary and satellite</vot:DESCRIPTION>'
  printf, unit, '      </vot:FIELD>'
  printf, unit, '      <vot:FIELD ID="sigdmag" name="sigdmag" datatype="double" unit="mag" ucd="stat.stdev;phot.mag;em.opt.R">'
  printf, unit, '        <vot:DESCRIPTION>Standard deviation on dmag</vot:DESCRIPTION>'
  printf, unit, '      </vot:FIELD>'
  printf, unit, '      <vot:FIELD ID="quality" name="quality" datatype="char" arraysize="*" ucd="meta.note">'
  printf, unit, '        <vot:DESCRIPTION>Quality note of the measure (A|A+|B|C|D)</vot:DESCRIPTION>'
  printf, unit, '      </vot:FIELD>'
  printf, unit, '      <vot:FIELD ID="telescope" name="telescope" datatype="char" arraysize="*" ucd="meta.note">'
  printf, unit, '        <vot:DESCRIPTION>Telescope used to acquire the measure</vot:DESCRIPTION>'
  printf, unit, '      </vot:FIELD>'
  printf, unit, '      <vot:FIELD ID="camera" name="camera" datatype="char" arraysize="*" ucd="meta.note">'
  printf, unit, '        <vot:DESCRIPTION>Camera used to acquire the measure</vot:DESCRIPTION>'
  printf, unit, '      </vot:FIELD>'
  printf, unit, '      <vot:FIELD ID="filter" name="filter" datatype="char" arraysize="*" ucd="meta.note">'
  printf, unit, '        <vot:DESCRIPTION>Filter used to acquire the measure</vot:DESCRIPTION>'
  printf, unit, '      </vot:FIELD>'
  printf, unit, '      <vot:FIELD ID="author" name="author" datatype="char" arraysize="*" ucd="meta.note">'
  printf, unit, '        <vot:DESCRIPTION>Name of the person who measured the image</vot:DESCRIPTION>'
  printf, unit, '      </vot:FIELD>'
  printf, unit, '      <vot:FIELD ID="when" name="when" datatype="char" arraysize="*" ucd="meta.note">'
  printf, unit, '        <vot:DESCRIPTION>Epoch at which the image was measured the last time (ISO format)</vot:DESCRIPTION>'
  printf, unit, '      </vot:FIELD>'
  printf, unit, '      <vot:FIELD ID="bibitem" name="bibitem" datatype="char" arraysize="*" ucd="meta.note">'
  printf, unit, '        <vot:DESCRIPTION>Bibliographic reference</vot:DESCRIPTION>'
  printf, unit, '      </vot:FIELD>'
  printf, unit, '      <vot:DATA>'
  printf, unit, '        <vot:TABLEDATA>'



;-----------------------------------------------------------------------------------------------;
;-----------------------------------------------------------------------------------------------;
;---  TAG ---   IV -- Return the File Logical Unit                       -----------------------;
;-----------------------------------------------------------------------------------------------;
;-----------------------------------------------------------------------------------------------;
  return, unit

end