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         title="Permalink to Editing metadata in measurement sets">Editing metadata in measurement sets</a></h2>
 
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      2023/08/11
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      By <a class="url fn" href="https://keflavich.github.io/blog/author/adam-ginsburg-adamgginsburggmailcom.html">Adam Ginsburg (Adam.G.Ginsburg@gmail.com)</a>
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    <p>I needed to update the position of VLA phase calibrator <a class="reference external" href="http://simbad.u-strasbg.fr/simbad/sim-id?Ident=%402384864&amp;Name=QSO%20J1744-3116&amp;submit=submit">J1744-3116</a> in my measurement sets.  The VLA coordinate is:</p>
<blockquote>
<tt class="docutils literal">17:33:02.705790 <span class="pre">-13.04.49.54823</span> J2000</tt></blockquote>
<p>while the ALMA coordinate is</p>
<blockquote>
<tt class="docutils literal">17:44:23.578227 <span class="pre">-31.16.36.29204</span> ICRS</tt></blockquote>
<p>and the SIMBAD coordinate is</p>
<blockquote>
<tt class="docutils literal">17 44 23.57824 <span class="pre">-31</span> 16 36.2943 ICRS</tt></blockquote>
<p>These are separated by a significant amount:</p>
<div class="highlight"><pre><span></span><span class="kn">from</span> <span class="nn">astropy</span> <span class="kn">import</span> <span class="n">units</span> <span class="k">as</span> <span class="n">u</span><span class="p">,</span> <span class="n">coordinates</span>
<span class="kn">import</span> <span class="nn">numpy</span> <span class="k">as</span> <span class="nn">np</span>

<span class="n">vla_coord</span> <span class="o">=</span> <span class="n">coordinates</span><span class="o">.</span><span class="n">SkyCoord</span><span class="p">(</span><span class="s2">&quot;17:33:02.705790 -13:04:49.54823&quot;</span><span class="p">,</span> <span class="n">unit</span><span class="o">=</span><span class="p">(</span><span class="n">u</span><span class="o">.</span><span class="n">h</span><span class="p">,</span> <span class="n">u</span><span class="o">.</span><span class="n">deg</span><span class="p">),</span> <span class="n">frame</span><span class="o">=</span><span class="s1">&#39;fk5&#39;</span><span class="p">)</span>
<span class="n">alma_coord</span> <span class="o">=</span> <span class="n">coordinates</span><span class="o">.</span><span class="n">SkyCoord</span><span class="p">(</span><span class="s2">&quot;17:44:23.578227 -31:16:36.29204&quot;</span><span class="p">,</span> <span class="n">unit</span><span class="o">=</span><span class="p">(</span><span class="n">u</span><span class="o">.</span><span class="n">h</span><span class="p">,</span> <span class="n">u</span><span class="o">.</span><span class="n">deg</span><span class="p">),</span> <span class="n">frame</span><span class="o">=</span><span class="s1">&#39;icrs&#39;</span><span class="p">)</span>
<span class="n">simbad_coord</span> <span class="o">=</span> <span class="n">coordinates</span><span class="o">.</span><span class="n">SkyCoord</span><span class="p">(</span><span class="s1">&#39;17 44 23.57824 -31 16 36.2943&#39;</span><span class="p">,</span> <span class="n">unit</span><span class="o">=</span><span class="p">(</span><span class="n">u</span><span class="o">.</span><span class="n">h</span><span class="p">,</span> <span class="n">u</span><span class="o">.</span><span class="n">deg</span><span class="p">),</span> <span class="n">frame</span><span class="o">=</span><span class="s1">&#39;icrs&#39;</span><span class="p">)</span>

<span class="n">alma_coord</span><span class="o">.</span><span class="n">separation</span><span class="p">(</span><span class="n">vla_coord</span><span class="p">)</span><span class="o">.</span><span class="n">to</span><span class="p">(</span><span class="n">u</span><span class="o">.</span><span class="n">arcsec</span><span class="p">)</span>
<span class="c1"># &lt;Angle 0.28848595 arcsec&gt;</span>

<span class="n">simbad_coord</span><span class="o">.</span><span class="n">separation</span><span class="p">(</span><span class="n">vla_coord</span><span class="p">)</span><span class="o">.</span><span class="n">to</span><span class="p">(</span><span class="n">u</span><span class="o">.</span><span class="n">arcsec</span><span class="p">)</span>
<span class="c1"># &lt;Angle 0.29071513 arcsec&gt;</span>

<span class="n">simbad_coord</span><span class="o">.</span><span class="n">separation</span><span class="p">(</span><span class="n">alma_coord</span><span class="p">)</span><span class="o">.</span><span class="n">to</span><span class="p">(</span><span class="n">u</span><span class="o">.</span><span class="n">arcsec</span><span class="p">)</span>
<span class="c1"># &lt;Angle 0.00226614 arcsec&gt;</span>
</pre></div>
<p>This is caused by a typo in the VLA calibrator catalog (Lorant Sjouwerman, private communication).</p>
<p>To fix it:</p>
<div class="highlight"><pre><span></span><span class="n">tb</span><span class="o">.</span><span class="n">open</span><span class="p">(</span><span class="s1">&#39;22A-020.sb41257746.eb41788351.59700.31502699074/22A-020.sb41257746.eb41788351.59700.31502699074.ms/FIELD&#39;</span><span class="p">)</span>

<span class="c1"># get the existing PHASE_DIR.  Shape is [coordinates, ?, sourceID]</span>
<span class="n">phasedir</span> <span class="o">=</span> <span class="n">tb</span><span class="o">.</span><span class="n">getcol</span><span class="p">(</span><span class="s1">&#39;PHASE_DIR&#39;</span><span class="p">)</span>
<span class="c1"># figure out which row contains the to-be-modified source</span>
<span class="n">rownr</span> <span class="o">=</span> <span class="n">np</span><span class="o">.</span><span class="n">argmax</span><span class="p">(</span><span class="n">tb</span><span class="o">.</span><span class="n">getcol</span><span class="p">(</span><span class="s1">&#39;NAME&#39;</span><span class="p">)</span> <span class="o">==</span> <span class="s1">&#39;J1744-3116&#39;</span><span class="p">)</span>
<span class="c1"># modify the phasedir.  CASA expects coordinates to be wrapped at 180 deg</span>
<span class="n">phasedir</span><span class="p">[:,</span> <span class="mi">0</span><span class="p">,</span> <span class="n">rownr</span><span class="p">]</span> <span class="o">=</span> <span class="n">simbad_coord</span><span class="o">.</span><span class="n">fk5</span><span class="o">.</span><span class="n">ra</span><span class="o">.</span><span class="n">wrap_at</span><span class="p">(</span><span class="mi">180</span><span class="o">*</span><span class="n">u</span><span class="o">.</span><span class="n">deg</span><span class="p">)</span><span class="o">.</span><span class="n">rad</span><span class="p">,</span> <span class="n">simbad_coord</span><span class="o">.</span><span class="n">fk5</span><span class="o">.</span><span class="n">dec</span><span class="o">.</span><span class="n">rad</span>

<span class="kn">import</span> <span class="nn">shutil</span>
<span class="n">shutil</span><span class="o">.</span><span class="n">copytree</span><span class="p">(</span><span class="s1">&#39;22A-020.sb41257746.eb41788351.59700.31502699074/22A-020.sb41257746.eb41788351.59700.31502699074.ms/FIELD&#39;</span><span class="p">,</span> <span class="s1">&#39;22A-020.sb41257746.eb41788351.59700.31502699074/22A-020.sb41257746.eb41788351.59700.31502699074.ms/FIELD.backup&#39;</span><span class="p">)</span>
<span class="n">tb</span><span class="o">.</span><span class="n">open</span><span class="p">(</span><span class="s1">&#39;22A-020.sb41257746.eb41788351.59700.31502699074/22A-020.sb41257746.eb41788351.59700.31502699074.ms/FIELD&#39;</span><span class="p">,</span> <span class="n">nomodify</span><span class="o">=</span><span class="kc">False</span><span class="p">)</span>
<span class="n">tb</span><span class="o">.</span><span class="n">putcol</span><span class="p">(</span><span class="n">columnname</span><span class="o">=</span><span class="s1">&#39;PHASE_DIR&#39;</span><span class="p">,</span> <span class="n">value</span><span class="o">=</span><span class="n">phasedir</span><span class="p">)</span>
<span class="n">tb</span><span class="o">.</span><span class="n">flush</span><span class="p">()</span>
<span class="n">tb</span><span class="o">.</span><span class="n">close</span><span class="p">()</span>
</pre></div>
<p>Put all together:</p>
<div class="highlight"><pre><span></span><span class="kn">from</span> <span class="nn">astropy</span> <span class="kn">import</span> <span class="n">units</span> <span class="k">as</span> <span class="n">u</span><span class="p">,</span> <span class="n">coordinates</span>
<span class="kn">import</span> <span class="nn">numpy</span> <span class="k">as</span> <span class="nn">np</span>

<span class="n">simbad_coord</span> <span class="o">=</span> <span class="n">coordinates</span><span class="o">.</span><span class="n">SkyCoord</span><span class="p">(</span><span class="s1">&#39;17 44 23.57824 -31 16 36.2943&#39;</span><span class="p">,</span> <span class="n">unit</span><span class="o">=</span><span class="p">(</span><span class="n">u</span><span class="o">.</span><span class="n">h</span><span class="p">,</span> <span class="n">u</span><span class="o">.</span><span class="n">deg</span><span class="p">),</span> <span class="n">frame</span><span class="o">=</span><span class="s1">&#39;icrs&#39;</span><span class="p">)</span>

<span class="kn">import</span> <span class="nn">glob</span><span class="o">,</span> <span class="nn">shutil</span>
<span class="k">for</span> <span class="n">vis</span> <span class="ow">in</span> <span class="n">glob</span><span class="o">.</span><span class="n">glob</span><span class="p">(</span><span class="s2">&quot;*/*.ms&quot;</span><span class="p">):</span>
    <span class="n">shutil</span><span class="o">.</span><span class="n">copytree</span><span class="p">(</span><span class="n">vis</span><span class="o">+</span><span class="s2">&quot;/FIELD&quot;</span><span class="p">,</span> <span class="n">vis</span><span class="o">+</span><span class="s2">&quot;/FIELD.backup&quot;</span><span class="p">)</span>
    <span class="n">tb</span><span class="o">.</span><span class="n">open</span><span class="p">(</span><span class="n">vis</span><span class="o">+</span><span class="s2">&quot;/FIELD&quot;</span><span class="p">)</span>
    <span class="n">phasedir</span> <span class="o">=</span> <span class="n">tb</span><span class="o">.</span><span class="n">getcol</span><span class="p">(</span><span class="s1">&#39;PHASE_DIR&#39;</span><span class="p">)</span>
    <span class="n">rownr</span> <span class="o">=</span> <span class="n">np</span><span class="o">.</span><span class="n">argmax</span><span class="p">(</span><span class="n">tb</span><span class="o">.</span><span class="n">getcol</span><span class="p">(</span><span class="s1">&#39;NAME&#39;</span><span class="p">)</span> <span class="o">==</span> <span class="s1">&#39;J1744-3116&#39;</span><span class="p">)</span>
    <span class="k">assert</span> <span class="n">rownr</span> <span class="o">!=</span> <span class="mi">0</span>
    <span class="n">phasedir</span><span class="p">[:,</span> <span class="mi">0</span><span class="p">,</span> <span class="n">rownr</span><span class="p">]</span> <span class="o">=</span> <span class="n">simbad_coord</span><span class="o">.</span><span class="n">fk5</span><span class="o">.</span><span class="n">ra</span><span class="o">.</span><span class="n">wrap_at</span><span class="p">(</span><span class="mi">180</span><span class="o">*</span><span class="n">u</span><span class="o">.</span><span class="n">deg</span><span class="p">)</span><span class="o">.</span><span class="n">rad</span><span class="p">,</span> <span class="n">simbad_coord</span><span class="o">.</span><span class="n">fk5</span><span class="o">.</span><span class="n">dec</span><span class="o">.</span><span class="n">rad</span>
    <span class="n">tb</span><span class="o">.</span><span class="n">open</span><span class="p">(</span><span class="n">vis</span><span class="o">+</span><span class="s2">&quot;/FIELD&quot;</span><span class="p">,</span> <span class="n">nomodify</span><span class="o">=</span><span class="kc">False</span><span class="p">)</span>
    <span class="n">tb</span><span class="o">.</span><span class="n">putcol</span><span class="p">(</span><span class="n">columnname</span><span class="o">=</span><span class="s1">&#39;PHASE_DIR&#39;</span><span class="p">,</span> <span class="n">value</span><span class="o">=</span><span class="n">phasedir</span><span class="p">)</span>
    <span class="n">tb</span><span class="o">.</span><span class="n">flush</span><span class="p">()</span>
    <span class="n">tb</span><span class="o">.</span><span class="n">close</span><span class="p">()</span>
</pre></div>

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