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 <h2>AIA data at Visual Wavelengths  </h2>
 
  <p class="defn"><i>
One of the filters on telescope 3 is optimized to observe a ~500 &#8491 FWHM band pass centered at 4500 &#8491. These level 1, 4069 x 4096 data images have undergone processing which includes bad-pixel removal, despiking and flat-fielding and can be found in the JSOC series <a href="http://jsoc.stanford.edu/ajax/exportdata.html?ds=aia.lev1_vis_1hs">aia.lev1_vis_1h.  </a>  .    </i>

</p>

<h4> Keywords:</h4>
<p class="reg"> 

The Primary Keywords for the aia.lev1_euv data are T_REC (the time of the observations) and WAVELNGTH (Wavelength of observation in Angstroms). The WAVELNTH keyword (an integer) must be 4500. FITS header keywords for the AIA data are explained 
<a href="/auto/home1/jsoc/keywords/JSOC_Keywords_for_metadata.pdf">here</a>. 
WCS coordinate keyword descriptions can be found in <a href="relevant_papers/ThompsonWT_coordSys.pdf">this paper</a>.
</p>

<h4> Algorithm For Calculation:</h4>

<p class="reg">
The raw telemetry data obtained from the AIA instrument is considered to be the Level 0 data. Processing Level 0 data to Level 1 involves the following steps: <ul>
<li> Removal of "over scan" rows and columns. </li>
<li> Removal of a dark image to account for the digital offset of the camera, CCD read noise and dark current.    </li>

<li>  Flat-field correction to account for detector non-uniformities, gain differences between CCD quadrants, vignetting and shadowing caused by focal plane filter nickel mesh. </li>

<li> Correction to individual pixels using two algorithms is done. First to permanently correct "bad" pixels that do not respond correctly to light and second, to remove the "spikes" that appear as a result of the interaction of energetic particles that either deposit energy directly in the CCD, or interact with the instrument structure and give rise to high-energy photons that are detected in the CCD.  </li>

<li> The AIA images are flipped so as to put the solar North at the top of the array. he corresponding metadata are updated and additional information about the image and spacecraft housekeeping data (roll angle) is added.
  </li>
<li>Note that these data are not exposure time corrected.  </li>
</ul>
</p> what about Level 1.5 data? 
</p>
<h4> Processing:</h4>
 
<p class="reg">The link to the AIA pipeline processing is ??<br/>

The status of the JSOC pipeline processing can be checked<a href="http://jsoc.stanford.edu/data/jsoc_proc_status.html"> here.</a><p>

<h4> Calibration:</h4>
AIA calibration is described in detail in <a href="http://jsoc.stanford.edu/Priya/JSOC/docs/AIA_calibration.pdf"> Boerner et al(2011)</a>. The calibration data are based on algorithms that are time dependant and include the camera gain, effective area, pointing information, bad-pixel list ,flat field, and average band pass effective area. As newer calibration data becomes available, Level 1 data can be reprocessed using the most recent calibration data. 

<h4> Status Notes and/or Known Problems: </h4>
 
 
 
 
 
 
 
 
 
 
 
 
 
 
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