This plot shows which of both detectors is in use.
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<ul>
<li>Red points for the red-sensitive <b>MIT</b> detector, used as the default one</li>
<li>Blue points for ther blue-sensitive <b>EEV</b> detector, mostly used for visitors</li>
</ul>

Each detector is a mosaic composed of two chips, the upper and the lower chip. 

The data are retrieved from pipeline processed bias frames for both
chips of the mosaic detector separately to monitor potential failures
of one of the two chips.