Keywords: pdbi-amp-cal

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## CAL COLD calibration

This is the most complete calibration procedure, with the minimum number of assumptions. The first step is to measure the power detected by the receiver on the Sky, then on a warm load (the Chopper), then on a cold (liquid nitrogen) load, averaged over the channels of a specific backend. For a perfectly linear detector, the output power is proportional to the total input noise (Receiver + Load), hence the receiver temperature is simply given by

| (12)

Then, one can proceed as in TREC mode.

The description above refers to what happens when OBS when you use the CAL COLD command (in either TREC or AUTO mode).