Load calibration and determination of the zenith opacity

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Load calibration and determination of the zenith opacity

The hot and cold load as well as the atmosphere in a region devoid of signal are measured in turn. From Eq. 2, it is easy to show that

(11)
where

- and are the Rayleigh-Jeans temperature of the loads;
- and are the associated measured counts.

From this equation, we deduce . Using an atmospheric model and Eqs. 7–9, the total opacity of the atmosphere at signal and image frequencies are then fitted.