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.