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Partial Beam Coverage

This scheme has been implemented on Plateau de Bure, where the dynamic range of the detectors is relatively small (only 2 between optimum sensitivity and saturation). The only change from the standard equations presented before is the introduction of the ``beam filling factor'' or ``calibration efficiency'' $C_{eff}$ in the output on the chopper (from Eq. (1-2))
\begin{displaymath}
Mean\_load / K = Trec + C_{eff} * T_{load} + (1-C_{eff}) * T_{emi}
\end{displaymath} (17)

Algebra similar to that already exposed yields

\begin{displaymath}
Tcal = C_{eff} * \frac{(T_{load} - T_{emi}) * (1. + Gain\_i)}
{B_s * e^{-Tau\_s * Air\_mass}}
\end{displaymath} (18)

just correcting $Tcal$ by an additional $C_{eff}$ scaling factor.

In TREC mode, the sky emission is derived by

\begin{displaymath}
T_{emi} = \frac{(T_{load} + Trec) * Mean\_atm * C_{eff}}
{Mean\_load - (1-C_{eff})*Mean\_atm} - Trec
\end{displaymath} (19)

and in AUTO mode, the receiver temperature may be derived by
\begin{displaymath}
Trec = \frac{C_{eff} * Mean\_atm * T_{load} - (Mean\_load - (1-C_{eff})
* Mean\_atm) * T\_emi}{Mean\_load - Mean\_atm}
\end{displaymath} (20)



Gildas manager 2018-12-15