\begin{table}%t7
\caption{\label{TabCoupLev}Optical coupling of payload elements to detectors}  
%\centering
\par
\begin{tabular}{lcccccc}
\hline \hline \noalign{\smallskip}
   & Emissivity\tablefootmark{a}
   & Temp. fluctuation\tablefootmark{b} &
    \multicolumn{4}{c}{Frequency (GHz)\tablefootmark{c}} \\
   &  &  & 30 & 70 & 100 & 353 \\
  \hline \noalign{\smallskip}
  Baffle & 0.05 & 30 & $1.7 \times 10^{-3}$ & $2.3\times 10^{-3}$ & $1.7\times 10^{-3}$ & $2.5\times 10^{-4}$ \\
  Groove 3 (inside baffle) & 0.05 & 9.5 & $2.3\times 10^{-4}$ & $2.7\times 10^{-4}$ & $4.0\times 10^{-4}$ & $3.7\times 10^{-5}$ \\
  Groove 3 (outside baffle) & 0.05 & 6.5 & $2.3\times 10^{-7}$ & $1.7\times 10^{-7}$ & $1.7\times 10^{-7}$ & $7.7\times 10^{-8}$ \\
  PR (central sector) & 0.02 & 0.2 & 0.74 & 0.74 & 0.74 & 0.74 \\
  PR (Moon-illuminated upper sector) & 0.02 & 1.3 & $6.1\times 10^{-4}$ & $6.1\times 10^{-4}$ & $6.1\times 10^{-4}$ & $6.1\times 10^{-4}$ \\
  PR (outer sector) & 0.02 & 1.1 & 0.26 & 0.26 & 0.26 & 0.26 \\
  SR  & 0.02 & $<$0.01 & 1.0 & 1.0 & 1.0 & 1.0 \\
  \hline
\end{tabular}
\tablefoot {\tablefoottext{a}{Conservatively high value. More realistic values are given in Sect.~4.} \\
\tablefoottext{b}{Maximum fluctuation amplitude at 1/60~Hz ($\mu$K). The dominant fluctuation source is the Moon illumination for all surfaces but the 3${\rm rd}$ V-groove and the SR (which are dominated by the sorption cooler). Moon illumination will be avoided by mission planning, in which case the lower SR levels are applicable also to the PR and the baffle.} \\
\tablefoottext{c}{A specific detector has been arbitrarily chosen for the calculation of the  coupling, which is representative of all detectors.}}
\vspace*{5mm}
\end{table}