\begin{table}%t1
 %\centering
\par
\caption{\label{tab:planck}Instrumental characteristics of \textit{Planck}-HFI$^{{\rm a}}$.}
       \begin{tabular}{ccc}
        \hline\hline        \noalign{\smallskip}
        channel (GHz) & $\theta_{{\rm fwhm}}$ (arcmin) & $\sigma_{{\rm T}}$ ($\mu$K.sr$^{~ -0.5}$) \\
                \hline
                 100 &  9.5 & 6.8    \\
         143 &  7.1 & 6.0    \\
         217 &  5.  & 13.1   \\
         353 &  5.  & 40.1   \\
         545 &  5.  & 401    \\
         857 &  5.  & 18~300. \\ 
                \hline
    \end{tabular}
\tablefoot{\tablefoottext{a}{\citep[See][]{Bluebook2005}.}}
\end{table}