\begin{table}%t1
\caption{\label{obs-param}Log of the X-ray observations.}
\newcommand{\T}{\rule{0pt}{2.6ex}}
\newcommand{\B}{\rule[-1.2ex]{0pt}{0pt}}
%\centering
\par
\begin{tabular}{c c c c c}
\hline
\hline \noalign{\smallskip}
\textbf{Satellite} \T \B & \textbf{Instrument} & \textbf{Start date} & \textbf{Obs. ID} & \textbf{Exposure time (ks)} \\
\hline
\chandra \T & ACIS-S & 2000 April 20 & 398 & 1.4 \\
\xmm\tablefootmark{a} \T & EPIC & 2004 May 23 & 205010101 & 34/35.5/35.5 \\
\chandra \T & ACIS-S & 2005 February 02 & 4741 & 37 \\
\chandra \T & ACIS-S & 2006 March 16 & 7077 & 110 \\
\chandra \T & ACIS-S & 2006 July 25 & 7078 & 51 \\
\chandra \T & ACIS-S & 2006 October 24 & 7079 & 105 \\
\chandra \T & ACIS-S & 2007 February 20 & 7081 & 110 \\
\chandra \T & ACIS-S & 2007 April 20 & 7080 & 55 \\
\hline
\end{tabular}
\tablefoot {\tablefoottext{a}{Exposure time for pn/MOS1/MOS2 respectively.}}
\vspace*{5mm}
\end{table}