\begin{table}%t1
%\centering
\par
\caption{\label{tab:table1}Observation log of the data of \object{TW Hya}. }
\begin{tabular}{l@{\ }l@{\ }l@{\ }l@{\ }c@{\ }}
\hline
\hline
Obs~ID~~&Instrument ~~       &Grating~~  &  Start Date~~&Exp.(ks)\\
\hline
6443~~  &HRC-S      ~~       &LETG~~    &  2006-08-22T07:47:56~~ &151.64~ \\
\hline
\end{tabular}
\end{table}