\begin{table}%t1
%\centering
 \caption{Double and single asteroid mission opportunity
with fly-by between 2008 and 2010. The listed $\Delta V$ values were
estimated before the launch.} \label{tab1}
\par
\begin{tabular}{lr|lr} \hline \hline
Double fly-by &  $\Delta V$ m/s &  Single fly-by 
& $\Delta V$ m/s
\\ \hline
Rhodia $+$ Lutetia & 159 & Lutetia & 125 \\
Steins $+$ Lutetia  & 139  & Rhodia & 97 \\
Luichewoo $+$ Lutetia & 129 & Steins &57 \\
Baetsle $+$ Izvekov & 73 & Sofala & 101 \\
Baetsle $+$ Fogelin & 79 & Fogelin & 18\\
Luichewoo $+$ Izvekov & 32 & Baetsle & 19 \\
Rhodia $+$ Izvekov & 112 & Luichewoo & 32\\
Rhodia $+$ Fogelin & 113 & Carrera & 102\\
Steins $+$ Izvekov  &77 & Izvekov & 15 \\
Sofala $+$ Izvekov & 146 & &\\
Steins $+$ Fogelin  & 83 & &\\
Luichewoo $+$ Fogelin &35 & &\\
\hline
\end{tabular}
\end{table}