\begin{table}%t2
\caption{Mean observation parameters:
MPIfR comet observation campaign 2001--2004. 
\label{obs_param_table}}
%\centerline
 {\begin{tabular}{lccrrccccccc}
\hline \hline 
% & &  \\[-3mm]
Comet  & \multicolumn{1}{c}{$\Delta t~$ $^a$}
& \multicolumn{1}{c}{Elevation} 
& \multicolumn{2}{c}{RA\_(J2000)\_Dec}
& \multicolumn{1}{c}{$\Delta$} & \multicolumn{1}{c}{$r$}
& \multicolumn{1}{c}{$\angle$SEC $^b$}
& \multicolumn{1}{c}{$\angle$SCE $^c$}
& $d$ $^d$ 
& $\Delta \theta$ $^e$ 
& \underline{~~$d$ }  \\
~~date  & \multicolumn{1}{c}{(min)} 
&  \multicolumn{1}{c}{($\circ$)} & (h mn) & ($\circ$ $\prime$) &
\multicolumn{1}{c}{(AU)} & \multicolumn{1}{c}{(AU)}
& \multicolumn{1}{c}{($\circ$)} & \multicolumn{1}{c}{($\circ$)}
& (10$^3$ km) & (10$^3$ km) & $\Delta \theta$ $^e$ \\[1mm]
\hline 
% & &  \\[-3mm]
\multicolumn{7}{l}{\underline{C/2001 A2-B (LINEAR)} in 2001}\\
~~07.22 Jul. & 70 & 43 & 23 31 & 05 37 & 0.262 & 1.130 & 109 & 58 & 9.7 & 7.9 & 1.22 \\
\multicolumn{7}{l}{\underline{153P/Ikeya-Zhang} in 2002}\\
~~25.42 Apr. & 53 & 57 & 20 50 & 61 29 & 0.409 & 0.974 & 74 & 83 & 9.5 & 12.3 &
0.77 \\
~~04.40 May & 83 & 58 & 18 19 & 55 30 & 0.410 & 1.124 & 95 & 63 & 11.8 & 12.3 &
0.96 \\
~~06.38 May & 17 & 51 & 17 55 & 52 38 & 0.416 & 1.157 & 100 & 59 & 12.3 & 12.5 &
0.98 \\
~~07.41 May & 45 & 54 & 17 43 & 51 14 & 0.421 & 1.174 & 102 & 57 & 12.6 & 12.7 &
0.99\\
\multicolumn{3}{l}{\underline{C/2001 Q4 (NEAT)} in 2004}\\
~~08.73 May & 47 & 29 & 07 44 & --07 53 & 0.327 & 0.970 & 74 & 87 & 9.3 & 9.9 & 0.94 \\
~~13.69 May  & 90 & 53 & 08 23 & +13 54 & 0.390 & 0.963 & 72 & 86 & 9.1 & 11.7 & 0.78 \\
~~17.65 May  & 82 & 65 & 08 47 & +25 42 & 0.473 & 0.962 & 70 & 82 & 9.1 & 14.3 & 0.64 \\
\multicolumn{3}{l}{\underline{C/2002 T7 (LINEAR)} in 2004}\\
~~08.40 May & 35 & 35 & 00 41 & $-$4 06 & 0.534 & 0.699 & 41 & 109 & 5.4 & 16.1 & 0.34 \\
~~13.44 May & 63 & 28 & 01 43 & $-$10 06 & 0.364 & 0.755 & 38 & 125 & 6.0 & 11.0 & 0.55 \\
\hline 
\end{tabular}}
\par
\smallskip
$^a$ {Integration time on comet.}\\
$^b$ {Sun-Earth-Comet, solar elongation angle.}\\
$^c$ {Sun-Comet-Earth, phase angle.}\\
$^d$ {Estimated NH$_3$ coma diameter.}\\
$^e$ {MPIfR beam diameter (3 dB) at comet.}
\end{table}