\begin{table}%t4 \caption{\label{surveys}Characteristics of the three surveys discussed in the text, assuming an efficient 1.5~m space telescope with an obscuration of 0.6~m and a total telescope throughput (CCD, mirror, grism) of 70\% using a survey efficiency of 75\%.} \par %\centerline {\small \begin{tabular}{cccc} \hline\hline & DEEP-vis-NIR & DEEP-NIR & WIDE-NIR \\ probe & WL & WL & BAO \\ \hline $T_{\rm obs}$ & 240~ks & 240~ks & 1200~s\\ $\lambda$ in $\mu$m & 0.6--1.7 & 1--1.7 & 1--1.7 \\ 3$\sigma$ at 1.2~$\mu$m & $5\times 10^{-18}$ & $5\times 10^{-18}$ & $1\times 10^{-16}$ \\ & & ergs\ cm$^{-2}$~s$^{-1}$ & \\ area needed & 10~deg$^2$ & 10 deg$^{2}$ & 20~000 deg$^{2}$\\ mission time & 0.2 yrs & 0.2 yrs & 2 yrs\\ & & FOV of 0.5 deg$^{2}$ & \\ nbr density (5$\sigma$)& 60 & 35 & 5\\ & & gal/arcmin$^{2}$ & \\ $z$[1line$3\sigma$] & $0