Observations of the HI 21cm transition line promises to be an important probeinto the cosmic dark ages and epoch of reionization. One of the challenges forthe detection of this signal is the accuracy of the foreground source removal.This paper investigates the extragalactic point source contamination and howaccurately the bright sources ($\gtrsim 1$ ~Jy) should be removed in order toreach the desired RMS noise and be able to detect the 21cm transition line.Here, we consider position and flux errors in the global sky-model for thesebright sources as well as the frequency independent residual calibrationerrors. The synthesized beam is the only frequency dependent term includedhere. This work determines the level of accuracy for the calibration and sourceremoval schemes and puts forward constraints for the design of the cosmicreionization data reduction scheme for the upcoming low frequency arrays likeMWA,PAPER, etc. We show that in order to detect the reionization signal thebright sources need to be removed from the data-sets with a positional accuracyof $\sim 0.1$ arc-second. Our results also demonstrate that the efficientforeground source removal strategies can only tolerate a frequency independentantenna based mean residual calibration error of $\lesssim 0.2 %$ in amplitudeor $\lesssim 0.2$ degree in phase, if they are constant over each days ofobservations (6 hours). In future papers we will extend this analysis to thepower spectral domain and also include the frequency dependent calibrationerrors and direction dependent errors (ionosphere, primary beam, etc).
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