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Foreground removal is a major challenge for detecting the redshifted 21 cm neutral hydrogen (H i) signal from the Epoch of Reionization. We have used 150 MHz Giant Metrewave Radio Telescope observations to characterize the statistical properties of the foregrounds in four different fields of view. The measured multifrequency angular power spectrum C_ℓ(Δν) is found to have values in the range 10⁴–2 × 10⁴ mK² across 700 ≤ ℓ ≤ 2 × 10⁴ and Δν ≤ 2.5 MHz, which is consistent with model predictions where point sources are the most dominant foreground component. The measured C_ℓ(Δν) does not show a smooth Δν dependence, which poses a severe difficulty for foreground removal using polynomial fitting.

The observational data were used to assess point source subtraction. Considering the brightest source (∼1 Jy) in each field, we find that the residual artefacts are less than 1.5 per cent in …