At some redshift beyond 10 in a CDM Universe objects will start to form which are sufficiently massive to lead to the production of primordial star clusters. The process of reionisation also probes the range, allowing discrimination between competing CDM cosmological models which predict fluctuations on such scales. However the telescope specifications for making such observations are highly dependent on the redshift of interest, and are shown in Table 1 . In some senses, an instrument designed solely to investigate the very high redshift universe would have specifications easier to meet than one designed to investigate more recent redshifts. There are many anticipated problems deriving from various sources of interference, and this subject has been addressed to a greater or lesser extent elsewhere with various proposed strategies for minimisation of the effects.
Confusion is also a major problem.
So this area will need a lot of effort if a low resolution array requires this to be bettered by more than two orders of magnitude. Aspects of the confusion problem also imply limitations for the field of view. A wider field of view implies worse confusion. Assuming 4 hours per field, to map the whole sky in ten years only needs a field of view of 1 degree. This in turn implies a maximum element size of 130m.