SKA Memo 46
18 Feb 2004

SKA Imaging

Melvyn Wright, 
Radio Astronomy laboratory, 
University of California, Berkeley, CA, 94720

In this memo, we explore the imaging requirements and data processing
options for the large N SKA.  We discuss imaging from the sampled cross
correlation function and direct imaging by beam formation. Cross
correlation of all antennas provides the most complete sampling of the
incident wavefront and allows imaging the full field of view of the
individual antennas.  Extrapolation of existing and planned  radio
astronomy correlators suggests that a 4000 antenna, 1 GHz bandwidth
correlator is feasible by 2020.  Direct image formation requires 
GHz data processing to phase the signals from all the antennas over
a 10^6 pixel image.  The calibration must be made in close to real
time with the derived calibration parameters fed back into the real
time system for multiple phase centers.  The large data rate and data
processing requirements suggests that the SKA should produce final,
calibrated images as its normal output.