EVLA Memo 64 Wide-Field Imaging with the EVLA: WIDAR Correlator Modes and Output Data Rates

Of all the anticipated imaging problems to be undertaken by the EVLA, the most demanding, both in terms of data rate, data storage and post-processing, will likely be that of wide-band, wide-field imaging imaging the entire antenna primary beam with the full bandwidth. In this memo, I summarize the correlator requirements for various observing scenarios with the EVLA: distortion-free imaging of the entire primary beam with, and without high levels of RFI; and targeted imaging within the primary beam, with and without high levels of RFI. The capabilities of the WIDAR correlator are described, and the modes which best match the observing requirements are identified. In general, the correlator is an excellent fit for wide-band, widefield imaging in the VLA's standard configurations. However, for the full EVLA which incorporates the New Mexico Array, the WIDAR correlator will not in general be capable of simultaneously providing full band coverage and full beam imaging without accepting significant image degradation. The shortfall is particularly noted at the lower frequencies.