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Access to Nyquist-sampled voltages from tied-array beams:

Access to Nyquist-sampled voltages from tied-array beams: Four or more tied-array beams required, at any point in the full field of view; Tied-array inputs should be delayed to a common point and fringe-rotated;

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Access to Nyquist-sampled voltages from tied-array beams:

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  1. Access to Nyquist-sampled voltages from tied-array beams: • Four or more tied-array beams required, at any point in the full field of view; • Tied-array inputs should be delayed to a common point and fringe-rotated; • Full flexibility as to which antennas are used in the individual tied-array beams; • Ability to re-phase tied-array regularly. • Circular polarisations required (minimum leakage). • Channelised voltages acceptable at 1, 2, 4, 8, 16, 32, 64, 128 and 256 MHz bandwidths: • Dual polarisation; • Up to 16 channels selectable for recording (contiguous or non-contiguous); • Tunable over the instantaneous bandwidth; • 2, 4, or 8 bit samples. Real voltages? • Continuous data streams, made available to recording system on 10 Gbps ethernet: • VLBI Data Interchange Format (VDIF) used for framing the data. • Tsys calibration (every ~10 sconds), phase stable system (phase returns after frequency/source changes), on-source logging: • Hydrogen maser preferred for time keeping. • Maximum data rate of 32, 768 Mbps. Transferred to recording system in Geraldton via fibre. • Hardware in Geraldton ~5 kW initially and ~20 kW in long term; • Possible hardware on site initially if single pixel feed is adopted; • Final processing of data at LBA correlation facility at Curtin (ship disks initially and network • transfer in long term). • Limited commensal observing possibilities (fast transients and deep continuum survey). VLBI requirements for ASKAP ASKAP f2f April 15, 2009Prof. Steven Tingay (on behalf of the ASKAP VLBI team)

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