'On-the-fly' mapping

The MeerKAT correlator does not innately support on-the-fly mapping, i.e. continous adjustments of the delay tracking centre while the antennas slew. However, it has been shown to be possible to correlate scanning observations after the fact to enable interferometric imaging. We briefly summarise the efforts in this direction below.

The HI intensity mapping project conducts scans at a fixed elevation angle while scanning at 5 arcmin/s, with a 2s integration time. The correlator delay tracking centre is set to the central azimuth, elevation point of the the scan, which effectively tracks the changing right ascension at that point.

Primary beam smearing is shown to be neglible (amplitude error <5%) at slow scanning speeds over a 2s integration.

Open

The typical scanning pattern (one hour segment) for asynchronous OTF mapping.

Bandpass and gain calibrators are tracked for the standard duration and cadence.

This report describes the prototype data pipeline used to apply a phase rotation to each integration. The resulting test image shows excellent image quality with no visible trace of imaging artefacts and rms noise close to the expected level of ~0.33 mJy/bm (see Figure 4 of attached report). For further information contact Mario Santos.