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Warm-starting Apertif: Improved Images

Submitter: Betsey Adams
Description: During the science verification campaign, a new mode for starting the Apertif system was developed. Termed "warm start", this mode keeps the system, namely the beamweights, in a better state by avoiding power-cycling of digital components which cause phase errors. This resulted in huge improvements for the science performance of the system. For the imaging team, this meant both lower noise and fewer calibration errors.

The images above show 12-hour target field observations from before the warm start was implemented (left) and after (right). Although they are of different fields, the two images feature the same grey colourscale so you can clearly see the lower noise and more sources detected after the warm start. In addition, fewer sources have artifacts (rings) around them after the warm start, and these tend to be brighter and complicated sources, where this is expected. Before the warm start mode, many sources had artifacts around them, which limited our ability to measure source properties.
Copyright: ASTRON, Apercal
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