The Aperture Array Verification System, or AAVS, is a series of incremental proof-of-concept Square Kilometre Array (SKA) low-frequency stations. They have been deployed at Inyarrimanha Ilgari Bundara, the CSIRO Murchison Radio-astronomy Observatory, recognizing and acknowledging the Wajarri Yamaji as the Traditional Owners. With three iterations, AAVS has been a means to end-to-end test the proposed antennas and station layout of the SKA-Low telescope. The third iteration is the first to be deployed and operated by the SKA Observatory directly and was implemented as a way to investigate the performance of different antenna layouts within a station (randomized, Vogel and perturbed Vogel). SKAO Science Operations has embraced this opportunity to enable early engagement with the prototype to test and explore aspects of telescope operations, including scheduling and observing, as well as monitoring and processing the subsequent data (together with the System Science and Commissioning teams). In this paper we provide a description of the AAVS3 system, developments on site in Australia, the observations undertaken with AAVS3, and the learning and development for scientific operations that has been enabled by the AAVS system. There is also a forward look more broadly to science operations and verification, including the timeline and upcoming array assembly schedule.
Stations of dipole antennas for SKA1-Low will comprise 256 elements spread over an area with a diameter of 38 m. We consider the effect of residual unsubtracted sources well outside of the main beam for differing numbers of unique station configurations, in the epoch of reionization (EoR) and the cosmic dawn (CD), both in simulation and with theoretical considerations. We find that beam sidelobes imprint power that renders the cosmological signal unobservable over a range of scales unless compact sources are subtracted beyond θZ = 30 degrees from zenith, and that station apodization will likely be required to control far sidelobes. An array with Nb = 4 unique station configurations is sufficient to reduce the contamination, with an increase to Nb = 8 showing little improvement. Comparison with an achromatic Airy disk beam model shows that beam sidelobe level is the main contributor to excess power in the EoR window, and beam chromaticity is less relevant. In the EoR, z = 8.5, subtracting sources above 200 mJy out to θZ = 45 deg, will be required to access relevant modes of the power spectrum.
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