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.
Giulia Macario, Giuseppe Pupillo, Gianni Bernardi, Pietro Bolli, Paola Di Ninni, Giovanni Comoretto, Andrea Mattana, Jader Monari, Federico Perini, Marco Schiaffino, Marcin Sokolowski, Randall Wayth, Jess Broderick, Mark Waterson, Maria Grazia Labate, Riccardo Chiello, Alessio Magro, Tom Booler, Andrew McPhail, Dave Minchin, Raunaq Bhushan
The low frequency component of the Square Kilometre Array (SKA1-Low) will be an aperture phased array located at the Murchison Radio-astronomy Observatory (MRO) site in Western Australia. It will be composed of 512 stations, each consisting of 256 log-periodic dual-polarized antennas, and will operate in the low frequency range (50 to 350 MHz) of the SKA bandwidth. The Aperture Array Verification System 2 (AAVS2), operational since late 2019, is the last full-size engineering prototype station deployed at the MRO site before the start of the SKA1-Low construction phase. The aim of this paper is to characterize the station performance through commissioning observations at six different frequencies (55, 70, 110, 160, 230, and 320 MHz) collected during its first year of activities. We describe the calibration procedure, present the resulting all-sky images and their analysis, and discuss the station calibratability and system stability. Using the difference imaging method, we also derive estimates of the SKA1-Low sensitivity for the same frequencies and compare them with those obtained through electromagnetic simulations across the entire telescope bandwidth, finding good agreement (within 13%). Moreover, our estimates exceed the SKA1-Low requirements at all considered frequencies by up to a factor of ∼2.3. Our results are very promising and allow for an initial validation of the AAVS2 prototype station performance, which is an important step toward the coming SKA1-Low telescope construction and science.
We present the Engineering Development Array 2, which is one of two instruments built as a second generation prototype station for the future Square Kilometre Low-Frequency Array. The array is comprised of 256 dual-polarization dipole antennas that can work as a phased array or as a standalone interferometer. We describe the design of the array and the details of design changes from previous generation instruments, as well as the motivation for the changes. Using the array as an imaging interferometer, we measure the sensitivity of the array at five frequencies ranging from 70 to 320 MHz.
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