SKA-Low prototype station performance are initially validated

With the recent start of the construction phase of the SKA Observatory radio telescope, its low-frequency (50-350 MHz) component, named SKA-Low, is going to be built at the Murchison Radio-astronomy Observatory (MRO) site in Western Australia. Once completed, SKA-Low will be an aperture phased array with no moving parts, composed by 512 stations, half located within a very dense core (about 1 km diameter), half distributed along three quasi-spiral arms (up to a maximum baseline of 65 km). Each station will be composed of 256 SKALA4.1 log-periodic dual-polarization fixed antennas made in Italy, pseudo-randomly distributed across a circular area of about 40 m diameter, with highly flexible digital beam-forming driven by advanced electronics.

Within the INAF Low Frequency Aperture Array (SKA-LFAA) team, a growing number of researchers in the radio astronomy group at INAF-Osservatorio Astrofisico di Arcetri has been highly involved in the electromagnetic design and numerical validation of the SKA-Low station, as well as in the design and testing of the station beamforming hardware. 

In particular, the INAF-OAA group has actively contributed to the preliminary observational characterization of the performance of AAVS2 (Aperture Array Verification System 2), the last full-size engineering prototype station of SKA-Low deployed on site (see Figure A). The group has developed procedures to process, image and analyse a large amount of interferometric data obtained from commissioning AAVS2 observations. Thanks to this effort, SKA-Low crucial performance such as sensitivity, imaging quality, calibratability and system stability have been initially validated at six different frequencies (55, 70, 110,160, 230, and 320 MHz) sampling the SKA-Low bandwidth. Work is ongoing to characterise the station polarisation performance (see publication link below, and Figures B and C).

An assembly of six stations like AAVS2, to be built in the next three years, will form the first production prototype of the SKA-Low telescope. The results from these activities thus represent an important step towards the coming SKA-Low construction and science.

  1. Credits SKAO - Aerial view of the upcoming SKA-Low array: some stations are represented on top of a real picture of the site. The left side of the front station is the real AAVS2 prototype, with SKALA4.1 antennas
  2.  Comparison between AAVS2 observed (top) and simulated (bottom) all sky images  at 70 MHz (Macario et al 2022)
  3. SKA1-Low sensitivity across the bandwidth derived from AAVS2 observations (black squares) and simulations (blue and green symbols). The red crosses are SKA1-Low the requirements. (Macario et al 2022)


Reference: Macario et al., Characterization of the SKA1-Low prototype station Aperture Array Verification System 2J. of Astronomical Telescopes, Instruments, and Systems, 8(1), 011014, (2022). 

Team INAF-OAA involved in these activities: Pietro Bolli, Paola Di Ninni, Georgios Kyriakou (EM analysis), Giovanni Comoretto, Simone Chiarucci, Carolina Belli, Carlo Baffa (station beamforming), Giulia Macario (astronomical observations). See the webpage.