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First light for SKA prototype antennas
from Contact 15
BY THE SKAO AND MAX PLANCK INSTITUTE FOR RADIO ASTRONOMY
As construction on the SKA telescopes continues apace, prototype instruments have been reaching their own milestones: achieving “first light”. Technology demonstrators in Australia and South Africa are being used to test systems and help the SKAO to prepare for commissioning of the full-scale telescopes in the coming years.
In January, the first prototype dish of the SKA-Mid telescope constructed on site in South Africa created its first image. The prototype, assembled in mid-2018, is a fully functioning single-dish radio telescope in its own right, funded by Germany’s Max Planck Society for technical commissioning and scientific use. Known as SKAMPI, it was designed by the SKAO’s international Dish consortium, involving institutions in 10 countries and led by CETC54 in China, where it was also manufactured.
SKAMPI’s first light image of the Southern Sky at 2.5 GHz wavelength demonstrates that the technology is working as expected, and although the uncalibrated measurements are still affected by radio frequency interference (RFI), atmospheric and system variations, the image already reveals much of the characteristic radio emission of our Milky Way and external galaxies such as Centaurus A. The team also tested out the dish’s pulsar mode, detecting the Vela pulsar.
“Tests of the SKAMPI prototype have already provided invaluable measurements of key performance parameters. These have been used to refine the design of the SKAMid dishes to ensure that they meet our demanding requirements for pointing and surface accuracy,” said SKAO Head of System Science Dr Robert Laing. “The test procedures developed for SKAMPI will also be used to qualify the new SKA-Mid dishes before they are integrated into the array.”
SKAMPI will enter full science operations later this year, with further technical developments planned. Although much of its observing time will be dedicated to science programmes defined by the SKAMPI team, requests for observations will also be open to the South African and German science communities, and setting up an educational programme for schools and universities is under consideration.
A couple of months earlier on the other side of the Indian ocean, the SKA-Low technology demonstrator Aperture Array Verification System 3 (AAVS3) also achieved first light.
Comprising one full station of 256 SKA-Low antennas, it is designed to verify that performance, cost, and schedule are maintained on SKA-Low’s eventual 131,072 antennas. The demonstrator is located at Inyarrimanha Ilgari Bundara, the CSIRO Murchison Radio-astronomy Observatory, where SKA-Low is now under construction.
AAVS3 uses the fourth generation of SKA-Low antenna design, optimised by the Italian National Institute for Astrophysics (INAF) in collaboration with CNR-IEIIT and the Italian industrial partner SIRIO Antenne, building on previous designs developed within an international consortium involving six countries.
It uses a different layout to previous demonstrator stations, and has helped to determine the optimal configuration to minimise interference between the antennas.
One week after a test readiness review, the Assembly Integration and Verification (AIV) and Operations team captured 45 minutes of data with AAVS3 during the Sun’s transit.
Associate Prof. Randall Wayth from Curtin University calibrated and imaged the data. The arcing pale band of the Milky Way’s galactic plane is clearly visible, with the brighter spots of the Centaurus A galaxy and our Sun on the right of the picture.
“It is incredible to see how 256 antennas with less than 40 m of baseline have managed to capture so many details of the full sky. I found this pretty remarkable, and it is extremely encouraging for the performance of the full array,” said SKA-Low Station Integration Engineer Marco Caiazzo.
“The significance of this image is the validation that the station is working as expected. This will help to accelerate the verification program in preparation for AA0.5, the first stage of SKA-Low telescope delivery.”
