According to a media release by the South African Radio Astronomy Observatory (SARAO), the Square Kilometre Array- Max-Planck-Institut für Radioastronomie (SKA-MPIfR) Telescope in South Africa is ready for science operations. The journey into the golden age of radio astronomy continues with the SKA telescopes, which will become Earth’s largest radio telescope arrays in the coming years. The MPIfR in Bonn has played an active role in their development over the past decades. Germany will become a full member of the international SKA Observatory – the intergovernmental organisation currently building the telescopes in Australia and South Africa – in early 2024.
Furthermore, to develop key technologies with unique scientific benefits, the MPIfR, together with Otto Hydraulik Bremen (OHB) Digital Connect GmbH and the South African Radio Astronomy Observatory, have built the SKA-MPIfR telescope (SKAMPI), a prototype dish for the SKA-Mid telescope, for technical commissioning and scientific use.
The SKA-MPIfR telescope (SKAMPI) was fully assembled in mid-2018 at the South African SKA site in the Karoo semi-desert. Initial test observations took place in December 2019. Technical commissionings such as system evaluation, radio-frequency interference testing, and performance testing took place until early 2022, leading to the SKA system design qualification documents being published in 2022. Since then, developments have been pursued, setting up a framework to operate SKAMPI remotely and as a robotic system, integrating telescope operations with frontend and backend control, and synchronising observations with data acquisition and automated calibration.
“With a fully digital frontend, SKAMPI has two receiver units, for the S-band between 1.75 GHz and 3.5 GHz and the Ku-band between 12.0 GHz and 18.0 GHz,” says Gundolf Wieching, the Head of the Electronics Technical Division at MPIfR. “The receivers are based on the MPIFR S-band system designed for MeerKAT, and the data acquisition and processing system or “backend” is a high-performance computer system developed by the MPIfR, using predominantly graphic-processing-units (GPUs) as accelerators cards for computing in standard commercial servers.” The backend system can be dynamically adapted to serve different science cases like pulsars, spectropolarimetry observations or VLBI. The size of SKAMPI, with a projected aperture of 15 m in combination with a site protected against radio frequency interference, offers a rare combination of a large field of view and, thus, fast sky coverage, with excellent polarisation properties to investigate magnetic fields in the universe.
“We have performed first-light observations with SKAMPI in the S-band at frequencies between 1.75 and 3.5 GHz, demonstrating the telescope’s spectral and pulsar capabilities with imaging of the radio emission of the Southern Sky and detection of the Vela pulsar,” says Hans-Rainer Klöckner from MPIfR, the SKAMPI project scientist.
The radio emission of the Southern Sky in Galactic coordinates demonstrates the spectral mode and imaging capabilities of SKAMPI. The entire sky was observed on two consecutive nights at a slewing speed of 2.5 degrees per second. Although the uncalibrated measurements are still affected by radio frequency interference 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 and promises to achieve the goal of producing one of the most sensitive sky surveys. “This image is an important step in the imaging commissioning process, demonstrating the suitability of the telescope and our approach for large-scale imaging,” says Ferdinand Jünemann from MPIfR, who is using the data for his PhD research. “Currently, we have 40 times more observations to process for the first total power release of a complete Southern Sky Survey in the S-band.”
SKAMPI’s ability to observe radio pulsars – rapidly rotating neutron stars that shine bright beams for radio light from above their magnetic poles as they spin – has been demonstrated with first-light observations of the well-known Vela pulsar. The detection of the Vela pulsar closely matches expectations from the literature and bodes well for future long-term studies of bright pulsars with SKAMPI.
The first light measurements provide a first glimpse of the data quality and capabilities of the telescope, ensuring a unique scientific exploration. Full science operation will begin this year, and dedicated programmes will include studying the nature of variable sources such as active galactic nuclei or fast radio bursts, monitoring strong pulsars for rotational or magnetospheric events, investigating the inner workings of bursts detected with the FERMI satellite as part of a small VLBI telescope array, and improving our understanding of the Galactic foreground.
In parallel with the initial science programmes, further technical developments are planned, including advanced calibration strategies and establishing a framework to transform SKAMPI into a fully robotic system. Such a framework will combine operational, mechatronic and data processing information and allow evaluation of the entire signal processing path to the final scientific data product.
“For SKAMPI, we have extended our software system so that computing resources not needed for the real-time signal processing of the current observation can be used by scientists for first automated analyses,” explains Tobias Winchen, also from MPIfR. “The results are available shortly after the observations and provide fast feedback on the observations and system performance. Soon, we will start testing a fully automated system that includes the output of the automated analyses to manage all the observations of a scientific programme.”
Although much of the observing time on SKAMPI will be dedicated to science programmes, requests for observations will be open to the South African and German communities, and there will also be an opportunity to set up an educational programme for schools and universities.
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