SKAMPI Takes Off

The SKA-MPIfR Telescope in South Africa is ready for science operations

January 25, 2024

The journey into the golden age of radio astronomy continues with the SKA telescopes, which will become the largest radio telescope arrays on Earth in the coming years. The Max Planck Institute for Radio Astronomy (MPIfR) in Bonn has played an active role in their development over the past decades, and 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. To develop key technologies with unique scientific benefits, the MPIfR, together with 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. Here we report on the first light and the scientific readiness of SKAMPI.

Fig. 1: First light SKAMPI image of the Southern Sky at 2.5 GHz wavelength. The frame (in grey) shows the complete sky in galactic coordinates. The false colour image shows radio emission from the part of the sky which is accessible to the telescope in South Africa, in Galactic coordinates with the Galactic Centre position in the centre of the image. Besides radio emission from the Galactic centre (Sgr A), the bright radio galaxy Cen A, both Magellanic clouds and star forming areas in Orion and Vela show up in the image. — **Fig. 1:** First light SKAMPI image of the Southern Sky at 2.5 GHz wavelength. The frame (in grey) shows the complete sky in galactic coordinates. The false colour image shows radio emission from the part of the sky which is accessible to the telescope in South Africa, in Galactic coordinates with the Galactic Centre position in the centre of the image. Besides radio emission from the Galactic centre (Sgr A), the bright radio galaxy Cen A, both Magellanic clouds and star forming areas in Orion and Vela show up in the image.

© SKAMPI Team

**Fig. 1:** First light SKAMPI image of the Southern Sky at 2.5 GHz wavelength. The frame (in grey) shows the complete sky in galactic coordinates. The false colour image shows radio emission from the part of the sky which is accessible to the telescope in South Africa, in Galactic coordinates with the Galactic Centre position in the centre of the image. Besides radio emission from the Galactic centre (Sgr A), the bright radio galaxy Cen A, both Magellanic clouds and star forming areas in Orion and Vela show up in the image.

© SKAMPI Team

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 and technical commissioning such as system evaluation, radio-frequency-interference testing and performance testing took place until early 2022, leading to the SKA system design qualification documents published in 2022. Since then, developments were pursued setting up a framework to operate SKAMPI remotely and as a robotic system, integrating telescope operations with frontend and backend control, and synchronizing 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 for 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 large field of view, and thus fast sky coverage, with excellent polarization properties in order 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 is shown in Figure 1, demonstrating 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 a 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, as shown in Figure 2. 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 the establishment of a framework that will 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 so provide fast feedback of the observations and system performance. Soon we will start testing a fully automated system that includes the output of the automated analyses to manage the entire observations of a scientific programme."

Although much of the observing time on SKAMPI will be dedicated to large-scale internal science programmes, requests for observations will be open to the South African and German science communities, and there will also be an opportunity to set up an educational programme for schools and universities.

Fig. 2: First-light observations of the Vela pulsar with SKAMPI. The top panel shows the uncalibrated pulsar signal as its beam sweeps over the Earth. The bottom panel shows the same signal but now resolved in frequency. The 120-sec long observation spans the full S-band frequency range, from 1.75 to 3.5 GHz. — **Fig. 2:** First-light observations of the Vela pulsar with SKAMPI. The top panel shows the uncalibrated pulsar signal as its beam sweeps over the Earth. The bottom panel shows the same signal but now resolved in frequency. The 120-sec long observation spans the full S-band frequency range, from 1.75 to 3.5 GHz.

© SKAMPI Team

**Fig. 2:** First-light observations of the Vela pulsar with SKAMPI. The top panel shows the uncalibrated pulsar signal as its beam sweeps over the Earth. The bottom panel shows the same signal but now resolved in frequency. The 120-sec long observation spans the full S-band frequency range, from 1.75 to 3.5 GHz.

© SKAMPI Team

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Additional Information

MeerKAT: Built and operated by the South African Radio Astronomy Observatory (SARAO), the 64 dish MeerKAT is the largest radio telescope in the Southern hemisphere and one of two SKA precursor instruments based in South Africa. Located in the Karoo semi-desert, the radio telescope will soon be expanded with an additional number of dishes, in the context of the “MeerKAT+” project, jointly funded by SARAO and the Max-Planck-Gesellschaft (MPG) in Germany. The telescope will later be gradually integrated into SKAO's Mid telescope in South Africa.

SKAO: The SKA Observatory (SKAO) is an intergovernmental organisation bringing together nations from around the world. Its mission is to build and operate cutting-edge radio telescopes to transform our understanding of the Universe, and deliver benefits to society through global collaboration and innovation. The Observatory has a global footprint and consists of the SKAO Global Headquarters in the UK, the SKAO’s two telescopes at radio-quiet sites in South Africa and Australia, and associated facilities to support the operations of the telescopes. Once in operation, the SKAO will be one global observatory operating two telescopes across three continents on behalf of its member states and partners.

SKAMPI: The SKA-MPIfR telescope has been designed by the SKAO’s international DISH consortium, involving institutions in 10 countries and manufactured by CETC54 in China and OHB Digital Connect GmbH (former MT-Mechatronics GmbH). It was implemented by the Max Planck Institute for Radio Astronomy (MPIfR) and the South African Radio Observatory (SARAO), and funded by the Max Planck Society (MPG) and SARAO. The performance of the antenna structure has been verified by SARAO and MPIfR. SKAMPI is hosted by the SARAO, which is a facility of the National Research Foundation, an agency of the Department of Science and Innovation in South Africa.

Several of SKAMPI’s subsystems, including the Dish Fibre Network, Single Pixel Feed Controller, and the Helium and Vacuum services were developed, supplied and integrated by SARAO. SARAO assisted with the update and replacement of Sumoto Heavy Industrues (SHI) compressor which was the modified Off-The-Shelf compressor with the Oxford Cryo System (OCS) compressor which is production type model. Although, SARAO does not perform planned maintenance on this dish but it continues to support with corrective maintenance on cryogenics and vacuum systems.

SKAMPI’s capabilities give an impression of what will be realised with the full SKA-Mid telescope, comprising 133 SKA dishes and 64 MeerKAT dishes.

Acknowledgement: SKAMPI, the SKA-MPG prototype telescope, is a facility of the Max-Planck Society (MPG) and was established with the assistance of the South African Radio Observatory (SARAO). It is jointly operated and maintained by the Max Planck Institute for Radio Astronomy (MPIfR) and SARAO. This research was made possible with the support of the MPIfR and SARAO.