The Dwingeloo Test Station: a major milestone towards LOFAR2.0

BY PROF. JASON HESSELS (ASTRON)

A major upgrade to the Low Frequency Array (LOFAR) is now a step closer following the opening of the new Dwingeloo Test Station (DTS) in the Netherlands, which will test prototype software and hardware for LOFAR2.0.

LOFAR is a pan-European radio telescope that links tens of thousands of antennas across 10 partner countries, an enormous geographical span which allows it to make remarkably sharp images. The low-band antennas (LBA) and high-band antennas (HBA) provide a powerful view of the lowest radio frequencies visible from Earth: from 10- 240 MHz.

At the time of construction, the available computational power meant that it was only possible to use either the LBA or HBA antennas at any given time. With LOFAR2.0, it will be possible to use all the LOFAR antennas at once and to expand the field-of-view of the stations. This is made possible by an order-of-magnitude increase in the computing power at the LOFAR stations, as well as a new central computational “brain”, the COBALT2.0 correlator and beam-former. Furthermore, a new White-Rabbit-based clock distribution system is being installed such that there are no timing delays between the 38 Dutch LOFAR stations. [White Rabbit is a technology that provides extremely accurate (nanosecond level of accuracy) timing over the network. It can be used to provide timing to the antennas so that data from each receptor can be accurately timestamped. It is also being used by the SKAO for its telescopes.]

On 10 May, the Dwingeloo Test Station was ceremoniously opened. Located next to ASTRON, it is testing the entire LOFAR2.0 signal chain: from the antennas, through the new receiver boards and Uniboard-squared-based processing, all the way to the correlator and beam-former. This is a crucial step in the development process because it allows the prototype electronics, firmware and software to be tested before being rolled out to a full LOFAR station and then the entire array.

The team has already achieved the “first fringes” between test antennas [showing they can operate as an array], as well as multi-day stability tests with all LBA and HBA antennas observing simultaneously. This progress means the first full LOFAR2.0 station is on track for delivery by early 2023.

These enhancements are being implemented from 2021-2024, and together will provide a step function in LOFAR’s overall scientific capabilities. It will remain a unique and world-leading telescope, also accessing the largely unexplored spectral window below 50 MHz.

Early LOFAR2.0 science observations are planned to begin in 2025, affording ultra-wide-band, ultra-deep, ultra-highresolution observations. Among the many scientific goals for LOFAR2.0, such observations can track the history of star formation and galaxy evolution over cosmic time, as well as identify starplanet interactions in our own galaxy.

ABOVE: Compilation of pictures of the DTS Opening event on the ASTRON premises on 10 May 2022. The speakers (from top left to bottom right) are ASTRON director Prof. Jessica Dempsey; LOFAR2.0 Station Development Project Manager Arno Schoenmakers; and LOFAR2.0 Project Scientist Prof. Jason Hessels.

Photos courtesy of Adriaan Renting and Mark Ruiter (ASTRON).