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DUPLLO opens low-frequency window on the Universe

A €3,450,000 NWO Investment Grant Large has been awarded to ASTRON by the Netherlands Organisation for Scientific Research (NWO) in order to build and deploy DUPLLO: the Digital Upgrade for Premier LOFAR Low-band Observing. DUPPLO will greatly enhance the sensitivity and discovery potential of the Low Frequency Array (LOFAR) at the lowest radio frequencies visible from Earth. In doing so, it will enable deep observations through an unexplored window on the Universe.

Published by the editorial team, 28 September 2018

Astronomy studies electromagnetic radiation produced by cosmic sources. Different frequencies of the spectrum – from low-energy radio waves, like observed with LOFAR, up to high-energy gamma-rays – provide complementary information about the Universe and its constituents, including diagnostics of diverse physical processes. LOFAR is opening one of the last unexplored regions of the spectrum – very low radio frequencies.

The LOFAR high-band antennas (HBA: 110-240 MHz) enable sky images to be made with a sensitivity and resolution that far exceed the previous state-of-the-art. To name only a few examples, this has led to new insights into: the composition of cosmic rays, the electrodynamics of pulsars, the energetics of galaxy clusters, and the properties of the interstellar medium in our Milky Way. The LOFAR community has developed the innovative techniques required to calibrate these data, accounting for disturbances from the Earth’s ionosphere, and are now ready for the next challenge and opportunity: applying this expertise to develop the hardware and software needed to push LOFAR to lower frequencies and thereby exploit the full scientific promise of the LOFAR low-band antennas (LBA: 10-90 MHz).

DUPLLO is a major upgrade to LOFAR that will enable pioneering astrophysical research using the absolute lowest radio frequencies visible from Earth. Through improved collecting area and calibration, we will increase LOFAR’s LBA imaging sensitivity by a factor of roughly 5, while simultaneously pushing to lower frequencies (< 50 MHz) and maximizing the image fidelity. This will be achieved by

  1. doubling the number of active LBA antennas,
  2. installing a centralized high-precision clock distribution system, and
  3. using joint LBA+HBA antenna data to accurately model and remove ionospheric disturbances, which are strongest at low frequencies. This requires the development of substantially more sophisticated calibration techniques, and a major hardware enhancement to the LOFAR station electronics.

“Thanks to the DUPLLO upgrade, LOFAR will be able to give us our best-ever view of the Universe using the lowest-frequency radio waves we can observe from Earth. That is going to deliver answers to many current open questions in astronomy, but what excites me most are the excellent prospects that LOFAR will discover something completely new and unexpected,” says DUPLLO Project Scientist dr. Jason Hessels.

The new system is designed to address a broad range of fundamental scientific topics, including:

  • The formation and evolution of the earliest massive galaxies, black holes, and protoclusters and their influence in shaping the Universe.
  • The nature of galaxy clusters and the steep-spectrum radio sources that they host, including the influence of magnetic fields, shocks, and turbulence. These probe the most energetic processes since the Big Bang.
  • The Milky Way galaxy, including the topology of its magnetic field, `missing’ supernova remnants and ultra- steep-spectrum radio pulsars that can be used to probe the physics of ultra-dense matter.
  • The magnetospheric properties of exoplanets, by detecting super-Jupiters, and the potential habitability of planetary systems orbiting magnetically active host stars.
  • The composition of high-energy cosmic rays.
  • The structure and dynamics of the Earth’s ionosphere.
  • The discovery of new types of radio sources that radiate predominantly at the lowest frequencies.


An overview of how DUPLLO provides a major enhancement to the LOFAR telescope. DUPLLO will triple the processing power of the LOFAR stations, which will enable all antennas to be used at once during observations. DUPLLO also provides a high-precision clock signal that will keep all the stations in tight sync. Together with advanced calibration algorithms to correct for distortions caused by the Earth’s ionosphere, the DUPLLO upgrade will increase LOFAR’s sensitivity to ultra-low-frequency radio waves by a factor of roughly 5. This opens up a range of exciting scientific opportunities in studies that span from our own solar system out to the early stages of the Universe. 


LOFAR – developed by ASTRON and (inter-)national partners – is the world’s largest and most sensitive low-frequency radio telescope. It is a network of geographically distributed antenna stations, each containing hundreds of `low-band’ (LBA) and `high-band’ (HBA) dipole antennas. LOFAR stretches across Europe, from Ireland to Poland, with a dense `core’ in Exloo, 38 stations distributed throughout the Netherlands, and 13 additional stations located in the 6 partner countries that have joined the project since its inception.

Download the DUPLLO Factsheet here.



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