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LOFAR Development Newsletter December 2022

Fantastic news! The ILT Board approved the purchase of LOFAR2.0 hardware for 52 of the 54 stations (including BG and IT) plus spare parts. The ILT Board also agreed to collaboratively purchase hardware for the remaining two stations such that they can be upgraded as soon as funding is in place. On top, HBA subracks are purchased for 10 future dual-beam stations. For LOFAR, this is the best possible outcome and a great achievement of the ILT, especially considering the increased hardware prices on the market since the start of the project.

It’s already December. Undoubtedly 2022 has been a year with many successes: TMSS has gone into production, the DANTE project has kicked-off, the LOFAR2.0 hardware for the stations and the timing distributor have been tendered, and the LOFAR2.0 test stations are showing excellent results. In doing so, we also learned a lot about the way we work together and how we can do that even more smoothly in the future. An excellent result and an solid basis for the challenges that await us in 2023.

Happy reading!

Wim van Cappellen

CEntral Processor Vision Towards 2030

André Gunst    Boudewijn Hut

One of the strengths of LOFAR is its flexibility in producing data products in various ways and at different stages. During the 10+ years of LOFAR operations various systems and functionalities have been “grown” to the system to support multiple kinds of black-ops use. Since, many of the systems in Groningen need to be replaced over the coming years and to deal with the astronomer ambitions for the current decade a vision towards 2030 for the CEntral Processor system (the current Cobalt2.0, CEP4, data ingest machinery and network) has been drafted and will be proposed to the ILT board. Realizing on one hand a system which delivers standard data products in a robust way to the Science Data Centre and on the other hand a system which is very flexible to support specific use cases often results in contradictory requirements. To overcome this, the envisaged system will be optimized for the following three key areas:

  1. Quality: Turn LOFAR into a robust data producing machine delivering fully automatic standard high-quality data products to the SDC.
  2. Innovative: Leverage the flexibility of LOFAR to deliver non-standard data products from anywhere in the data chain to accommodate dedicated and specific science (examples cosmic rays, pulsars with DRAGNET, EOR with DAWN export, transient detection with AARTFAAC or GLOW)
  3. Explorative: Facilitate expert users to (1) explore early and discover new science, (2) improve and characterize the instrument and (3) for commissioning and test new pipelines/functionalities

As can be seen in the figure these areas are covered by

  1. Standard Correlator & Beamformer Production System, for delivering data in a robust way to the SDC. The ambition is to do most, or if possible all, processing in real-time, such that data transport between sub-systems and buffers are minimized.
  2. Guest, dedicated Science Systems to serve dedicated science users for innovative specific science areas
  3. Explorative expert commissioning & experimenting system: for one off science experiments, characterizing the system and commissioning the system


Arno Schoenmakers

Early October we have taken a next major step in the Station Development Test program. We have moved the hardware that we used in DTS-Outside to a real LOFAR Station, CS001. For the station development project this marked the start of the LOFAR2.0 Test Station (L2TS) phase 1 tests. It is called phase-1 as we still have a limited number of antennas connected. At this moment, we are using 4 high-band RCU2s to connect 6 HBA tiles, and 6 low-band RCU2s to connect 9 LBA antenna. We are planning to use different sets of antennas to test different aspects of the system.

So far everything is looking great at L2TS. Together with colleagues from Telescope Operations the CS001 cabinet was cleared of most of the existing LOFAR1 hardware. Then the LOFAR2.0 hardware was carefully transported from Dwingeloo to the field and placed in the now empty cabinet. Power, network, antennas were connected and within a day or two the team managed to set up a working system again. Ever since that was done, the system has run almost flawlessly which gives us good confidence that we can run the entire test program without major hurdles.

The L2TS tests focus on aspects that we could not test at Dwingeloo due to much worse RFI situation so close to our building, and on aspects for which we need different geographical configurations of HBA and LBA antennas than we have at Dwingeloo, related to beamforming functionality. In December we will have a L2TS test results review, as we had in September for DTS-Outside. After that we wait for the additional hardware to arrive to extend L2TS to a fully equipped LOFAR2.0 test station, which will start L2TS phase-2. We expect that to happen in March 2023.

Pictures of the LOFAR2.0 hardware after placement in the cabinet of CS001
Figure 1: Pictures of the LOFAR2.0 hardware after placement in the cabinet of CS001.


Figure 2: Plots showing the passage of satellites over the CS001 station’s HBA antennas. The circles are the sky as seen by each tile (North is up). The tile numbering of 0-5 is arbitrary. Six tiles have been connected and each has been set to a different tile pointing (depicted by the blue crosses in the circles) The colour density of the dots indicate the signal strength as measured by each tile projected on the satellite position at the time of measurement. These plots shows that the ‘analog pointing’ of the HBA tiles is working well in LOFAR2.0.

Procurement LOFAR2.0 hardware

Nico Ebbendorf

Over the last few months, we have been working hard on the LOFAR2.0 procurement. All electronic modules for the LOFAR2.0 sub-racks are included in a single European tender process as described in previous newsletters. This process ended last month and we have found three manufactures that will carry out the module production. The tender process for the White Rabbit network equipment is also finalized and orders will start soon. Meanwhile, the ILT board came with a great decision to upgrade all the current LOFAR stations to LOFAR2.0! This means that the production numbers are confirmed. With this outcome, we will be able to place an order for the purchase of all electronic components required for the stations upgrade now. We accept that we will take a risk since we have not yet tested a complete (L2TS) station. However, by doing so, we are able to manage the long component lead time and getting control over the project costs despite the very unstable component market which we have reported in this newsletter before. Nevertheless, the production will be carried out in two phases in order to mitigate technical risks. First, we will have a null-series production for the upgrade of two stations. The PCB layouts for this production run will be based on the outcome of L2TS (mid 2023). With two stations converted, we can carry out more in-depth system tests before starting a large series production of all the LOFAR2.0 hardware. Between the two production runs we have the opportunity to make small design adjustments. With this scheme, we trust to have the best solution for controlling the various project risks.

There are still more modules and parts to be procured such as the mechanical components, power supplies cables and more. These will be handled during the next months. So, no time to sit back and relax (yet).

A pipeline to automate the creation of value-added catalogues for LoTSS

Rafaël Mostert

The LOFAR imaging surveys accelerate research in astronomy by presenting well-calibrated, ready-to-use Stokes-I and Stokes-V images.
Accompanying these images with extensive source catalogues makes the value proposition for astronomers within and outside of the collaboration even higher.
The source catalogues list which radio components make up each single radio source within the survey, which optical or near-infrared source is the most likely corresponding host-galaxy, and even include forced-photometry estimates on these hosts.
The catalogues will get even better in the coming years as forced-photometry will be complemented by spectroscopic photometry via the WEAVE-LOFAR survey.

Specifically, for the LOFAR (wide-area) Two-metre Sky Survey (LoTSS), these catalogues are created by combining radio-blob-detection software (PyBDSF) with crowd-sourced annotations ( for the radio source component association and optical host galaxy identification.
This process works but can take days per observation.
By combining three existing projects into a single pipeline, we attempt to create a pipeline that automatically generates a value-added catalogue for any LoTSS observation within an hour, without requiring human (or crowd-sourced) intervention.
The first part of the pipeline, created by Lara Alegre et al. 2022, uses a gradient boosting classifier to judge whether a radio component can simply be cross-matched to an overlapping optical source, or whether it requires association to other radio components and/or more involved methods to find the optical host. The second part of the pipeline, created by Rafaël Mostert et al. 2022, uses a Fast region convolutional neural network to associate radio source-components. The third part of the pipeline, created by Bonny Barkus et al. 2022, traces the highest intensity ridge line of a radio source to find the most likely corresponding optical host-galaxy.
Depending on the assessment of the performance and quality of the outputs generated by the pipeline, it will allow us to run experiments on the LoTSS data that were previously impractical.
The project is supervised by Huub Rottgering and assisted by Huib Intema from the Leiden Observatory.


Carla Baldovin

The project DANTE (Development of an Advanced HBA Frontend) kicked off its activities in May of this year with the goal of allowing LOFAR High Band Antenna’s (HBA) to continue delivering science in the LOFAR2.0 era.

This will be achieved by the two following objectives:

  • To deliver the design of a new frontend board for the HBA; this will be achieved in phase 1, running now. This step is necessary due to the increasing failures of the HBA after +10 years of continuous operations.
  • To deliver the design of the electronics to enable the HBA to produce two beams that can be operated independently and in parallel; development to start in a second phase.

In October 10 and 11, the team of DANTE reached its first main milestone: the preliminary design review (PDR). The panel composed of W. van Cappellen (chair), A. Gunst, M. Norden, F. Perini and R. Witvers had the task of assessing the status of the design by looking at different aspects such as requirements, architecture, schematics, costs, risks, planning. We had open and constructive discussions during these two days, including a live demo of the prototype boards that have been produced so far.

At the end of the meeting, the panel determined that the team is ready to move forward with the next step in the development. In addition, the panel gave several recommendations that the team is now converting into actions. This positive outcome gives us a boost of motivation to continue working on this exciting development.

A big compliment to all team members: A. van Duin, B. Hut, H. Meulman, J. Herrewijnen, L. Goudbeek, M. Ruiter, P. Kruger, and S. Damstra.


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