LOFAR2.0 Newsletter September 2021

Boudewijn Hut    André Gunst

Bringing it all together

For all the LOFAR upgrades planned, the goal is to early integrate sub-systems. From there on the system evolves further. For this a number of milestones have been defined and they are referred to as delta System Reviews (dSR). Each dSR has a specific focus. The upcoming dSR1 has as focus to integrate the developed Cobalt2.0 functionality in the LOFAR system, such that the science users can exploit its new features. For each of the delta System Reviews, the following steps are followed to bring new functionality to production:

1. Involved sub-systems incorporate the required functionality
2. Sub-systems are integrated with each other to deliver an operable solution
3. System acceptance tests
4. Science commissioning

Upcoming delta System Reviews are the integration of the Timing Distributor (TD), integration of the LOFAR2.0 station with CEP and the integration of the LOFAR2.0 station with the Telescope Manager (TM). In this way we are bringing all the sub-systems with their upgrades together in the LOFAR telescope.

Arno Schoenmakers

We are gradually receiving the prototype boards we set out for manufacturing. The first two Uniboard2C prototypes have been received, tested and approved. In addition, we have received the Power distribution boards (APSPU, Antenna Processing Subrack Power Unit) and the Clock and Control boards (APSCT, Antenna Processor Subrack Clock distribution and Translator board). See the pictures below for an image of these boards.

The largest uncertainty we face is when we will receive the Mid-plane boards (LMP2) which connect the RCU2 boards with the Uniboards, APSCT, APSPU in a subrack. At the moment of writing, the circuit boards are scheduled for production in Vietnam. Vietnam, however, is in a rigorous lock down situation due to COVID. It is unclear when this lock-down will be lifted so that the production of the boards can start. Alternative production locations are being investigated, but so far, we could get no guarantees for a rapid delivery, yet. Clearly, this delay affects our plans for assembling two complete DTS subracks and for when we can start to test these subracks in DTS.

Preparations for testing are continuing nevertheless. Both firmware and software control and monitoring are being prepared for DTS, using the still existing Lab Test Station (LTS). Subband statistics can already be acquired by the station software, and soon cross-correlation statistics as well, created by the built-in correlator functionality of the firmware.

Over the summer, we have used DTS to characterize the cooling capacity of the station cabinet. For this, we added increasing amounts of heat in a DTS cabinet, using dummy subracks equipped with electric heaters. This enabled us to mimic the energy dissipation of actual equipment in a subrack. We measured day and night cabinet temperatures in various environmental conditions and outside temperatures, in order to better understand the effects of sun load and wind convection around the cabinet.

The recorded data is currently being analysed. LOFAR2.0 will produce more heat than LOFAR1.0 in each subrack, so understanding the cooling capacity is vital to predict the expected amount of down time during a hot summer like in 2019 or 2020. We expect results of this analysis by half September.

Last of all: to keep track of events happening in this project, please follow our news blog posts in Confluence, either through this link: https://support.astron.nl/confluence/display/L2M/DTS+NEWS or by joining the #lofar2-general Slack channel in the ASTRON slack workspace. Non-ASTRON readers may have to request permission to access our news blog.

Carla Baldovin

The scope of the Timing Distributor upgrade is to rollout a single clock for all LOFAR stations in the Netherlands. After the Station and Timing Distributor Preliminary Design Review in 2019, the TD upgrade project continued in a development path parallel to Station.

After many months of hard work involving planning, documentation, meetings, decisions, more planning, tests, analysis, etc. TD had the Critical Design Review (CDR) as a hybrid meeting on August 26-27. The panel of reviewers included: André Gunst (ASTRON – chair), Menno Norden (ASTRON), Maaijke Mevius (ASTRON), and Jeroen Koelemeij (VU Amsterdam).

According to the reviewers:

“The panel is confident in the team’s competence to deliver the timing distributor solution for LOFAR2.0.”

During the meeting we had constructive discussions in an open atmosphere. We highly appreciate the work and enthusiasm from the reviewers.

The panel will deliver a complete report shortly after the meeting. As a team, after enjoying this moment, we are ready to tackle the issues raised by the experts and continue working to deliver an improved timing solution for LOFAR.

A big compliment to the team for the effort made to reach this point, we now have a clear way forward to complete the Timing Distributor upgrade!

Carla Baldovin

Over the past months, there has been intense work for the LOFAR4SW team in the different partner institutes. In particular, WP5: Hardware design – led by ASTRON and in collaboration with Paris Observatory, Nançay group – completed the production of the hardware components to build an HBA dual beam tile. These include: the HBA frontend, HBA beamformer boards, RF summation board and power distribution boards (the summation and power distribution boards are modifications to the current LOFAR boards). All the building blocks for a new HBA tile were assembled and verified in laboratory conditions. The tests performed on power, RF, control, show a good performance of the hardware and overall compliancy with the requirements.

This is a major step towards the completion of the LOFAR4SW design, which ultimate goal is to deliver the full conceptual and technical design for creating a new leading-edge European research facility for space weather science. The new HBA tile will be capable of producing two beams, to allow parallel astronomy and space weather observations. Credits go to the team at ASTRON: Mark Ruiter, Paulus Kruger, Jeroen Herrewijnen, Albert van Duin, Gerda Sikken and Nançay: Sangitana Rokotozafy Harison, Severin Barth, Bruno Da Silva, and Stephane Bosse.

Currently, ¼ of a dual beam tile is assembled in the Dwingeloo test field and it’s producing spectra with 2 beams. In the coming weeks the full tile will be assembled, to study the behavior under real environmental conditions.

The full LOFAR4SW design – that encompasses, science use cases, architecture, hardware, software, operations and governance model – will be assessed at the Critical Design Review in a few weeks from now (21-23 September 2021).

Sander ter Veen

ASTRON is developing TMSS (Telescope Manager Specification System), which is a brand-new software application for the specification, administration, and scheduling of LOFAR observations. It will enable the required support for LOFAR2.0 use cases, while also streamlining LOFAR operations and improving the adaptability and maintainability of software for future extensions.

During the past two months, we have focused on getting TMSS ready to be run in production. We have added support for LBA imaging observations, responsive telescope functionality, improved the quality assessment workflow and worked on user permissions and reporting. We are now adding all the strategies needed to run in production and finishing the final parts needed to go live. The progress of the project can be tracked online through the TMSS infographics, which were developed with the intent to keep our stakeholders informed about the up-to-date status of the implementations.

We plan to install TMSS on the production system during September, and will start running some and soon all production observations with TMSS. The user documentation has largely been written and training of users is ongoing.

Sander ter Veen has taken over from Roberto Pizzo as product owner. We thank Roberto for his contributions to the project.

Christian Groeneveld

In a recent press release, a team of scientists from across Europe present their work on using LOFAR to achieve sub-arcsecond resolution images from galaxies at low frequencies.
In particular, we have been able to achieve high resolutions using LOFAR LBA (https://arxiv.org/abs/2108.07286). At these frequencies, ionospheric effects are so severe that this limits our ability to calibrate the most distant international stations.

In this paper, we present six images of bright radio sources (3C 196, 3C 225, 3C 273, 3C 295, 3C 298 and 3C 380). These sources are all relatively compact and bright at low frequencies, which is critical for our ability to calibrate the longest baselines. We performed the calibration in three steps: first we corrected the instrumental effects of the LOFAR stations using our observation of 3C 196 and a high-resolution model from André Offringa. In the next step, we calibrate only the core stations for each of our six sources. The core stations are then ‘locked’ and combined into a ‘superstation’. Finally, we calibrate each source against a simple model of the source, in order to calibrate the remote and international stations. This allows us to achieve a resolution of around 1 arcsecond at frequencies between 80 and 30 MHz, which is an order of magnitude better than previous work. In turn, we can use this incredible gain in resolution to map aged electrons in radio galaxies and clusters in great detail.

Although we have shown that it is possible to use the full ILT for LBA work, there is still plenty of room for improvement. Long baseline work would benefit significantly from additional stations, especially at baselines bridging the gap at a few 100 km between the Dutch stations and the distant ILT stations. In the near future, LOFAR2.0 will allow us to observe both LBA and HBA simultaneously, which will allow us to bootstrap LBA calibration with HBA observations.