I concluded the previous newsletter by saying that I miss you. Well, I still do! At the same time, I would like to make you a huge compliment on how you managed to adapt to working from home! The uncertainty, in the beginning, has disappeared and all teams managed to continue their work. The last 2 months were busy as usual, and the results are great as witnessed by the achievements presented in this Newsletter.
I am looking at the future with confidence, even when realizing that this pandemic probably changed our way of working permanently. Please persevere in your creativity and flexibility in adapting to the situation. In the meantime, the holiday season has kicked in. I wish all of you who planned a leave, a very relaxing time in good health.
Wim van Cappellen.
Transparency as a tool to ensure successful system integration
The documentation of a design should be simple. It should be clear how one part relates to another, and how the design is build up. So far, in LOFAR2.0 each group or project uses a different structure to keep information. Only for formal moments, like design reviews, it is baselined and placed in a central system. Up until that moment, it is unclear where information is kept, leading to duplication, or even contradictory information.
We are all thrived to make the LOFAR2.0 upgrade an enormous success and deliver a telescope that works for the astronomer. In other words, all parts in the telescope need to work together, allowing the astronomer to make discoveries happen. Contradictory or duplicate design information will make that much harder.
The solution is to set up a transparent and uniform documentation structure across the program. In the last months, the station project adopted a structure in which each piece of information has one logical and findable location. The new structure proved to work very well, and the program team decided to adopt it for the program as a whole! Anyone who needs to know about a certain aspect in the LOFAR2.0 design can find the piece of information that is actually being used by the development team. This way we greatly reduce the chance on malfunctions. So by this new structure, the design as a whole will improve, making it more efficient -and fun- to work on LOFAR2.0.
The architectural design document of the SDC and LOFAR2.0 interaction has been finished and the review process by reviewers from LOFAR2.0, SDC and the Science Support group is started. Both systems are currently heavily intertwined and the design document gives a clear view of the cut on many aspects. The goal of both systems in the near future is very distinct:
- LOFAR2.0 is seen as a data capturing telescope delivering standard data products
- The SDC system
- provides services for users to access the data
- is used to request LOFAR2.0 observing time
- (re-)processes the data further
One of the outcomes of the split is that the scientist only has an interface with SDC and not LOFAR anymore. SDC takes care of the selection of proposals submitted and lets the user generate so-called scheduling sets, which defines the (repetitive pattern of) observations which need to be done to accomplish the goals of the proposal. The scheduling set is used as input for LOFAR. During data taking the status of observations is reported back to the SDC and finally, the data products with associated metadata are ingested in SDC. On the highest business flow level represented in Figure 1, the split is defined between the business management and daily management of the telescope.
First RCU2-board in production at ASTRON
The cooperation with INAF has produced a first design of the new RCU2. The design has been simulated and verified by some test PCBs. Prototypes are currently being manufactured in Italy (the RF section) and at ASTRON (the digitization section). We hope to obtain these prototype boards soon and include it in the Lab Test Station that we are assembling right now.
More Design and Prototyping activities
Hardware development for LOFAR2.0 is at full throttle, not only RCU2 board development, but other activities are running to deliver new hardware for the LOFAR2.0 Station. Parts of the Power, Clock and Control (PCC) board have been designed and are being layed-out or are in production. The LOFAR2.0 Midplane (LMP), connecting the RCU2’s with the UniBoard2’s and the PCC inside a subrack, has been designed. Finally, the modelling of the new subrack holding all the new components has started. Investigations into proper cooling of all equipment housed by the cabinets is ongoing, with current emphasis on the possibility to cool the FPGAs on the UniBoard2s by air, instead of using liquid cooling.
To control and monitor the new hardware, the LOFAR2.0 Station will receive a completely new software stack. The architecture and design of that is quite different than that of the LOFAR1 station software. The new software will control and monitor most parts of the station, directly impacting the station's dynamic behaviour. It is therefore of the utmost importance that the desired behaviour is worked out in detail during the design process. The team has done a great effort to improve the design with respect to LOFAR1 and Apertif, based on years-long experience, especially with LOFAR1.
Little progress has been made in Telescope Manager. It is expected that this continues to be the case, at least until after the Summer Holidays. Alignment with other subsystems is taking place where necessary, e.g. with TMSS and TD. The definitive scope of TM still needs to be fleshed out, pending the final decisions on the LOFAR2.0-SDC split.
In the LOFAR Newsletter from last September, the Uniboard2 procurement was announced. We followed the European procurement procedure and finally the selection committee awarded Neways B.V. Leeuwarden for the production of the Uniboard2. They provided an excellent quotation with full conformity with the requirements and within the expected budget. Neways B.V. was also involved with the development and production of the previous version of the Uniboard and we feel confident to start the partnership with them for the new Uniboard2 production. Two prototype Uniboard2s are on order now and assembly will start as soon as the design is ready. The prototypes will be followed by an order for four boards as the “null-series production” to fine-tune the design and the production. Full production is planned in the second half of 2022.
On May 13, LOFAR4SW hosted its Users Workshop via zoom. The organisation of the workshop was led by our partners at CBK-PAN (Poland), responsible for the dissemination and outreach activities.
The meeting had 54 participants from a wide range of organisations and expertise; from space weather scientists to forecasters and commercial space weather service providers. The goal of the meeting was to gather input from the users about how LOFAR data can be used in space weather science and monitoring.
At the beginning of the meeting, the LOFAR4SW consortium presented an introduction to the project, its main goals and activities. Then followed a set of shorter presentations from the different use cases developed during the project for Solar, Heliospheric, and Ionospheric domains.
The second part of the meeting was dedicated to invited presentations from a small group of invited participants. The speakers provided very useful input by presenting their ideas on how LOFAR data could improve their domain of expertise. The final session was dedicated to a guided discussion focusing on specific topics proposed by the organisers that included the prioritisation of the use cases.
In summary, the workshop was very constructive and useful. The invitees actively participated in the discussions and showed real interest in many of the capabilities that the LOFAR4SW system could offer. The project is now processing the results from the workshop and use this information to finalise the use case prioritisation.
COBALT2.0 phase 2
Since the last newsletter, phase 2 of COBALT2.0 has started implementing new functionality. At the time of writing, the team has completed three sprints and is currently working on the fourth. The first sprint was taken up by an intensive, but highly successful knowledge transfer process. We are now finalizing the first addition to the COBALT2.0 code, which we expect to fully test, commission and roll-out in the next couple of weeks. This will include a minor update to the DAL and associated Interface Control Documents.
The first deliverable will add the ability to redigitize beamformed data products to lower their bit depth, allowing the formation of more tied-array beams within the bandwidth limit to our storage cluster. In the course of this work, we explored the relative error introduced, which turned out to be minor except when clipping, as shown in the image.
Finally, we welcomed a new member to our team, Steven van der Vlugt, who has started to familiarise himself with LOFAR and the COBALT2.0 system. Even in these challenging times, we've been able to make good progress, and remain on schedule. Phase 2 of the COBALT2.0 project will run until May 2021 in three 3-month intervals and will focus on several functional improvements to the correlator and beamformer system in LOFAR.
TMSS (Telescope Manager Specification System) will be a brand-new software application for the specification, administration, and scheduling of LOFAR observations. Its realisation is crucial, as 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. This is being realized by a team of software engineers and telescope scientists who are very committed to make the project a success. TMSS is an important component of the Telescope Manager of LOFAR2.0, the system that will control all aspects of the telescope, including proposal handling, observation execution, and system monitoring.
Since the past newsletters, the TMSS project has made progress in various areas. Thanks to the addition of frontend developers to the SCRUM team, we have explored different technologies for the developments of the TMSS web interfaces. This led to the adoption of ‘PrimeReact’ as a framework for further implementations. The collection of user stories for GUI’s development is well underway and will steer further developments in this area. After the first light of TMSS in April 2020, the project is ready to achieve a new milestone, consisting of the execution of a scheduling block (the combination of observations, pipelines and quality assurance plots) at the next sprint review meeting at the end of June. In the background, the formulation of user’s stories for the implementation of the DUPLLO science use cases and the dynamic scheduling system is progressing steadily.
We are currently discussing when TMSS will be switched to production and used as the only specification and scheduling platform for LOFAR. Moreover, we are preparing a sketch for the second phase of the projects, which may realize the support for more science use cases as well as additional operational efficiency improvements.
Searching for exo-aurorae
LOFAR’s deep, all-sky survey LoTSS is providing a treasure chest of data with many applications. Harish Vedantham, Joe Callingham, Tim Shimwell (and others!) have been cross-matching LoTSS radio sources with nearby stars detected through their optical emission. This has allowed them to identify interesting new cases of stellar radio emission, which is already surprising and novel, as well as cases where that emission might be generated by a host star interacting with an exoplanet in close orbit.
In a recent Nature Astronomy paper (see paper and commentary), they argue that the star GJ1151 may be showing aurorae powered by an orbiting exoplanet (see animation and ASTRON press release). The artist’s impression shown here depicts a stream of plasma flowing along the magnetic field-lines of GJ1151. Near the polar regions of the star, the plasma emits radio waves before crashing into the star to produce aurorae.
Astronomers are interested in studying similar systems because it potentially teaches us about the environments of exoplanets, and how those are influenced by the activity of the host star. That has important consequences for understanding habitability in the Milky Way. This topic is a key scientific goal for the DUPLLO upgrade of LOFAR because such systems are expected to become even brighter at very low radio frequencies, and the combined LBA+HBA images could prove critical in discovering them.
A widefield sub-arcsecond image of the Lockman Hole field
Frits Sweijen, Reinout van Weeren, Huub Rottgering
One of the aims of LOFAR2.0 is to survey a large fraction of the sky at sub-arcsecond resolution. Central to this is the question of whether one can calibrate the ILT’s full field of view.
Here we demonstrate a direction-dependently calibrated image of the international station field of view out to its FWHM. This image of the Lockman Hole field was created from a single 8-hour observation over a 121-168 MHz bandwidth. Roughly 250 000 core hours were required. It covers just over 7 square degrees at a resolution of approximately 0.4’’. Direction dependent calibration solutions were derived in 44 directions. These solutions were interpolated into screens and applied during imaging using the newly developed IDG algorithm in combination with WSClean. The included image compares LoTSS (contours) with the ILT (colour).
Efforts by the long baseline team of the survey key project chaired by Leah Morabito and Neal Jackson continue to further understand and advance high-resolution imaging with LOFAR.