Written by: Jürgen Knödlseder, Chair, CTA Consortium

Originally the CTA Consortium had planned to meet for its biannual meeting in Sofia, Bulgaria, but due to the COVID-19 pandemic it moved to a virtual gathering to share information and results. For the first time in history, the CTA Consortium meeting was organised as a full online meeting. The meeting was expanded to almost two weeks, from 13 to 22 May, so that sessions were limited to a few hours per day. In total, about 500 Consortium members registered for the online meeting with a peak attendance of about 270 people for a single session (see screen shot below that was taken during one of the plenary sessions).

As usual, the meeting started with parallel sessions during the first few days, followed by plenary sessions and closed by a Consortium Board meeting on the last day. While feedback on the online meeting format was very positive, people regretted the lack of informal gatherings during the coffee breaks and evenings that usually foster the interactions between colleagues. All plenary sessions were recorded, providing those who could not connect the possibility to replay the meeting. This is particularly useful for a world-wide Consortium such as CTA, with members distributed over many different time zones.

On the technical side, a highlight of the meeting was the announcement of the detection of TeV emission from the Crab nebula with the Schwarzschild-Couder Telescope prototype (pSCT). The pSCT is a prototype of a mid-sized telescope that is being developed by an international team under the leadership of our U.S. colleagues. The detection of the Crab nebula presents an important milestone for the project and demonstrates the feasibility of an innovative concept that has the potential to significantly improve the angular resolution of CTA. Other highlights of the meeting were the status reports of the Medium-Sized Telescope (MST) and Small-Sized Telescope (SST) sub-consortia that have organised to provide the MSTs and SSTs for CTA. Together with the already existing sub-consortium for the Large-Sized Telescopes, all telescope classes are now covered, and the provision of telescopes as in-kind contributions to CTAO is being organised.

Excellent progress was also reported by the Science Working Groups. The development of Consortium papers is progressing well, with two papers currently under final review by the Consortium. The multi-wavelength and multi-messenger coordination is also taking shape, moving now from the identification of CTA’s needs to the securing of access to data. The Analysis and Simulations Working Group reported on the development of analysis pipelines and their application to first real data from prototype telescopes. To improve the performance of event reconstruction and classification, the use of deep learning methods is also being explored. The planning of the next large-scale Monte Carlo simulation dubbed “Prod5” is basically finished, and the production recently began. Finally, a new task group was set up to address the still open questions related to the Instrument Response Functions of CTA.

The project also reported important progress during the meeting, with the cost book review completed and its approval now achieved during the June CTAO Council meeting. The CTAO Council has furthermore approved the deployment of five MSTs on the CTA-North site as pathfinder telescopes, paving the way for a gradual build-up of the array. Critical Design Reviews (CDRs) for the MST telescope and cameras are planned later this year, and an engineering review for the SST is scheduled for this summer. First steps towards the definition of a science plan for the construction phase were also presented.

During its meeting, the Consortium Board discussed issues related to Consortium publications, the improvement of the IT support for the Consortium activities, a low-carbon charter for Consortium members, and future Consortium meetings. Due to the uncertain situation related to the COVID-19 pandemic, it was decided to also hold the next Consortium meeting in the second semester of 2020 as an online meeting. Hopefully, the situation resumes to normal in 2021 allowing again for in-person meetings. The decisions on the meetings next year will be taken once the evolution of the COVID-19 situation has become more clear.