CTAO organisation and Swiss participation

In the 1980’s, after almost 20 years of developments, X- ray astronomy moved from PI led experiments to observatories open to the scientific community at large. This evolution led to the enormous success of X-ray astronomy which is presently one of the major branches of astronomy. Ten years ago, the hard X-ray-MeV community followed the same route and now, it is the turn of the GeV–TeV community, where the ambition of CTAO entered the ESFRI Roadmap thanks to the strong convergence of the European and Intercontinental communities of high-energy astronomers and particle physicists. They share a clear vision to move from experiments such as H.E.S.S., MAGIC and VERITAS, which release only a small amount of high-level data, to an observatory structure serving a broad community.

For the first time, the intention to participate to the establishment of CTAO of the scientists in Switzerland appeared in the CHIPP document on the achievements of the CHIPP Roadmap 2005-2010, and clarified in the following 2018-2020 CHIPP Roadmap containing the Recommendation 6: “CHIPP recommends a further strengthening of ties with the CHAPS community, both scientifically and technically. As an instrument of common interest for both communities, Switzerland should secure access to CTAO at a level that is appropriate for the size of the Swiss researcher community interested in CTAO…”. This recommendation for a joint effort of the CHIPP and CHAPS for the establishment of Multi-Messenger Astrophysics in Switzerland with CTAO and gravitational wave infrastructures is repurposed in the Roadmap document 2025-2028. The size of the CTAO future users has ramped up to approach now 3% of the project and they are spread in the major institutes in Switzerland (UniGe, ETHZ, EPFL, UZH and Bern).

Despite this apparently small fraction, the Swiss scientists cover many responsibility roles. In 2007 the UZH, UniGe and ETHZ joined the CTA Consperience with silicon photomultipliers, that were adopted for the SSTs and SCTs. This work was mostly sustained by the competitive programs of SNSF Sinergia, FLARE and R’Equip and by the support of involved Institutes and Research Foundations, as Boninchi and Schmidheiny in Geneva.

In 2014 UZH, DESY and INAF funded the legal interim entity of the observatory, the CTAO GmbH which will be in operation to 2024. Prominently, Prof. Straumann of UZH covered the role of Managing Director of the CTAO GmbH from 2016 to 2018. Since then, CTAO is governed by a Council including the representatives of associated nations, advised by a STAC.

In Switzerland, CTAO joined the SERI Roadmap for large Research Infrastructures in 2016 and in fall of 2019, UZH transferred the share of votes to the UniGe. For the period 2021-2024, two Performance Agreements were signed with SERI, one coordinated by the UniGe on the LST, Data Pipeline and Preservation System (DPPS) and on the Array Control and Data Acquisition (ACADA) software of CTAO. Currently, the plans for the 2025-2028 period have been evaluated as Category A in the Swiss Roadmap process by the SNF and the project can guarantee the participation to the development of relevant software and hardware as in-kind contributions described in the next sections. CTAO will transit to an ERIC legal entity in Aug. 2023 (see schedule below) with 13 member and observer nations (Australia, Austria, Czech Republic, France, Germany, Italy, Japan, Poland, Slovenia, Spain, Switzerland, United Kingdom, the Netherlands) and the Intergovernmental Organisation ESO. The transition to the ERIC is an extremely important phase: Switzerland will initially join as a Founding Observer, and then it is extremely relevant that it joins as a full member to fully profit from the accession to the observation time of CTAO for long term. The schedule of the project is highlighted below with major milestones.

During the operation of CTAO, including the operation of one of the 4 CTAO off-site Data Centres in Switzerland, the allocation of the observation time, beyond the legacy time of CTAO for the Key Science Projects and the reserved time for various agreements with the hosting country (Spain) and the ESO, will be prioritised based on scientific excellence. For the first time in this field, CTAO will generate large amounts of data in part publicly accessible, allowing data mining in addition to targeted observation proposals. Other data will be accessible through policies and tools in use in the astronomical observatories based on the excellency of proposed science from the member states of the observatory. CTAO aims to emerge as a cornerstone in a networked multi-wavelength, multi-messenger exploration of the Universe. Proposals can be submitted to request normal observations, observations coordinated with other observatories, target of opportunity and will be selected based on scientific merit through a peer-review process.