It's been a month since Euclid embarked on its journey into the cosmos. Thales Alenia Space’s engineering team is still working tirelessly on the crucial commissioning phase at ESOC, conducting final performance tests and checking configurations that were only possible once the telescope was in orbit. They have to make sure that everything is working properly before officially handing over the mission to the scientists.

© Thales Alenia Space \ Emmanuel Briot

We had the pleasure of speaking with two esteemed members of the Euclid Consortium who’ve been working on this project for over a decade: Andrea Cimatti, professor at the University of Bologna and Head of the Department of Physics and Astronomy since 2021, and Michel Berthé, Project Manager at the CEA’s Department of Astrophysics. They shared with us the challenges they will have to overcome to carry out their research and analysis of the huge amount of data collected by Euclid.

Andrea Cimatti & Michel Berthè

© Thales Alenia Space \ Andrea Cimatti \ Michel Berthè

How long you have been involved in the Euclid project? Which scientific aspect interests you most?

Andrea: I’m a founding member of the Euclid project. My involvement dates back to 2007 when I led one of the two projects submitted to ESA in response to the ESA Cosmic Vision 2015-2025 call for proposals for medium-class missions. The proposed mission was called SPACE, and the other one (with Alexandre Refregier as Principal Investigator) was DUNE. ESA then merged the two missions into Euclid. All in all, I’ve been involved in Euclid for 16 years. I’m a member of ESA’s Euclid Science Team and, within the Euclid Consortium, I’m one of the two Italian representatives on the EC Board, along with Roberto Scaramella from INAF. I also coordinate the “Galaxy and AGN Evolution” science working group in collaboration with Jarle Brinchmann and Emanuele Daddi.

My main scientific interest is the interface between cosmology and galaxy formation and evolution. More specifically, I’m interested in using galaxies as evolutionary probes to apply constraints on cosmological parameters and study the relationship between luminous and dark matter. Apart from my official roles, I’m also actively involved in promoting Euclid in universities to encourage student interest and I engage with the general public through special events, articles and books.

Michel: I was the Euclid Consortium Lead Advisory and Coordination Support, responsible for overseeing the technical aspects and monitoring consortium program schedules. I’m also the project manager for all CEA activities on Euclid, mainly focused on developments for the VIS (Focal Plane, PMCU electronics) and NISP (cryo-mechanisms) instruments. I’ve been involved with Euclid for 12 years. As an engineer, I have no direct scientific role on the mission, but I’m thrilled to be able to contribute to a mission that will help us better understand the as yet unknown forces and energies that drive the evolution of the universe.

© ESA

During its six-year mission, Euclid will collect a huge amount of data. Is humanity and the scientific community ready to handle all this data, and how are you preparing to analyze such a massive amount of information? Do you expect any scientific discoveries within the first year after launch?

Michel: Indeed, the Euclid mission is set to collect an unprecedented volume of data. Over the last ten years, the Euclid Consortium has focused on organizing, designing and developing the Science Ground Segment, responsible for processing this massive volume. The processing will take place at eight Science Data Centers in Europe and the United States. Due to the sophisticated processing required to convert raw data into information that can be interpreted in a cosmological context, careful planning and validation with simulated data are essential.

As part of the Euclid Consortium, our role involves not only processing the data but also communicating the results to a broad audience, even when dealing with complex physics like Einstein’s theory of relativity. While we anticipate significant scientific results in the first year after launch, it’s crucial to meticulously carry out the planned six years of sky mapping to meet our scientific objectives with the expected level of accuracy.

Andrea: Euclid is a revolutionary mission. The amount and diversity of data – petabytes worth, while imaging in the visible and near-infrared and spectroscopy in the near-infrared – makes Euclid truly unique. Some 10 billion sources will be observed, out of which more than one billion will be used for weak lensing, with about 30 million galaxy redshifts. Besides the spacecraft and its instruments, a key part of the Euclid mission is the Science Ground Segment, which includes the ESA Science Operations Centre (SOC) and the Euclid Consortium Science Ground Segment (EC SGS).

In addition, an array of national Science Data Centers will allow us to process the data, monitor the instruments and provide datasets from ground-based telescopes to complement the Euclid data. The Euclid Consortium members are developing algorithms and tools to optimize the data analysis and maximize the scientific return. The data collected during the first year of the mission will be critical, enabling us to run the codes on real data (after a decade of simulated data), evaluate their quality, assess performance and obtain initial scientific results. This will be a key to further optimizing the analysis of all data and therefore maximizing the accuracy of the cosmological parameters that are the main objective of the mission. After the first year, major results are also expected in the vast realm of “legacy science” (e.g. reionization, galaxy formation and evolution).

What are some of the most significant challenges you expect to face, and how do you plan to address them?

Michel: In order to achieve our scientific objectives, we need to be able to map the sky with very high accuracy and maintain very stable observing conditions during the six-year mission. This requires maintaining a high degree of stability for the telescope and spacecraft, of course, but above all in terms of temperatures, optical alignment and instrument pointing.

Andrea: In cosmology, one of the most significant challenges is retaining full control of systematic effects to generate the most accurate and reliable results. It’s well known that each cosmological investigation is affected by its own systematic errors. During the development of Euclid over the last decade, the scientific and data analysis groups worked together to investigate all the potential systematic effects, and to identify how to minimize and control them for each area. Remember that the key advantage of Euclid is that its dataset will allow us to tackle a variety of cosmological investigations at the same time (weak lensing, galaxy clustering, galaxy clusters, strong lensing, cross-correlations with the CMB, etc.). This makes Euclid a complete “experiment”, combining cosmology and fundamental physics. Thus, the combination of different investigations will be essential to further increase the accuracy and reliability of the results. The high quality and stability of space-based data will also play a decisive role here, and the synergy with the ground-based data will further boost the impact of the results in several fields of cosmology and astrophysics. The Euclid Consortium worked very hard well in advance, and is ready for this exciting challenge!

We’ve just embarked on this immersive journey into how Euclid will help scientists make groundbreaking discoveries. Stay tuned, because our journey with Andrea and Michel doesn’t end here. Next time, they’ll share insights on the collaboration between science and industry and how this remarkable mission will revolutionize our understanding of the Universe.