ESA’s Euclid Mission: The first year of operations

René Laureijs, Euclid project scientist at the European Space and Technology Centre (ESTEC) in the Netherlands, supports the science communities engaged in space-research projects and missions developed by European Space Agency (ESA).

“I started working on Euclid in the early days, when the proposals for a European dark energy mission were evaluated for further assessment,” says Laureijs. “Later I became the mission’s project scientist, being ESA's interface with the Euclid community and the general science community for scientific matters. I closely collaborated with the Euclid project team responsible for the development of the mission, and now I work together with the operations and science ground segment teams, to ensure the timely release of the data products.”

What led to your interest in astrophysics?
The real trigger was a visit to a Zeiss planetarium, when I was 14. I realised that observing from the Netherlands was not easy — our weather is cold and rainy — and I started reading astronomy books, leading me to a fascination in astrophysics.

What do you see as the most important aspect of your work at this time?
The objective of a project scientist is to maximise the scientific output of the mission. Since the moment Euclid started collecting astronomical data, it should be ensured that these data contribute to new scientific results. The delivery of the Euclid data products to the scientific community requires oversight and a lot of organization.

What is most exciting or surprising about your work? What are some of the challenges?
It is gratifying to see that the Euclid mission is meeting the performance requirements we envisaged from the beginning. The exciting part is seeing the raw data from the satellite transformed into astrophysical information such as images and spectra. Euclid has already generated truly spectacular images and plenty of new science. The challenge is to understand and cope with the in-orbit performances, which might have an impact on the operations and calibration of the data.

What are some of the big picture questions the Euclid mission addresses?
The big picture question is related to the dark universe: what is the nature of dark matter and dark energy contributing to 95% of all the mass in the Universe? Euclid can provide accurate measurements of the accelerated expansion of the Universe over 10 billion years of cosmic history.

The accelerated expansion led to the postulation of dark energy. From the growth of cosmic structures observed both in luminous and dark matter, Euclid should also provide an accurate test of general relativity on cosmic scales.

The Euclid mission launched on 1 July 2023. What have we learned about the Universe in these initial months of the mission?
A few weeks after launch we started with the Early Release Observations (ERO) program not only to showcase Euclid’s capabilities, but also to enable the earliest scientific investigations with Euclid. The observations were proposed by the Euclid community and cover almost all scales in the Universe, ranging from nearby star-forming regions in the Milky Way to distant clusters of galaxies. We detected so-called rogue planets down to a few Jupiter masses, we studied the properties of intra-cluster globular clusters, we mapped the distribution of intra-cluster light in a galaxy cluster tracing the dark matter, and much more. The first 10 scientific papers from the ERO programme were submitted to a refereed journal in May 2024.

What do you see as the future of missions such as Euclid? What would you like to see?
Euclid is a high-precision cosmology survey mission. If Euclid meets its performances during its nominal mission lifetime of six years, then Euclid will remain one of its kind, similar to other ESA surveys like Planck or GAIA. Euclid will collect large samples of new classes of objects, which can be followed up with ground- and space-based observatories such as the James Webb Space Telescope.

What would you like attendees to learn from your talk at SPIE Astronomical Telescopes + Instrumentation?
Even though Euclid is a cosmology mission, its capabilities enable studies in many fields of astronomy. Euclid will generate a detailed a three-dimensional map of the extra-galactic sky, eventually covering an area of one-third of the sky. The data will become public and are expected to be the starting point for many new scientific investigations.