The Euclid project

Cristobal Padilla


Euclid is a mission for the European Space Agency (ESA) Cosmic Vision (CV) 2015-25 programme to explore how the Universe evolved over the past 10 billion years to address questions related to fundamental physics and cosmology on the nature and properties of dark energy, dark matter and gravity, as well as on the physics of the early universe and the initial conditions which seed the formation of cosmic structure.

INTRODUCTION

The Euclid mission, part of ESA’s Cosmic Vision 2015-25 program, aims to explore the Universe’s evolution over the past 10 billion years. It seeks to understand dark energy, dark matter, gravity, and the early Universe’s initial conditions. To achieve this, Euclid will survey 14,500 deg² of the sky, capturing billions of celestial objects. Its high-resolution images and spectroscopic data will help analyze gravitational lensing effects and the 3D distribution of galaxies, significantly improving cosmological measurements, including neutrino mass and the state equation of cosmology. Launched on July 1, 2023, via a Falcon 9 rocket, Euclid reached Lagrange Point 2 (L2), successfully operating its visible imager (VIS) and near-infrared photometer/spectrograph (NISP). After commissioning, the mission started full-scale observations in February 2024, delivering unprecedented imaging and spectroscopy quality for deep-space exploration.

2024 Activities

Throughout 2024, the group has remained actively engaged within the Euclid consortium, working to analyze the data and contribute to the mission’s scientific output. Two PhD students are focusing on key aspects of data exploitation. One has developped a method to determine the photo-z distribution by cross-correlating redshift measurements with spectroscopic redshifts. This approach will help validate the n(z) distribution and identify potential biases, a critical step in extracting cosmological parameters from Euclid’s first data release. The method has been successfully applied to the DES survey and also the the Euclid Flagship simulation (the best available) and two scientific papers are underway.The other student is employing unsupervised machine learning techniques to denoise images and measure galaxy shear, a fundamental parameter in the weak-lensing signal of the Euclid project. This has resulted in an in-depth study on how the galaxy shear is measured in Euclid, making comparisons with the different methods. A complete pipeline is being developed to have it ready to run in the first Data Release in 2026.