Merging European and Rubin Observatory efforts to probe the dark universE (MEROPE)

The nature of dark matter and dark energy stands out as the most tantalizing and unresolved problem in modern cosmology. The Vera C. Rubin Observatory is the new-generation optical ground-based facility designed to shed light onto this cosmic puzzle by observing the effects of weak- and strong-gravitational lensing on thousands of galaxies in the sky. As with every new facility, ultimate performances are never achieved at the telescope’s first light, the first scientific image of the sky, but they require meticulous fine-tuning, optimization, and calibration of many instrumental and atmospheric effects. This proposal has a dual nature, including both instrumentation and scientific investigations. The instrumentation work is focused on minimizing the Observatory’s instrumental systematic errors and developing reliable calibration techniques to disentangle these optical artifacts from the intrinsic cosmological shear of weak- and strong-lensing effects and astrometric signals. The control of these systematic errors will enable high-quality scientific results, carrying out cutting-edge early science works on many Rubin science cases. The proposed instrumental and scientific activities will sustain the Vera C. Rubin Observatory revolution of our knowledge of the cosmos in many fields of astrophysics, thanks to its unprecedented field of view coupled with deep photometric sensitivity. The Rubin Observatory is a US-led observing facility with In-kind participation from 28 countries, with strong European participation, making it the ideal playground for a big international, multicultural, and inclusive environment that will play a major role in the astrophysics of the next decade. This project represents a unique opportunity for the training of engineers and scientists, for creating new connections and strengthening existing worldwide networks among the astronomical community, nourishing a generation of young researchers for the upcoming extremely large telescope era.