Revolutionizing our understanding of young stars and protoplanetary disks from the ground and space

Determining stellar and accretion properties of young stars is vital to better understand the ultimate evolution of planet-forming disks, and to constrain the processes leading to the formation of planets. One of the best methods for this is using spectroscopic analysis of UV continuum excess and activity related emission lines. The recent ESO/VLT Large Program PENELLOPE, in synergy with the HST public survey ULLYSES, are providing a unique opportunity to investigate such young stars via multi-wavelength, high resolution spectroscopy. These surveys provide a pivotal foundation for further synergies with JWST and ALMA. For the first time, we have near-simultaneous flux-calibrated spectra from UV (HST, X-Shooter) through optical (ESPRESSO, UVES) to the K-band in the near-IR (X-Shooter) of over 80 young stars. These data allow us to constrain stellar accretion models, calculate precise stellar parameters, explore both short and long term accretion variability, and investigate relationships between activity closest to the star and the extended structure of protoplanetary disks. They will be fundamental in future observation planning from the new and next generation of telescopes. I will present the main results obtained from these programs thus far, highlighting the legacy value of these surveys to better decipher the conditions of disk evolution and planet formation