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Target RA (J2000): 229.838119506836 and deg Target Dec (J2000): 29.206169128418 and deg Gaia GMag: 9.72 Programme ID: CH_PR140065 Programme Manager: WILSON PI of observing programme: Benz Title of programme: Axis 1 - Solidifying Planet-Star Composition Links by Studying Why the Internal Structures of Planets Across the Galaxy Vary (YGAL) Abstract: Terrestrial planets form through the accretion of building blocks from dust grains to proto-planets. Heavier components sink and form metallic cores whilst pebbles from beyond snow lines deliver volatiles influencing atmospheres or water on Earth-like planets. Understanding the composition of planetary ingredients is vital. Planetary refractory elemental abundances mirror stellar values the Earth is a devolatised piece of the Sun. If this is universal we would expect a diversity in internal structures and atmospheres of planets orbiting metal-diverse stars. This is currently not well investigated however in recent years tantalising evidence has emerged for metallicity-driven trends in the physical characteristics of super-Earth and sub-Neptune exoplanets. These first pieces of evidence might be pointing towards chemically-diverse formation scenarios impacting the internal structures of planets however this is currently unclear as there are very few well-characterised small planets around metal-poor stars. Therefore this program will refine the radii of a handful of key planets around Galactic thick-disk metal-poor host stars to an unprecedented level in order to solve the current mysteries that we are just starting to unravel. [truncated! Please see actual data for full text]