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Target RA (J2000): 348.949035644531 and deg Target Dec (J2000): -10.8496904373169 and deg Gaia GMag: 12.0 Programme ID: CH_PR140080 Programme Manager: LELEU PI of observing programme: Benz Title of programme: Axis 1 - Architecture of Resonant Chains (ARC) Abstract: Resonant chains are gold mines for fueling our understanding of planetary systems. The minute details of their architectures encode the history of their formation: the order of the capture of the planets in the chain (Delisle 2017) the local shape of the proto-planetary disc and its dispersal (e.g. Nesvorny et al 2022) and the long-term evolution of the system through tidal dissipation (e.g. Papaloizou et al 2018). The high multiplicity of these systems also makes them especially valuable to constrain our models of the formation of planetary systems (See Emsenhuber et al 2022 and other papers of the NGPPS series) since all the planets have to form in the same environment and the relative fragility of the configuration ensures that no violent evolution (e.g. close encounters/impacts) occurred after the dissipation of the proto-planetary disc (Leleu et al 2021). In addition the transit timing variations induced by the compactness of the systems allow for precise mass determination down to a few per cent in the case of Trappist-1 (Agol et al 2021). This allows an in-depth characterization of moderately insolated rocky planets and mini-Neptune with a precision which is rarely reachable through radial velocities enabling studies of their interiors and atmospheres. The brightness of the current targets of the program (Gaia band mag 11 for TOI178 12 for K2-138 8.4 for TOI1835) allows to combine RVs and photometric measurements. The two methods have a great synergy as TTVs allow for in-depth characte [truncated! Please see actual data for full text]