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Target RA (J2000): 207.526169 and deg Target Dec (J2000): -40.83580 and deg Gaia GMag: 9.615 Programme ID: CH_PR240017 PI of observing programme: Chakraborty Title of programme: Accurate and precise characterisation of the HIP 67522 system in the presence of significant stellar variability Abstract: Young planets are excellent laboratories to test planet formation and evolution pathways. However the accurate characterisation of parameters like the radius of the planet is limited by the enhanced activity of the host star. The impact of features like unocculted and occulted active regions is a growing challenge in the era of high-precision photometry and transmission spectroscopy and better characterisation of these features is now more vital than ever for the correct interpretation of atmospheres on exoplanets. Here we propose to precisely characterise the HIP 67522 system a 17 Myr Solar-like star exhibiting significant stellar activity and one of the youngest planet-hosting stars discovered to date. The HIP 67522 system consists of one confirmed transiting hot Jupiter (planet b) and an unconfirmed outer planet candidate (planet c). To characterise this key young system we aim to: i) obtain an accurate and precise radius measurement for the known transiting planet (planet b) by quantifying the effect of stellar activity on its transit depth and ii) confirm the candidate exoplanet (planet c) by following up the most likely period aliases of its two known transits. While accurately measuring the radius of planet b is vital for testing different planet formation and evolution models for hot Jupiters confirming planet c will make this the youngest multi-planet transiting system ever discovered making this a very compelling system to be observed by CHEOPS. [truncated! Please see actual data for full text]