Exploring synergies between Twinkle and Ariel: a pilot study

Launching in 2027 and 2029, respectively, <i>Twinkle</i> and <i>Ariel</i> will conduct the first large-scale homogeneous spectroscopic surveys of the atmospheres of hundreds of diverse exoplanets around a range of host star types for statistical understanding. This will fundamentally transition the field to an era of population-level characterisation. In this pilot study, we aim to explore possible synergies between <i>Twinkle</i> and <i>Ariel</i> to determine for instance whether prior <i>Twinkle</i> observations can substantially inform the target selection and observing strategy of <i>Ariel</i>. This study primarily aims to encourage further investigation by both consortium communities by showing what a potential scientific synergy would look like on a promising scientific case that requires further exploration. For this aim, we select a small subset of 'cool' planets that are also particularly well-suited to be observed by <i>Twinkle</i> and therefore <i>Ariel</i>. By using representative noise estimates for both missions, we compute the number of visits required for an observation. Then, we simulate and retrieve transmission spectra of each target, assuming gaseous, H[Formula: see text]/He-dominated atmospheres and various atmospheric models to test different scenarios. For all candidates, we find that atmospheric parameters are generally retrieved well within 1-[Formula: see text] to input values, with <i>Ariel</i> typically achieving tighter constraints. We also find that retrieved values may depend on the tier when <i>Ariel</i> can achieve Tier 3 in a single visit, due to the information loss that may occur in binning. We demonstrate that for a small subset of cool gaseous planets, exploitable synergies exist between <i>Twinkle</i> and <i>Ariel</i> observations and <i>Twinkle</i> may very well provide a vantage point to plan <i>Ariel</i> observations. The true extent of the potential synergies, far beyond our considered sample, will be determined by the final target lists. Once Twinkle is operational and its performance is known, it could reliably inform Ariel's target prioritization and Ariel's capabilities which are already well-established can help define optimal targets and observational approaches for Twinkle. Therefore, further exploration of potential synergies is highly warranted especially after Twinkle is operational and Ariel's launch date approaches.