The Ariel mission will observe spectroscopically around 1000 exoplanets to further characterise their atmospheres. For the mission to be as efficient as possible, a good knowledge of the planets’ ephemerides is needed before its launch in 2028. While ephemerides for some planets are being refined on a per-case basis, an organised effort to collectively verify or update them when necessary does not exist. In this study, we introduce the ExoClock project, an open, integrated and interactive platform with the purpose of producing a confirmed list of ephemerides for the planets that will be observed by Ariel. The project has been developed in a manner to make the best use of all available resources: observations reported in the literature, observations from space instruments and, mainly, observations from ground-based telescopes, including both professional and amateur observatories. To facilitate inexperienced observers and at the same time achieve homogeneity in the results, we created data collection and validation protocols, educational material and easy to use interfaces, open to everyone. ExoClock was launched in September 2019 and now counts over 140 participants from more than 15 countries around the world. In this release, we report the results of observations obtained until the 15h of April 2020 for 120 Ariel candidate targets. In total, 632 observations were used to either verify or update the ephemerides of 84 planets. Additionally, we developed the Exoplanet Characterisation Catalogue (ECC), a catalogue built in a consistent way to assist the ephemeris refinement process. So far, the collaborative open framework of the ExoClock project has proven to be highly efficient in coordinating scientific efforts involving diverse audiences. Therefore, we believe that it is a paradigm that can be applied in the future for other research purposes, too.

Ariel 任务将通过光谱观察大约 1000 颗系外行星，以进一步表征它们的大气层。为了使任务尽可能高效，在 2028 年发射之前需要对行星的星历有充分的了解。虽然一些行星的星历正在逐个进行改进，但有组织的努力来共同验证或更新它们必要时不存在。在这项研究中，我们介绍了 ExoClock 项目，这是一个开放、集成和互动的平台，目的是为 Ariel 将观察到的行星生成一份确认的星历表。该项目的开发方式是为了充分利用所有可用资源：文献中报告的观测、空间仪器的观测以及主要是地面望远镜的观测，包括专业和业余天文台。为了方便没有经验的观察者，同时实现结果的同质化，我们创建了数据收集和验证协议、教育材料和易于使用的界面，对所有人开放。ExoClock 于 2019 年 9 月推出，现在有来自全球 15 个以上国家的 140 多名参与者。在此版本中，我们报告了截至 2020 年 4 月 15 日对 120 个 Ariel 候选目标的观测结果。总共使用了 632 次观测来验证或更新 84 颗行星的星历。此外，我们开发了系外行星特征目录 (ECC)，这是一个以一致方式构建的目录，以协助星历细化过程。迄今为止，ExoClock 项目的协作开放框架已被证明在协调涉及不同受众的科学工作方面非常有效。因此，我们相信它是一个可以在未来应用于其他研究目的的范式。