EChO科学案例
The EChO science case
摘要：
近2000颗系外行星的发现揭示了一个意想不到的行星种群多样性。迄今为止的观测表明，我们的太阳系当然不能代表银河系中的行星总数。因此，迫切需要解决的关键科学问题是：系外行星是由什么组成的？为什么行星是这样的？与太阳系相比，是什么原因导致了观测到的异常多样性？EChO（系外行星特征观测台）被设计为一个专门的过境和日食光谱调查任务，能够在其四年的任务寿命内观测大型和多样化的行星样本。EChO可以瞄准超级地球、类海王星和类海王星行星的大气层，这些行星位于F到M型宿主恒星的非常热到温带（行星温度为300 K-3000 K）。在接下来的十年里，几个新的地面和空间过境调查将上线（例如NGTS，CHEOPS，TESS，PLATO），这将特别关注寻找明亮的附近系统。目前的快速发现速度将使目标清单在EChO发射前的几年内得到进一步优化，并使数百颗行星的大气特征成为可能。将卫星放置在L2层提供了一个寒冷和稳定的热环境，以及一个大的视野，以便对随机分布在天空中的目标进行有效的时间紧迫的观测。1米级的望远镜足够大，可以达到必要的分光光度精度。由于EChO的高稳定性和专用设计，其光谱覆盖范围（0.5-11微米，目标16微米）和SNR将能够非常准确地测量数百颗系外行星的大气成分和结构。
英文摘要：
The discovery of almost 2000 exoplanets has revealed an unexpectedly diverse planet population. Observations to date have shown that our Solar System is certainly not representative of the general population of planets in our Milky Way. The key science questions that urgently need addressing are therefore: What are exoplanets made of? Why are planets as they are? What causes the exceptional diversity observed as compared to the Solar System? EChO (Exoplanet Characterisation Observatory) has been designed as a dedicated survey mission for transit and eclipse spectroscopy capable of observing a large and diverse planet sample within its four-year mission lifetime. EChO can target the atmospheres of super-Earths, Neptune-like, and Jupiter-like planets, in the very hot to temperate zones (planet temperatures of 300K-3000K) of F to M-type host stars. Over the next ten years, several new ground- and space-based transit surveys will come on-line (e.g. NGTS, CHEOPS, TESS, PLATO), which will specifically focus on finding bright, nearby systems. The current rapid rate of discovery would allow the target list to be further optimised in the years prior to EChO's launch and enable the atmospheric characterisation of hundreds of planets. Placing the satellite at L2 provides a cold and stable thermal environment, as well as a large field of regard to allow efficient time-critical observation of targets randomly distributed over the sky. A 1m class telescope is sufficiently large to achieve the necessary spectro-photometric precision. The spectral coverage (0.5-11 micron, goal 16 micron) and SNR to be achieved by EChO, thanks to its high stability and dedicated design, would enable a very accurate measurement of the atmospheric composition and structure of hundreds of exoplanets.
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