飞行中photometry提取PLATO目标：探测太阳系外行星的最佳孔径
In-flight photometry extraction of PLATO targets: Optimal apertures for detecting extrasolar planets
摘要：
欧空局的PLATO空间任务致力于揭示和描述新的太阳系外行星及其宿主恒星。该任务将包括一个非常大的视野，根据最终的观测策略，它有可能调查多达100万颗恒星。航天器的遥测预算无法处理以正确的节奏传输如此巨大的恒星样本的单个图像，因此必须制定适当的战略来进行机载数据简化。我们采用孔径测光法来产生恒星在飞行中的光变曲线。因此，我们的目标是找到掩模模型，优化减少的数据的科学性能。我们考虑了三种不同的孔径模型：二元掩模，加权高斯掩模，加权梯度掩模，通过一种新的直接方法计算出最低的信噪比。采用了一种创新的标准来选择不同的面罩型号。我们指定为最佳的模型提供最佳的折衷之间的灵敏度，以检测真正的和虚假的行星过境。我们根据模拟的信噪比和阈值交叉事件的频率确定了最佳模型。我们的研究结果表明，虽然二进制掩模在统计上提出了百分之几的噪声信号比加权掩模相比，这两种策略在检测合法的行星过境非常相似的效率。然而，当涉及到避免来自污染星的虚假信号时，二元掩模在统计上收集的污染通量比加权掩模少得多，从而允许前者在$7.1σ$处提供高达$\sim$ 30\%的虚假凌日特征。我们提出的用于选择孔径的方法已被证明对于确定能够提供接近最大行星产率并大幅减少误报发生的掩模模型是决定性的。
英文摘要：
The ESA PLATO space mission is devoted to unveiling and characterizing new extrasolar planets and their host stars. This mission will encompass a very large field of view, granting it the potential to survey up to one million stars depending on the final observation strategy. The telemetry budget of the spacecraft cannot handle transmitting individual images for such a huge stellar sample at the right cadence, so the development of an appropriate strategy to perform on-board data reduction is mandatory. We employ aperture photometry to produce stellar light curves in flight. Our aim is thus to find the mask model that optimizes the scientific performance of the reduced data. We considered three distinct aperture models: binary mask, weighted Gaussian mask, and weighted gradient mask giving lowest noise-to-signal ratio, computed through a novel direct method. An innovative criterion was adopted for choosing between different mask models. We designated as optimal the model providing the best compromise between sensitivity to detect true and false planet transits. We determined the optimal model based on simulated noise-to-signal ratio and frequency of threshold crossing events. Our results show that, although the binary mask statistically presents a few percent higher noise-to-signal ratio compared to weighted masks, both strategies have very similar efficiency in detecting legitimate planet transits. When it comes to avoiding spurious signals from contaminant stars however the binary mask statistically collects considerably less contaminant flux than weighted masks, thereby allowing the former to deliver up to $\sim$30\% less false transit signatures at $7.1σ$. Our proposed approach for choosing apertures has been proven to be decisive for the determination of a mask model capable to provide near maximum planet yield and substantially reduced occurrence of false positives.
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