Nulling interferometry: impact of exozodiacal clouds on the performance of future life-finding space missions
Nulling interferometry: impact of exozodiacal clouds on the performance of future life-finding space missions
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归零干涉测量：星外云对未来生命探索太空任务性能的影响
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发表时间：
2009
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通讯作者：
C. Stark
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作者：
D. Defrére;O. Absil;R. Hartog;C. Hanot;C. Stark
上下文地球大小的行星围绕着附近的恒星，这是第一次通过地基径向速度和天基凌日观测被发现。这一里程碑为能够直接探测来自这些行星的光的仪器的定义开辟了道路，其中生物特征识别是主要目标之一。在这方面，欧洲航天局（欧空局）和美国国家航空和航天局（美国航天局）都认为调零干涉测量法是最有前途的技术之一。然而，研究遥远行星的能力将取决于目标恒星可居住区中的系外黄道尘埃的数量。目标。我们评估的影响，exozodiacal云的红外调零干涉仪在艾玛X-阵列配置的性能。研究的第一部分专门研究光盘亮度对在使命寿命期内可通过光谱学进行调查和研究的目标数量的影响。在第二部分中，我们解决了光盘中的非对称结构的影响，如团块和偏移，可以潜在地模仿行星信号。方法.我们使用设计和验证的DarwinSIM软件来研究天基调零干涉仪的性能。该软件已被改编为处理exozodiacal光盘的图像，并计算相应的解调信号。结果对于具有2米孔径望远镜的标称使命结构，可以容忍中心对称的比太阳黄道云密度约100倍的黄道外尘埃盘，以便在使命寿命期间调查至少150个目标。考虑到模拟的共振结构所产生的类地行星在1 Au围绕太阳一样的星星，我们表明，这种可容忍的尘埃密度下降到约15倍的太阳黄道面上的系统的密度，并减少与光盘倾角。结论.虽然圆盘亮度只影响积分时间，但团块或偏移的存在更有问题，可能会妨碍行星检测。根据碎片盘结构的最坏情况设想，可容忍的外黄道尘埃密度上限约为太阳黄道云密度的15倍。这就提供了我们需要在外黄道盘上达到的典型灵敏度，以便为未来的类地行星定性飞行任务的科学方案做准备。
Context. Earth-sized planets around nearby stars are being detected for the first time by ground-based radial velocity and space-based transit surveys. This milestone is opening the path toward the definition of instruments able to directly detect the light from these planets, with the identification of bio-signatures as one of the main objectives. In that respect, both the European Space Agency (ESA) and the National Aeronautics and Space Administration (NASA) have identified nulling interferometry as one of the most promising techniques. The ability to study distant planets will however depend on the amount of exozodiacal dust in the habitable zone of the target stars. Aims. We assess the impact of exozodiacal clouds on the performance of an infrared nulling interferometer in the Emma X-array configuration. The first part of the study is dedicated to the effect of the disc brightness on the number of targets that can be surveyed and studied by spectroscopy during the mission lifetime. In the second part, we address the impact of asymmetric structures in the discs such as clumps and offset which can potentially mimic the planetary signal. Methods. We use the DarwinSIM software which was designed and validated to study the performance of space-based nulling interferometers. The software has been adapted to handle images of exozodiacal discs and to compute the corresponding demodulated signal. Results. For the nominal mission architecture with 2-m aperture telescopes, centrally symmetric exozodiacal dust discs about 100 times denser than the solar zodiacal cloud can be tolerated in order to survey at least 150 targets during the mission lifetime. Considering modeled resonant structures created by an Earth-like planet orbiting at 1 AU around a Sun-like star, we show that this tolerable dust density goes down to about 15 times the solar zodiacal density for face-on systems and decreases with the disc inclination. Conclusions. Whereas the disc brightness only affects the integration time, the presence of clumps or offset is more problematic and can hamper the planet detection. Based on the worst-case scenario for debris disc structures, the upper limit on the tolerable exozodiacal dust density is approximately 15 times the density of the solar zodiacal cloud. This gives the typical sensitivity that we will need to reach on exozodiacal discs in order to prepare the scientific programme of future Earth-like planet characterisation missions.