一种新的探测器系统增益变化校准方法
A New Method for Calibration of Gain Variation in Detector System
摘要：
在凌日/日食观测期间，围绕晚型恒星运行的适居行星的凌日光谱学需要在波长之间具有较高的相对分光光度精度。分光光度计信号不仅受到由于波前误差引起的图像移动和变形的影响，而且还受到检测器系统中的电变化的影响。这些随时间变化的成分，耦合到过境信号，扭曲过境光谱的大气成分的测量。在这里，我们提出了一个新的概念，提高分光光度的准确性，通过校准的检测器系统中的时变成分，通过开发致密的光瞳光谱，提供多个光谱的恒星行星系统。由于被物体光曝光的一组像素（即，科学像素），像素到像素的变化可以通过平均操作被平滑，因此仅保留科学像素上的公共时间变化分量。此外，考虑到检测器平面与光瞳平面光学共轭，光瞳掩模可以完全阻挡进入残留像素的天文光。共同的时变分量重建与残留像素和减少到一个随机项。应用致密光瞳光谱仪与中红外探测器系统的大型空间低温望远镜，如起源太空望远镜，我们表明，该系统几乎实现光子噪声限制的性能和检测的吸收功能，通过透射光谱和二次日食的类地行星轨道M-型恒星在10 pc的60个过境观测。因此，所提出的方法有助于测量行星的可居住性和附近过境可居住候选人的生物特征。
英文摘要：
Transit spectroscopy of habitable planets orbiting late-type stars requires high relative spectro-photometric accuracy between wavelengths during transit/eclipse observation. The spectro-photometric signal is not affected only by image movement and deformation due to wavefront error but also by electrical variation in the detector system. These time-variation components, coupled to the transit signal, distort the measurements of atmospheric composition in transit spectroscopy. Here we propose a new concept for improvement of spectro-photometric accuracy through the calibration of the time-variation components in the detector system by developing densified pupil spectroscopy that provides multiple spectra of the star-planet system. Owing to a group of pixels exposed by the object light (i.e., science pixels), pixel-to-pixel variations can be smoothed out through an averaging operation, thus only common time-variation components over the science pixels remain. In addition, considering that the detector plane is optically conjugated to the pupil plane, a pupil mask can completely block astronomical light incoming into residual pixels. The common time-variation components are reconstructed with the residual pixels and reduced into a random term. Applying the densified pupil spectrograph with a mid-infrared detector system to a large space cryogenic telescope such as the Origins Space Telescope, we show that the system nearly achieves photon-noise-limited performance and detects absorption features through transmission spectroscopy and secondary eclipse of terrestrial planets orbiting M-type stars at 10 pc with 60 transit observations. Thus, the proposed method contributes to the measurement of planetary habitability and biosignatures of the nearby transiting habitable candidates.
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