光纤阵列太阳光学望远镜研究组知识库

相比于其他探测手段,行星的偏振探测能够提供更多有关行星表面以及大气的细节信息,而地球的偏振测量则有助于寻找系外类地行星以及对其大气和表面特征的鉴定.将地球看成一颗与其寄主星(太阳)可分辨但其自身圆面不可分辨的行星来研究其在太阳照射后辐射进入太空的偏振特性.采用PARASOL的670 nm(662.4 nm～677.4 nm)波段的观测结果,得到不同地表类型和云层的偏振度和反照率随散射角和相对方位角的变化,然后根据辐射偏振的Stokes参量可叠加特性,求得在90?散射角下,地球整体辐射的偏振度随自转的变化.结果发现:影响地球偏振的最大因素是海洋和云层,地球偏振度可以在18.6%到49%之间变化.由于气候变化导致的云层分布的随机性使得地球偏振度的变化具有快速多变的特点.揭示的这一特征有助于辨别系外类地行星.

Compared with other diagnostic techniques, the planetary polarimetry becomes more efficient to probe the details about the surface features of an exoplanet,and especially the polarimetry of our planet, the Earth, is useful to search for the Earth-like exoplanet. In this paper, the Earth is treated as a planet resolvable from its host star but its disk is unresolved. The data from the polarimeter boarding French satellite PARASOL are used to get the polarimetric results of 5 surface features as well as cloud within the band of 662.4–677.4 nm. The results are expressed in the curves which reflect the variations of linear polarization degree and albedo with the scattering and azimuth angles, respectively. Under the special case that the scattering angle is set to be 90 degrees, the polarization curves of the Earth in a rotation period are obtained.It is found that the polarization degree is mainly influenced by the ocean as well as the cloud, ranging from 18.6% to 49%. And due to the rapid climate change on the Earth,the polarization can be altered rapidly. This characteristic will help us to distinguish the Earth-like exoplanet from other types of exoplanets.