Subjects: Geosciences >> Space Physics Subjects: Physics >> Geophysics, Astronomy, and Astrophysics Subjects: Astronomy >> Galaxy and Cosmology submitted time 2024-06-02
JI Jianghui
LI Haitao
ZHANG Junbo
LI Dong
FANG Liang
WANG Su
DENG Lei
CHEN Guo
LI Fei
DONG Yao
LI Baoquan
GAO Xiaodong
XIAN Hao
Abstract： The Closeby Habitable Exoplanet Survey (CHES) employs state-of-the-art, high-precision astrometry and positioning technology at the microarcsecond level in space. Its primary objective is to conduct a thorough survey of approximately 100 FGK-type stars within the Sun’s proximity (within 10 parsecs), with the goal of detecting potentially habitable Earth-like planets or super-Earths. This pioneering mission involves a detailed census of habitable planets, providing intricate information on their numbers, true masses, and three-dimensional orbits. Notably, CHES marks a historic milestone as the inaugural international space exploration mission exclusively dedicated to the study of terrestrial planets within the nearby habitable zone. CHES’s payload features a cutting-edge optical telescope with a 1.2 m aperture, a field of view measuring 0.44°×0.44°, and a focal length of 36 m. The telescope utilizes a coaxial three-mirror TMA optical imaging system. Impressively, CHES is designed with a positioning measurement accuracy of 1 μas, solidifying its status as the most precise space exploration project globally in terms of positioning accuracy. To achieve the detection objectives of CHES, it is essential to refine and further substantiate the scientific goals through comprehensive argumentation. Overcoming three key technological challenges is crucial: advancing optical systems for large field of view, developing high-quality space telescopes with minimal distortion; breaking through measurement technology for stellar separations at the 10–5 pixel level; and achieving high stability in satellite system attitude control and thermal control precision. CHES stands on the threshold of groundbreaking discoveries, with the exciting prospect of revealing 50 Earth-like planets. This announces a significant leap forward in China’s space science exploration technology.
Subjects: Geosciences >> Geodestics submitted time 2019-04-10
Abstract： " GNSS-R is a new promising remote sensing technique, which utilizes the reflected signals of GNSS constellation to remotely sense the ocean or land surface. At present, most of the existing research are based on the experimental observations, few theoretical studies have been carried out. This paper has developed a fully polarization GNSS-R delay Doppler map for land geophysical parameters study. This theoretical model was based on the ocean surface GPS scattering model, after the modifications, it has been used for the land surface. As for the calculations of land geophysical parameters (bare soil and vegetation), random surface scattering model and the first order radiation transfer equation model were used. Effects of bare soil and vegetation parameters on the delay Doppler maps were simulated. In order to use the polarization information for backward inversion, our developed theoretical model has the ability of fully polarizations calculations, i.e. RR, LR, HR and VR pol. This theoretical model is a mechanism tool for the data explanation of space borne mission, experimental campaign design, data simulations and the backward inversion algorithm development. "
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