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Advanced Topic: A Moon-Based Imaging of Earth’s Surface
Published in Kun-Shan Chen, Radar Scattering and Imaging of Rough Surfaces, 2020
To define the Moon-based SAR’s imaging geometry as shown in Figure 10.1, it is critical to obtain the accurate position vectors of the ground target and SAR system under a spatial reference system in a specified time coordinate [12,13]. The Barycentric Dynamical Time (TBD) is used for providing the coordinate time scale [14,15]. Then, the Moon-based SAR and ground target are mapped to the same reference frame through a series of coordinate conversions.
Error analysis of exterior orientation elements on geolocation for a Moon-based Earth observation optical sensor
Published in International Journal of Digital Earth, 2020
Huadong Guo, Hanlin Ye, Guang Liu, Changyong Dou, Jing Huang
As the description above, the transformation between the geolocation coordinates (pe) and the image coordinates (p) of Earth surface feature can be written as:where [F] and [I] represent the transformation matrices from the sensor body-fixed coordinate system to image coordinate system. It’s worth noticing that the look vector of the sensor can be formed by the azimuth angle and elevation angle, which are comparable to the telescope on Earth. [S] is the transformation matrix between the sensor’s position in the Moon-based platform coordinate system and lunar topocentric coordinate system, [M] stands for the matrix transforming from the Moon-centred Moon-fixed coordinate system to lunar topocentric coordinate system, considering different positions on the lunar surface. Any positions of the Moon-based platform on the lunar surface can be referenced by the latitude and longitude, which are similar to the Earth. [L] and [C] are the relative matrices of the lunar orientation determination. For connecting the Earth coordinate systems and the lunar coordinate systems, an inertial reference system is used, i.e. the International Celestial Reference System (ICRS). The origin of the Geocentric Celestial Reference System (GCRS) is in the barycentre of the Earth while the Selenocentric Celestial Reference System (SCRS) shares the same orientation as GCRS and the origin is at the barycentre of the Moon. The transformation of the SCRS and the GCRS [T] shows up as the origin shift. The [P], [N], [R], [W], and [B] represent the matrices of the precession, nutation, rotation, polar motion and the bias separately. As for the time system, the Barycentric Dynamical Time (TDB) is adopted.