Structural layout of the GECAM payload shown from different perspectives and comprising 25 GRDs (designated G01 through G25) and eight CPDs (designated C01 through C08). The payload comprises two main components: the detector dome housing and the EBOX. The payload coordinate system is defined such that the +X, +Y, and +Z axes align with the central normals of detectors G18, G24, and G01, respectively (Zhao et al. 2023c).