CMD of an example mock satellite galaxy located at a distance of 98.95 kpc, with a half-light radius of 69.45 pc and an absolute magnitude M_V = −6.38 (Chain B). The red points represent point sources selected from the central region of the mock satellite up to 2 times the satellite’s r_h. These point sources consist of both the mock satellite’s member stars and the Milky Way foreground stars. The yellow region corresponds to the selection criteria derived from Eq. (7) to isolate the member stars of the satellite. Stars falling within this region are considered as member stars of the mock satellite.