Geometry and coordinate conventions. The sky-plane coordinates X ≡ (X, Y)^T are centered on the star, while x ≡ (x, y)^T are centered on the planet. The origins are denoted by O_s (stellar center) and O_p (planet center), respectively, with O_p located at ﹩\left({X}_{p}(t),{Y}_{p}(t)\right)﹩ in the (X, Y) frame. The large open circle represents the projected stellar disk, and the black filled circle represents the projected planetary silhouette. The dashed line indicates the projected planetary trajectory, and the arrow indicates the direction of motion.