Co-orbital satellite

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Co-orbital satellites are satellites that share the same mean orbit. Some trade orbits when the satellite closest to the planet or star catches up with the outer one. Saturn's moons Janus and Epimetheus are this type. More commonly, the satellites are positioned at the planet's L4 or L5 Lagrange points with respect to the Sun. Lagrange points are five positions in space where a small object with no other forces acting on it can be stationary with respect to two larger objects. Earth has two co-orbital satellites of this type, asteroids 2002 AA₂₉ and 3753 Cruithne.