Geostationary Longitude Drift: Potential Well & Phase Portrait

Geostationary satellites are not truly fixed: Earth's slightly triaxial equatorial gravity field creates two stable "wells" and two unstable ridges around the GEO ring, and any satellite not parked exactly on a well slowly drifts, librating like a pendulum with a period of roughly two years. This 2D companion simulator drops the 3D terrain-and-orbit rendering entirely and instead shows the same governing equation through two native 2D representations: a potential-energy curve U(λ) with the satellite drawn as a ball rolling along it, and a phase-space plot of drift rate versus longitude that traces out the pendulum's libration orbits and separatrix. Station-keeping burns appear as instantaneous vertical jumps in the phase portrait — a signature that a 3D landscape view cannot show as directly. Live telemetry tracks longitude, drift rate, and the cumulative delta-V spent holding the slot, computed with the same tangential-impulse relation real mission planners use.