[{"n": "Earth's orbit", "u": "/e/orbits-and-celestial-mechanics/earth-s-orbit/", "s": "Earth's elliptical orbit around the Sun defines the year and seasons."}, {"n": "Eclipse cycle", "u": "/e/orbits-and-celestial-mechanics/eclipse-cycle/", "s": "Intervals after which eclipses repeat under similar conditions."}, {"n": "Ecliptic", "u": "/e/orbits-and-celestial-mechanics/ecliptic/", "s": "Apparent path of the Sun on the celestial sphere."}, {"n": "Equatorial coordinate system", "u": "/e/orbits-and-celestial-mechanics/equatorial-coordinate-system/", "s": "A geocentric system for locating celestial objects."}, {"n": "Equinox", "u": "/e/orbits-and-celestial-mechanics/equinox/", "s": "Twice-yearly moment when day and night are nearly equal worldwide."}, {"n": "Equinox (celestial coordinates)", "u": "/e/orbits-and-celestial-mechanics/equinox-celestial-coordinates/", "s": "A direction in space, not a moment in time."}, {"n": "Escape velocity", "u": "/e/orbits-and-celestial-mechanics/escape-velocity/", "s": "Minimum speed to escape a body's gravitational pull."}, {"n": "Frozen orbit", "u": "/e/orbits-and-celestial-mechanics/frozen-orbit/", "s": "An orbit minimizing perturbations for long-term stability."}, {"n": "Geostationary orbit", "u": "/e/orbits-and-celestial-mechanics/geostationary-orbit/", "s": "A fixed point in the sky for global communications and observation."}, {"n": "Geosynchronous orbit", "u": "/e/orbits-and-celestial-mechanics/geosynchronous-orbit/", "s": "An Earth orbit synchronized with the planet's rotation."}, {"n": "Graveyard orbit", "u": "/e/orbits-and-celestial-mechanics/graveyard-orbit/", "s": "A disposal orbit for end-of-life satellites to reduce debris."}, {"n": "Halo orbit", "u": "/e/orbits-and-celestial-mechanics/halo-orbit/", "s": "Periodic, non-planar orbit around Lagrange points."}, {"n": "Hohmann transfer orbit", "u": "/e/orbits-and-celestial-mechanics/hohmann-transfer-orbit/", "s": "An orbital maneuver using two burns to transfer between orbits."}, {"n": "Horseshoe orbit", "u": "/e/orbits-and-celestial-mechanics/horseshoe-orbit/", "s": "A co-orbital motion tracing a horseshoe shape relative to a larger body."}, {"n": "Libration", "u": "/e/orbits-and-celestial-mechanics/libration/", "s": "Cyclic variation in Moon's apparent position revealing extra lunar surface."}, {"n": "Lissajous orbit", "u": "/e/orbits-and-celestial-mechanics/lissajous-orbit/", "s": "Quasi-periodic orbit around Lagrangian points used by spacecraft."}, {"n": "Molniya orbit", "u": "/e/orbits-and-celestial-mechanics/molniya-orbit/", "s": "A high-latitude satellite orbit with long dwell time over the north."}, {"n": "Orbit of the Moon", "u": "/e/orbits-and-celestial-mechanics/orbit-of-the-moon/", "s": "The Moon's orbit is a stable, complex path studied by lunar theory."}, {"n": "Orbital eccentricity", "u": "/e/orbits-and-celestial-mechanics/orbital-eccentricity/", "s": "Parameter measuring deviation of an orbit from a perfect circle."}, {"n": "Orbital elements", "u": "/e/orbits-and-celestial-mechanics/orbital-elements/", "s": "Parameters that uniquely identify a specific orbit."}, {"n": "Orbital inclination", "u": "/e/orbits-and-celestial-mechanics/orbital-inclination/", "s": "Angle measuring tilt of an orbit relative to a reference plane."}, {"n": "Orbital period", "u": "/e/orbits-and-celestial-mechanics/orbital-period/", "s": "Time for one full orbit around a primary body."}, {"n": "Orbital resonance", "u": "/e/orbits-and-celestial-mechanics/orbital-resonance/", "s": "Orbital resonance shapes planetary systems through periodic gravitational interactions."}, {"n": "Orbital station-keeping", "u": "/e/orbits-and-celestial-mechanics/orbital-station-keeping/", "s": "Keeping spacecraft in orbit through precise thruster maneuvers."}, {"n": "Polar orbit", "u": "/e/orbits-and-celestial-mechanics/polar-orbit/", "s": "Satellite orbit passing near both poles each revolution."}]