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The point in the orbit of the moon or a satellite at which it is furthest from the Earth. For orbits around bodies other than Earth, the term 'apoapsis' is used. The significance is that at apogee, the satellite has the least amount of kinetic energy and moves the slowest.

A maneuver in which a spacecraft gains speed and alters its trajectory by passing close to a planet. This can significantly save fuel, extend the lifetime of missions, and enable visits to more distant bodies in the solar system.

Three laws describing the motion of planets around the sun, which are also applicable to satellite orbits: 1) Orbits are elliptical, with the central body at one focus. 2) A line segment connecting a planet to the sun sweeps out equal areas during equal intervals of time. 3) The square of the orbital period is proportional to the cube of the semi-major axis of its orbit.

A measure of the deviation of an orbit from a perfect circle, ranging from 0 to 1, where 0 is a circle and values closer to 1 indicate more elongated orbits. Eccentricity affects the satellite's speed and the variability of its distance from Earth over its orbit.

A nearly polar orbit that allows a satellite to pass over the same part of the Earth at roughly the same local solar time each day. This is particularly useful for satellites that perform Earth-observation, as it ensures consistent lighting conditions for the sensors.

The point in the orbit of the moon or a satellite at which it is closest to the Earth. For orbits around bodies other than Earth, the term 'periapsis' is used. Satellites speed up as they reach perigee due to increased gravitational pull.

The longest diameter of an elliptical orbit, which is half the length of the major axis. The semi-major axis is significant in that it determines the size of the orbit and, through Kepler's third law, the orbital period of the satellite.

The tilt of an object's orbital plane in relation to the equatorial plane of the central body, often expressed in degrees. It is significant in determining the type of orbit (e.g., equatorial, polar) and can affect the coverage and communication abilities of a satellite.

An orbit relatively close to Earth's surface, typically between 160 to 2,000 kilometers in altitude. LEO is used for many types of satellites, including those for imaging, weather, and communication, due to its proximity to the Earth which allows for lower latency and higher resolution images.

A measure of the change in velocity required for a spacecraft to perform a maneuver. It is a key concept in orbital mechanics when planning missions, as the total ∆V budget dictates the spacecraft's capability in changing orbits, performing landings, avoiding collisions, etc.

A circular orbit directly above the Earth's equator at approximately 35,786 kilometers where the satellite's orbital period matches the Earth's rotation period. This creates the effect of the satellite being stationary relative to the Earth's surface, which is useful for communication and weather satellites.