List of Terms and Concepts
- Altitude
- as used here, the height of an object above the average surface of the Earth's oceans.
- Analemma
- a term in astronomy used to describe the plot of the positions of the Sun on the celestial sphere throughout one year. Closely resembles a figure-eight.
- Apogee
- is the farthest point that a satellite or celestial body can go from Earth, at which the orbital velocity will be at its minimum.
- Eccentricity
- a measure of how much an orbit deviates from a perfect circle. Eccentricity is strictly defined for all circular and elliptical orbits, and parabolic and hyperbolic trajectories.
- Equatorial plane
- as used here, an imaginary plane extending from the equator on the Earth to the celestial sphere.
- Escape velocity
- as used here, the minimum velocity an object without propulsion needs to have to move away indefinitely from the Earth. An object at this velocity will enter a parabolic trajectory; above this velocity it will enter a hyperbolic trajectory.
- Impulse
- the integral of a force over the time during which it acts. Measured in (N·sec or lb * sec).
- Inclination
- the angle between a reference plane and another plane or axis. In the sense discussed here the reference plane is the Earth's equatorial plane.
- Orbital characteristics
- the six parameters of the Keplerian elements needed to specify that orbit uniquely.
- Orbital period
- as defined here, time it takes a satellite to make one full orbit about the Earth.
- Perigee
- is the nearest approach point of a satellite or celestial body from Earth, at which the orbital velocity will be at its maximum.
- Sidereal day
- the time it takes for a celestial object to rotate 360°. For the Earth this is: 23 hours, 56 minutes, 4.091 seconds.
- Solar time
- as used here, the local time as measured by a sundial.
- Velocity
- an object's speed in a particular direction. Since velocity is defined as a vector, both speed and direction are required to define it.
Read more about this topic: Geocentric Orbit
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