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Words begining with "K"
KSC (Kennedy Space Center)
See NASA Centers.
Keplerian elements (aka Satellite Orbital Elements)
The set of six independent constants which define an orbit - named
for Johannes Kepler [1571-1630]. The constants define the
shape of an ellipse or hyperbola, orient it around its central body,
and define the position of a satellite on the orbit. The classical
orbital elements are:
- a: semi-major axis, gives the size of the orbit
- e: eccentricity, gives
the shape of the orbit
- i: inclination angle, gives the angle of the orbit plane to
the central body's equator
- (Uppercase Omega): right ascension of the ascending node,
which gives the rotation of the orbit plane from reference
axis
- (Lowercase Omega): argument of perigee is the angle from the
ascending nodes to perigee point, measured along the orbit in the
direction of the satellites motion
- (Uppercase Theta): true anomaly gives the location of the
satellite on the orbit.
Kepler's Three Laws of Motion
Any spacecraft launched into orbit obeys the same laws that govern
the motions of the planets around our sun, and the moon around the
Earth. Johannes Kepler formulated three laws that describe these
motions:
- Each planet revolves around the sun in an orbit that is an
ellipse with the sun as its focus or primary body. Kepler
postulated the lack of circular orbits - only elliptical ones
-determined by gravitational perturbations and other factors.
Gravitational pulls, according to Newton, extend to infinity,
although their forces weaken with distance and eventually become
impossible to detect. (See
Newtons law of universal gravitation) Spacecraft orbiting the
Earth are primarily influenced by the Earth's gravity and
anomalies in its composition, but they also are influenced by the
moon and sun and possibly other planets.
- The radius vector - such as the line from the center of the
sun to the center of a planet, from the center of Earth to the
center of the moon, or from the center of Earth to the center of
gravity of a satellite - sweeps out equal areas in equal periods
of time.
- The square of a planet's orbital period is equal to the cube
of its mean distance from the sun times a constant. As extended
and generalized, this means that a satellite's orbital period
increases with its mean distance from the planet. See Newtons law
of universal qravitation and laws
of motion.
kilohertz (kHz)
One thousand hertz, i.e., one
thousand cycles per second.
Kilometer (km)
Metric unit of distance equal to 3,280.8 feet or 0.621 statute miles.
Knot
Unit of speed of one nautical mile (6,076.1 feet) an hour.
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Responsible NASA Official:
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