orbital
parameters:
Apogee:
A point for a satellite farthest from the Earth. It is denoted as ha.
Perigee:
A
point for a satellite closest from the Earth. It is denoted as hp.
Line
of Apsides: Line joining perigee and apogee through
centre of the Earth.
It
is the major axis of the orbit. One-half of this line‟s length is the
semi-major axis equivalents to satellite‟s mean distance from the Earth.
Ascending
Node: The point where the orbit crosses the equatorial
plane going from north to south.
Descending
Node: The point where the orbit crosses the equatorial
plane going from south to north.
Inclination:
the
angle between the orbital plane and the Earth‟s equatorial plane. Its measured
at the ascending node from the equator to the orbit, going from East to North.
Also, this angle is commonly denoted as i.
Line
of Nodes: the line joining the ascending and
descending nodes through the centre of Earth.
Prograde
Orbit: an orbit in which satellite moves in the same
direction as the Earth‟s rotation. Its inclination is always between 00
to 900. Many satellites follow this path as Earth‟s velocity makes it
easier to lunch these satellites.
Retrograde
Orbit: an orbit in which satellite moves in the same
direction counter to the Earth‟s rotation.
Argument
of Perigee: An angle from the point of perigee
measure in the orbital plane at the Earth‟s centre, in the direction of the
satellite motion.
Right
ascension of ascending node: The definition of an
orbit in space, the position of ascending node is specified. But as the Earth
spins, the longitude of ascending node changes and cannot be used for
reference. Thus for practical determination of an orbit, the longitude and time
of crossing the ascending node is used.For absolute measurement, a fixed
reference point in space is required.
It could also be defined as “right
ascension of the ascending node; right ascension is the angular position
measured eastward along the celestial equator from the vernal equinox vector to
the hour circle of the object”.
Mean
anamoly: It gives the average value to the
angular position of the satellite with reference to the perigee.
True anamoly: It is the angle from point of perigee to the satellite‟s position, measure at the Earth‟s centre.
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