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introduction to orbit dynamics,and orbit classifications
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1
Orbit Dynamics
by
Eng\ A.Farrag
ADCS Team Leader
By Ahmad farrag
2
Overview
Kelper’s laws
Orbital elements
Orbit types
Reference co-ordinate system
Two body problem
By Ahmad farrag
3
Solar System
Are the positions of the planets and other solar system
objects random?
Do they obey certain laws?
What can these laws tell us about the history and
evolution of the solar system?
By Ahmad farrag
4
Kepler’s Laws
"The orbit of every planet is an ellipse
with the sun at a focus .“
"A line joining a planet and the sun
sweeps out equal areas during equal
intervals of time."
"The square of the orbital period of a
planet is directly proportional to the
cube of the semi-major axis of its orbit."
By Ahmad farrag
5
What is a satellite anyway?
A satellite is any object that orbits or
revolves around another object.
For example, the Moon is a satellite of
Earth, and Earth is a satellite of the Sun.
By Ahmad farrag
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Understanding Orbits
By Ahmad farrag
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Orbital “Keplerian” elements
The traditional orbital elements are the
six Keplerian elements
By Ahmad
farrag
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By Ahmad farrag
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Orbit types
Centric classifications– Galactocentric orbit: An orbit about the center of
a galaxy. Earth's sun follows this type of orbit.
– Heliocentric orbit: An orbit around the Sun. Inour Solar System, all planets, comets, and asteroidsare in such orbits.
– Geocentric orbit: An orbit around the planetEarth, such as the Moon or artificial satellites.
By Ahmad farrag
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By Ahmad farrag
Orbit types
Altitude classifications
– Low Earth Orbit (LEO): Geocentric orbits ranging in
altitude from 100–1000 km
– Medium Earth Orbit (MEO): Geocentric orbits ranging
in altitude from 1000 km to just below geosynchronous orbit
at 35786 km .
– High Earth Orbit (HEO): Geocentric orbits above the
altitude of geosynchronous orbit 35786 km.
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Orbit types
Inclination classifications
– Inclined orbit: An orbit whose inclination is not zero
degrees.
– Polar orbit: An orbit that passes above or nearly above
both poles of the planet on each revolution. Therefore it
has an inclination of 90 degrees.
By Ahmad farrag
15
Orbit types
Eccentricity classifications
– Circular orbit: An orbit that has an eccentricity of 0
and whose path traces a circle
– Elliptic orbit: An orbit with an eccentricity greater
than 0 and less than 1 whose orbit traces the path of
an ellipse .
• Molniya orbit: A highly elliptic orbit with inclination of
63.4° and orbital period of half of a sidereal day (roughly
12 hours). Such a satellite spends most of its time over a
designated area of the planet
By Ahmad farrag
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By Ahmad farrag
Orbit types
Synchronous classifications
– Sun-synchronous orbit: An orbit which combines altitude and inclination in such a way that the satellite passes over any given point of the earth surface at the same local solar time. Such an orbit can place a satellite in constant sunlight and is useful for imaging, spy, and weather satellites
– geosynchronous orbit is an orbit around the Earth with an orbital period matching the Earth's sidereal rotation period.
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Reference Co-ordinate System
Earth-Centered Inertial Frame (ECI)
or Inertial Co-ordinate System (ICS)
By Ahmad farrag
19
Reference Co-ordinate System
Earth-Centered Earth-Fixed Frame (ECEF) or
Greenwich Co-ordinates System (GCS)
By Ahmad farrag
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Reference Co-ordinate System
Orbital Co-ordinate System OCS
By Ahmad farrag
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Reference Co-ordinate System
Body Co-ordinate System BCS
By Ahmad farrag