Orbital parameters: Orbital elements are the parameters, which are helpful for describing the orbital motion of satellites.

Following are the orbital parameters:

1. Semi major axis

2. Eccentricity

3. Mean anomaly

4. Argument of perigee

5. Inclination

6. Right ascension of ascending node

1. Semi major axis:

• The length of semi-major axis (a) defines the size of satellite’s orbit.
• It is half of the major axis.
• This runs from the center through a focus to the edge of the ellipse.
• So, it is the radius of an orbit at the orbit's two most distant points.

2. Eccentricity:

• The value of Eccentricity (e) fixes the shape of satellite’s orbit.
• This parameter indicates the deviation of the orbit’s shape from a perfect circle.
• If the lengths of semi major axis and semi minor axis of an elliptical orbit are a & b, then the mathematical expression for eccentricity (e) will be:

3. Mean anomaly:

• For a satellite, the point which is closest from the Earth is known as Perigee.
• Mean anomaly (M) gives the average value of the angular position of the satellite with reference to perigee.

4. Argument of perigee:

• Satellite orbit cuts the equatorial plane at two points. First point is called as descending node, where the satellite passes from the northern hemisphere to the southern hemisphere.
• Second point is called as ascending node, where the satellite passes from the southern hemisphere to the northern hemisphere.
• Argument of perigee (ω) is the angle between ascending node and perigee.
• Argument of perigee is measured in the orbital plane at earth’s center in the direction of satellite motion.

5. Inclination:

• The angle between orbital plane and earth’s equatorial plane is known as inclination (i).
• It is measured at the ascending node with direction being east to north.
• So, inclination defines the orientation of the orbit by considering the equator of earth as reference.
• There are four types of orbits based on the angle of inclination:
  1. Equatorial orbit
  2. Polar orbit
  3. Prograde orbit
  4. Retrograde orbit

6. Right ascension of ascending node:

• We know that ascending node is the point, where the satellite crosses the equatorial plane while going from the southern hemisphere to the northern hemisphere.
• Right Ascension of ascending node (Ω) is the angle between line of Aries and ascending node towards east direction in equatorial plane. Aries is also called as vernal and equinox.