1} Apogee, Perigee
- 2} ascending node and descending node -
3} Argument of Perigee
- 4} Right ascension of ascending node
- 5} mean anamoly & eccentric anamoly -

Marks: 10 M

Year: May 2012

• Apogee: A farthest point from the Earth’s surface in an orbit is known as Apogee.
• Perigee: A nearest point from the Earth’s surface in an orbit is known as Perigee.
• Ascending node: The point at which satellite intersects the equatorial plane while going from south to north.
• Descending node: The point at which satellite intersects the equatorial plane going from north to south.
• Right Ascension of the ascending node (Ω): It is the angle measured eastward in the equatorial plane from the line of aries to the ascending node. Thus, Ω is the longitude of the ascending node.
• Argument of Perigee (ω): The angle from the ascending node to the Perigee measured in the orbital plane at the earth’s center in the direction of motion.

• Eccentric Anomaly (E): It is the central angle measured from X-axis to the vertical projection of a satellite over the circle of radius a. It is given as:

$cosE=\frac{e+cos v}{1+ecosv}$

$where, e – eccentricity$

$v - True anomaly$

• Mean Anomaly (M): It may be considered as True Anomaly if the satellite would have proceeded along a circular orbit of the same period T as that of the elliptical orbit. Mean anomaly gives average value of the angular position of the satellite with reference to Perigee.

$M=E-esinE$

$where, E – Eccentric anomaly$

$e - eccentricity$