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  • Mayur Pawar

Do you know: How do scientist locate the position of the satellite in orbit?

In school, we learn the determination of object in the 2-dimensional plane. In that, we have two variables to determine the position (Length and breath) of the object in the plane. As we go further studies, we get to know about 3rd dimension i.e. height. I might though. as satellites in the 3-dimensional plane then we can easily determine or define the position of it. But that's definitely not the case, to define the position of the satellite ultimately the orbit of the satellite. we need six parameters excluding time.


1. Eccentricity: The parameter determining the shape of the orbit is known as the eccentricity. It is a property of the conic section that ranges from a circle to a hyperbola. For a circle the eccentricity equals zero, for an ellipse it is less than one, for a parabola it is equal to one and finally for a hyperbola, it is greater than one. Eccentricity: The parameter determining the shape of the orbit is known as the eccentricity. It is a property of the conic section that ranges from a circle to a hyperbola. For a circle the eccentricity equals zero, for an ellipse it is less than one, for a parabola it is equal to one and finally for a hyperbola, it is greater than one.


2. Semi-major axis: Depending upon the conic the semi-major axis is defined as the half of the sum of periapsis and apoapsis distance for eccentricity less than one.


3. True/Mean Anomaly: The quantity describing the time since the perigee passage is known as the true anomaly and it is denoted by. The true anomaly ranges from 0 to 2. However, the better representation could be in terms of the mean anomaly as it is always referenced to some epoch to correctly illustrate the position of the orbiting body.


4. Inclination: The angle between the orbital plane of the orbiting body (small) and the bigger central body is known as the inclination of the small body. The inclination is measured locally and is relevant according to the reference body. For e.g. the plane of rotation of the Earth around the Sun is known as the ecliptic however the inclination of a satellite is measured according to the Earth while taking into consideration of the equatorial plane and not the ecliptic so it like all the other Keplerian elements is a localized quantity with only the immediate central body in consideration. The convention of representing the inclination of an orbit is with an italicized i and the inclination is measured from the line of nodes i.e. the line where the orbital and the equatorial planes cross over. The inclination of an orbit ranges from 0 to pi.


5. Right Ascension of the Ascending node (RAAN): The angle between the vernal equinox and the point on the orbit at which the orbiting body crosses the equator from the South to the North is known as the right ascension of the ascending node. The RAAN is represented as Ω and it ranges from 0 to 2. 6. The argument of perigee: The angle between the direction of the ascending node i.e. when the orbiting body crosses from the South to the North and the direction of the perigee is known as the argument of perigee and it is represented as The argument of perigee ranges from 0 to pi.


6. Argument of perigee: The angle between the direction of the ascending node i.e. when the orbiting body crosses from the South to the North and the direction of the perigee is known as the argument of perigee and it is represented as The argument of perigee ranges from 0 to pi.


Figure illustrating the Orbital Parameters