Why in News:
- The SSLV was composed of three stages powered by solid fuels and these three performed their function as planned in the recent launch. However, when it came to the stage when the satellites had to be set in orbit, there was a glitch which resulted in the satellites being lost forever.
How did the failure happen?
- It was announced that there was a malfunctioning of a sensor which resulted in placing the satellites in an elliptical orbit, rather than a circular orbit.
- The ellipse or oval shape of the elliptical orbit is elongated in one direction and compressed in another (the so-called major and minor axes, which are like two radii of the ellipse).
- The shortest height above the Earth of this oval orbit was only about 76 km.
Why were the satellites lost?
- If the closest distance to the Earth is only 76 km, as it happened this time, there is an atmospheric drag experienced by the object at that height.
- Thereafter, unless adequate thrust is applied to overcome the drag, it will lose height and fall towards the Earth because of gravity and may eventually burn up due to friction.
What is the difference between circular and elliptical orbits?
- Mostly objects such as satellites and spacecrafts are put in elliptical orbits only temporarily. They are then either pushed up to circular orbits at a greater height or the acceleration is increased until the trajectory changes from an ellipse to a hyperbola and the spacecraft escapes the gravity of the Earth in order to move further into space — for example, to the Moon or Mars or further away.
- Satellites that orbit the Earth are mostly placed in circular orbits. One reason is that if the satellite is used for imaging the Earth, it is easier if it has a fixed distance from the Earth. If the distance keeps changing as in an elliptical orbit, keeping the cameras focussed can become complicated.