What are space probes?
Space probes are spacecraft sent on missions to study various bodies in the Solar System and even beyond.
What are equatorial and polar orbits of satellites?
An orbit on or near the plane of the Equator is called an equatorial orbit. An orbit on or near the plane of the poles is called a polar orbit.
What is retrograde orbit of a satellite?
In a direct orbit, the satellite goes eastwards as it crosses the Equator from the southern to be northern hemisphere. In a retrograde orbit the motion gets reversed.
What is the optimum condition for a satellite launch?
A satellite is generally launched towards the east possibly from a point on the Equator, if launching facilities are available there.
What is regression of the nodes in the orbit of a satellite?
A satellite cannot go round the Earth at a fixed altitude closer to Earth, as the Earth is not a perfect sphere. The orbit of a satellite is determined by the shape of the Earth which has an educational bulge. The earth is also slightly pear-shaped. All these variations produce gravitational anomalies that affect the shape of the orbit.
As a satellite crosses the equatorial region, the plane of its orbit will change or shift because of the Earth’s equatorial bulge. This is known as regression of the nodes. When a satellite passes from the southern to the northern hemisphere, in a west to east direction, the satellite will have a westward regression. If the satellite passes from east to west, from the southern to the northern hemisphere, it will have an eastward regression. The rate at which the regression takes place depends on the altitude of the orbit and its inclination to the Equator. No regression takes place in a true polar orbit or in a true equatorial orbit.