Rajasthan Board RBSE Class 8 Science Notes Chapter 12 Artificial Satellite
We know that eight planets – Mercury, Venus, Earth, Mars, saturn, jupiter, Uranus (arun) and Neptune (varun) move around the Sun. Around them some celestial bodies are moving called satellites. They are all the part of our universe and solar system. These all satellites are natural satellites like- moon is the natural satellite of our earth.
Man made satellites which are moving around other planets are called artificial satellites and are different from natural satellites. These satellites have made firm and regular communication from satellites to earth, we are able to use television, radio, mobile etc.
Launching of Artificial Satellites:
If we throw things like – ball, stone, rubber, duster etc. one by one they all come down towards the earth. These observations prove that due to attraction of earth all things come down. This effect is called gravitational force. If we throw things upward with different speed or force they cover different distances. Bullet fired by a gun or rocket of explosives or crackers have different velocities.
In the same way if a very high velocity rocket supplies such a velocity to celestial body that it crosses the gravitational force, then it wouldn’t come back to earth hence that minimum velocity by which any thing could be launched in universe by crossing the limit of gravitational force is called escape velocity of earth. Any thing has escape velocity of 11.2 km/sec. Hence if any thing is send upward more than escape velocity i.e. more than 11.2 km/sec then it would not only cross the gravitational force but it would move in a definite path around the earth and wouldn’t come back on earth. It is called artificial satellite. It is launched with the help of rocket or satellite launching craft.
Types of Artificial Satellites:
On the basis of relative distance between satellite and earth and its uses man-made satellites are of two types:
1. Geo stationary Satellite
2. Polar Satellite
- Geo Stationary Satellite: Every satellite moves around the earth in its fixed path called orbit. Any satellite which is moving around the earth but when see from the earth it looks stationary is called Geo Stationary Satellite. This satellite is located at approx. 36000 km. height from the earth’s surface. These satellites move in equatorial orbit. The revolutional period of Geostationary satellite is equal to the rotational period of earth i.e., 24 hours, it also as its own direction of movement like earth i.e., west to east it completes its one revolution around the earth in 24 hours in its own orbit. Hence it looks stationary when seen from the earth.It is used in satellite, telephone, television, radio and in other global communication. So, it is also called communication satellite.
- Polar Satellite: Those satellites which move in Polar orbit on earth are called Polar Satellites. They have distance from earth’s surface 500-800 kms. They give information about atmosphere like – Ozone layer, pictures of clouds etc. Informations given by Polar satellites are remote sensing and important to study weather and environment. The important is that polar satellites can observe whole earth with the help of their cameras twice in a day. Remote sensing getting information about any thing or substance without coming in contact of it is called remote sensing. India has launched many Remote sensing satellites like – IRS – IA, IRS-2B, IRS-3C etc. micro waves and radio waves can travel in vacuum i.e. without medium.
Uses of Artificial Satellites:
- In telephone, mobile, television, internet etc. It receives waves from the instruments located on earth at any place and can send them at different places on earth.
- It helps in getting information about weather and under earth.
- Evaluation area of crops and production.
- Alertness about drought and flood and to know about harms of them.
- Discovery of underground water and management of water resources.
- Discovery of minerals under earth.
- Helping in environment conservation.
- Security of airports, seaports, military stations.
- Spy of military activities.
- To get information regarding universe and atmosphere.
- To get right location of aeroplane, ship, person or place.
India’s main Artificial Satellites:
The first satellite was sent by Russia on 4 October, 1957. To-day more than 3000 artificial satellites are working. India sent its first satellite in 1975 till now about more than 70 satellites are sent in the universe. These are launched with the help of different space shuttles. Most of them are sent with the help of American, Russian and European space shuttles.
Satellites launched by India through Indian Space and Research Organization are:
- India’s first Artificial satellites name is Aryabhatta. It Is named after famous ancient Indian astrologer and mathematician, Aryabhatta. It was launched on 19th April, 1975 from Space Centre of Russia, Baikanour. It’s main function was study of India’s atmosphere.
- Bhaskar-1 It is India’s first remote sensored satellite, launched in 1979.
- From 1980 India started launching polar satellites. These are considered India’s remote sensing or IRS series satellites. These satellites are useful in managing natural resources, weather forecast and universe.
- In 1980 INSAT series satellites were launched with the help of Europian space shuttle. They are used in field of communication and weather forecasting.
- Satellite launched for weather information is named after first Indian woman astronaut Kalpana Chawla on 5th February, 2003. It is India’s first weather related satellite.
- In 2004 INSAT and EDUSAT is first Indian satellite which is meant for education only.
- Indian Space Research Organization : In the leadership of Homi Jahangir Bhabha, Atomic Energy Department organized Indian National Committee for Space Research (INCOSPAR) in 1962.
Indian Space and Research Organization:
In 1969 (ISRO) it was reorganised as Indian Space and Research Organization. In India manufacturing, development and launching of artificial satellites are done by ISRO. The contribution of launching of space programme in India goes to Dr. Vikram Ambalal Sarabhgi, with the help of ISRO based space application programmes, space and satellites related programmes, are developing. India’s famous scientist Dr. A.P.J. Abdul Kalam had played an important role in Indian Satellites launching programmes. To-day India has become independent in making artificial satellites even America and other nations are utilising Indian Space Rockets in launching their satellites.
Centre of ISRO are located in all over India. Its main centre is at Shri Harikota (SHAR) Chennai and for research National Centre Physical Research Lab. (PRL) at Ahmedabad and in Thiruvananthapuram, Vikram Sarabhai Space Centre. In Jodhpur city of Rajasthan Remote Sensing Centre is located for getting pictures sent by satellites to study informations and datas.