Satellite: The celestial body revolving around a planet is called its satellite. There are two types of satellites –
- natural satellites,
- artificial satellites.
For example, the moon is the natural satellite of the earth, and Aryabhatta, Rohini, Apple, etc. are the artificial satellites of the earth.
The entire area of the Earth cannot be covered by the sky-wave transmission method, because it is not possible to have continuous repeater due to the odd geographical conditions (eg, many oceans in the middle). Therefore, it is necessary that communication is high. Be on frequency. Waves of frequency greater than 30 MHz cannot be transmitted by conventional methods. Communication satellites are used for this. Satellites use microwaves in communication.
A communication satellite is a satellite that revolves around the Earth in a circular orbit from the west to the festival in such a way that its period of time is kept equal to the rotation period of the Earth’s own axis. Therefore, this satellite always seems to be stable with respect to the Earth. Thus these communication satellites are used for the transmission of long distances. They are also called Bhasthair satellites or synchronous satellites.
Such communication satellites have the necessary equipment (radio transponders) for the capture and transmission of microwave signals. Micro-wave signals of one frequency (uplink) are transmitted from the chalk ball station to the satellite. These signals are modified and amplified by eclipsing the equipment on the satellite, after which they are further transmitted to the receiver station on earth on another downlink. Both the frequencies of the uplink and downlink fall in the microwave or UHF region. Such high-frequency waves cross the ionosphere.
Therefore, the transmitter and receiver antennas are placed on the earth at fixed tilt angles. The frequency range of the satellite communication system is 1 GHz to 10 GHz. The feature of this communication system is that satellite communication allocates long distances without any disturbance. These long distances are easy and wasteful means of communication for remote hill areas. It is a suitable communication medium for television, telephone, and mobile phone services. This communication medium is not suitable in terms of privacy.
The technique that is used to observe distant objects and study their properties is called remote sensing. The remote sensing device gets complete information about distant objects without coming into contact with them. Remote sensing is concerned with the measurement of energy that is emitted, transmitted, or altered by a distant object to determine some of its physical properties (eg, location, shape, color, nature, and heat, etc.). Nowadays, remote sensing is being used commonly for obtaining information with the help of electromagnetic technology.
Such remote sensing devices are called active remote sensing devices when electromagnetic energy is used to illuminate the object to be observed in a remote sensing device like Rodar. When illumination is not generated by the device (such as viewing the Earth with a camera in sunlight) it is called passive remote sensing.
Thus in an active remote sensing device, the device itself sends microwave energy to the surface of the Earth in the form of pulses and transmits the reflected signal. The passive remote sensing device mainly relies on the sun on as a source of electromagnetic energy. This technique covers the spectrum of the gamma-ray field from the low-frequency radio wave, that is, the entire electromagnetic spectrum. Nowadays the technique of remote sensing has been advanced from space depends on the research of Earth and planets to a sufficient extent.
The remote sensing satellite should rotate around the Earth near the polar sensing satellite located at 918 km (Altitude) so that it passes through the given area at the same time. The orbit of such a satellite is called (sun sinconus) orbit. The remote sensing satellite repeatedly photographs it while passing through a particular area so that it can be comparatively studied.
IRS, -IA; IRS-IB, and IRS-IC are Indian remote sensing satellites.
Applications of remote sensing-
- It is used in taking photographs of wasted land.
- It is used in studying the area of the earth surrounded by forests, types of plants, and the density of the forest in a particular area.
- It is used to search for debris of a crashed aircraft or jetplane.
- It is used for water survey on earth.
- It is used to identify the source of pollution.
- It is used to assess flood damage.
- It is used to locate the place inside the ground where a nuclear explosion has taken place.
- the airspace.