Types of Satellites UPSC

 Types of Satellites

1. Communication Satellite

Communications satellites are used for television, telephone, radio, internet, and military applications. 

These satellites use a wide range of radio and microwave frequencies.

The orbits where these satellites are located are geosynchronous orbits, Molniya orbits and LEO.

The two main components of a communications satellite are 

○ The satellite bus and 

○ The communications payload.

Bus contains the support vehicle and control subsystems like thermal control, solar panels to provide energy etc.

Communications payload contain the parts that carry out the business of the satellite e.g. transponders that receive signals in the form of uplink frequency from Earth, amplifies the signals and downlinks the frequency and transmits it to Earth.

2. Earth Observation Satellite

These satellites usually are in sun synchronous orbit and chiefly serve the non-military purposes.

Earth observation satellites are used for studying weather, for monitoring the environment, atmospheric trace gas content, sea state, ocean color, and ice field etc., predicting disasters.

Remote sensing is a chief feature of these satellites. 

It refers to observing the Earth’s surface and objects from a distance and collecting the data which can be used for many applications.

Some examples of remote sensing are such as

○ Assessment of change in shorelines, 

○ Monitoring ocean currents, 

○ Tracking sea ice, 

○ Tracking natural disasters like flooding, hurricanes etc. and 

○ Managing natural resources and assessing the changes in them e.g. observing the change in Earth’s vegetation.

3. Navigation Satellite

A) GPS - Global Positioning System:

• It is owned by the US government and controlled by the US Air Force.
• GPS is used for both civilian and military purposes.
• The satellite constellation consists of 24 satellites and provides global coverage.
• Segments of GPS are:

○ The satellite constellation- the satellites are located in MEO and provide ranging signals and navigation data.

○ Ground control network- tracks and maintains the satellite constellation by 

tracking satellite health.

○ User equipment- Determines user position, velocity and time (PVT) by computing the received signals from the satellite constellation.

B) Galileo:

Galileo is Europe’s own global navigation satellite system, under civilian control.

It is interoperable with GPS and Glonass.

The fully deployed Galileo system will consist of 24 operational satellites plus six in-orbit spares, positioned in three circular Medium Earth Orbit (MEO) planes at 23,222 km altitude above the Earth.

C) GLONASS:

It is Russia’s GNSS that consists of 24 satellites and 3 spares.

Second only to GPS, it provides global coverage.

The satellites are located in MEO at 19,100 kilometres above Earth. 

D) China’s BeiDou:

It is a GNSS that consists of two separate satellite constellations- one is a test system called BeiDou-1 that was operational regionally while the other 

one called BeiDou-2 is meant to provide full global coverage and is being developed.

BeiDou -2 is the second generation GNSS of China and is deemed to be fully operational from 2020.