Satellite Communication: Working, Services, and Complete Explanation

What is a Satellite?

A satellite is an object in space that orbits or revolves around a larger object. Satellites may be natural (such as the Moon orbiting the Earth) or artificial (such as the International Space Station).

An artificial satellite is a man-made object launched into orbit using a rocket. More than 3,000 artificial satellites currently orbit the Earth. Their size, structure, and height depend on their specific purpose.

Satellite sizes vary widely. Some CubeSats measure only 10 cm, while some communication satellites have solar panels extending more than 50 meters. The International Space Station (ISS) is the largest man-made satellite. Its core module is as large as a five-bedroom house, and with solar panels, it expands to the size of a rugby field.

Today, satellites are used for global communication, navigation, monitoring, surveying, data collection, weather forecasting, and many other applications.

What is Satellite Communication?

Satellite communication refers to the use of artificial satellites to establish communication links between different locations on Earth. It plays a vital role in the global telecommunications system. Approximately 2,000 satellites relay analog and digital signals—voice, video, and data—around the world.

The first artificial satellite, Sputnik 1, was launched by the Soviet Union on October 4, 1957. It had a diameter of 58 cm and four antennas that transmitted low-frequency radio signals. It orbited Earth every 96.2 minutes. Although it functioned for only 22 days and remained in orbit for three months, its launch initiated the space race.

Ground wave and sky wave propagation have a maximum hop distance of about 1500 km. Satellite communication overcomes this limitation, enabling transmission far beyond the line-of-sight range. Since satellites are placed high above Earth, communication becomes easier between any two Earth stations, bypassing Earth’s curvature.

Working of Satellite Communication

Communication satellites act like space mirrors that reflect radio, television, and internet signals from one region to another. The working involves three main stages:

1. Uplink

The television or communication signal is first sent from an Earth station to the satellite. This upward transmission is called the uplink.

2. Transponders

The received signal is processed by transponders—radio receivers, amplifiers, and transmitters. Transponders amplify the signal and change its frequency without altering the information being transmitted. Different satellites use different transponder configurations.

3. Downlink

Finally, the processed signal is transmitted back to another Earth station. This path from the satellite to Earth is called the downlink. Generally, a single uplink may serve multiple downlinks.

Services Provided by Satellite Communication

Satellite communication services are broadly classified into two types:

1. One-Way Satellite Communication

This type of communication occurs when the signal travels in only one direction—from a transmitting Earth station to a receiving Earth station via a satellite.

Common examples include:

• Radio broadcasting and position-location services
• Space tracking operations
• Broadcast satellites used for internet and TV services

2. Two-Way Satellite Communication

In two-way communication, information is exchanged between two Earth stations. This provides point-to-point connectivity.

The signal travels from the first Earth station to the satellite and then to the second Earth station, and vice versa—resulting in two uplinks and two downlinks.