Difference between active and passive satellite

Satellites play a pivotal role in modern communication, navigation and data transmission systems. Active satellite amplifies and retransmits signals back to Earth using an onboard transponder. Passive satellite reflects signals back to Earth without any signal amplification or processing. Let us understand functions, working operation, examples, advantages, disadvantages and difference between these satellites.

Active Satellite

• The figure-1 depicts active satellite type.
• The active satellite has many benefits over passive satellite.
• It is equipped with transponders, amplifiers, transmitting and receiving antennas.
• It amplifies the signal received from earth station or ground station and retransmits the amplified signal back to earth.
• In addition to amplification, it performs frequency translation of the received signal before retransmission. Active satellite can generate power for its own operation.
• It is known as active repeater due to its functionality.

Examples

• Active Remote sensing satellites which transmit energy and analyze received energy to form the image.
• ACRIMSAT, Courier 1B
• Communication Satellites (e.g., Intelsat, Inmarsat): These satellites transmit telephone, television, and internet signals.
• Navigation Satellites (e.g., GPS Satellites): These satellites provide navigation and positioning services.
• Weather Satellites (e.g., GOES): These are used for meteorological observations.

Advantages of active satellite

Following are the benefits of active satellite.
1. Active satellites can amplify weak signals, making them suitable for long-distance communication.
2. They can cover vast areas and multiple regions due to their high altitude position.
3. Active satellites can manage multiple frequencies and provide multiple services simultaneously.
4. Some active satellites have onboard processing capabilities, allowing for better signal management and distribution.

Disadvantages of active satellite

Following are the drawbacks of active satellite.
1. They are more expensive to build, launch, and maintain due to the onboard electronics and power systems.
2. The lifespan is limited by the onboard fuel and battery, usually ranging from 10 to 15 years.
3. Requires complex technology and coordination, making it challenging to design and operate.

Passive Satellite

• The figure-2 depicts passive satellite type.
• The passive satellite is a reflector which receives the signal from the transmitting earth station and scatters the signal in all the directions.
• It works as large mirror and reflects the EM (Electro-Magnetic) radio waves without any modification and/or amplification.
• It does not have its own power source or electronic equipment unlike active satellite.
• Passive satellite can not generate power of its own and simply reflects the incident signal energy.
• It is known as passive repeater due to its functionality.

Examples

• Passive remote sensing satellites which collect the energy reflected or emitted from the surface.
• Starshine, PAGEOS
• Echo Satellites: Launched by NASA in the 1960s, these were large metalized balloons used to reflect microwave signals.
• Moon: The moon can also be considered a natural passive satellite as it reflects light from the Sun and radio signals from Earth.

Advantages of passive satellite

Following are the benefits of passive satellite.
1. Passive satellites are cheaper to build and launch as they do not require complex electronic systems.
2. They can last longer since there is no onboard electronic system that can degrade over time.
3. The design and operation are simpler, reducing maintenance costs.

Disadvantages of passive satellite

Following are the drawbacks of passive satellite.
1. Passive satellites cannot amplify signals, which can lead to weak or degraded signals over long distances.
2. They only reflect signals and cannot provide other services like broadcasting, navigation, or data transmission.
3. Due to lack of amplification, there can be higher signal loss and attenuation.

Difference Between Active and Passive Satellite

Following table compare active and passive satellite with respect to various aspects.

Conclusion

In summary, both active and passive satellites have unique characteristics and serve distinct purposes within the realm of satellite communication. Active satellites, with their advanced electronic components and signal amplification capabilities, are well suited for tasks requiring high quality signal transmission over vast distances. On the other hand, passive satellites are simpler and more cost effective, making them ideal for basic signal reflection purposes. By understanding difference between active and passive satellite, organizations and researchers can make informed decisions when choosing a satellite type for specific applications.

Satellite Related Posts

What is Difference between

RF and Wireless Terminologies