Types of Satellites and their applications

Communications Satellite

Communications satellites, typically located in geostationary orbit (GEO) and low Earth orbit (LEO), are equipped with transponders (a combination of radio signal receivers and transmitters) that receive signals from Earth and send them back to Earth. This capability enables communications links between areas that were previously isolated due to distance or other barriers. These communications satellites support a variety of media transmissions, including radio, television, telephone, and Internet services.

Communications satellite orbit

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Communication satellites are mostly placed in GEO or LEO orbits depending on their functions.

Geostationary Orbit (GEO): Communication satellites are typically located in geostationary orbit (GEO), approximately 35,786 km above the Earth’s surface. This orbit is ideal for telecommunications and broadcasting because it has minimal interference and a stable position relative to the Earth. GEO satellites offer several advantages, including wide coverage, stable bandwidth, and efficient use of electricity. For example, the Indian Space Research Organization’s GSAT series operates in GEO orbit and provides various telecommunication services such as broadcasting and Internet connectivity. However, a significant disadvantage of GEO satellites is their high latency, which affects real-time communications.

Low Earth Orbit (LEO): Satellites in low Earth orbit are 160 to 1,000 kilometers above the Earth’s surface and have lower latency and higher bandwidth, which helps speed up data transmission. This makes LEO a top choice for deploying satellite constellations for high-speed Internet services. For example, SpaceX’s Starlink project uses a constellation of more than 4,200 satellites located approximately 550 kilometers in LEO to provide high-speed Internet worldwide.

Applications of communication satellites

Indian National Satellite (INSAT) System: The INSAT system is one of the largest communication satellite networks in the Asia-Pacific region. It supports various communication and broadcasting services across India.

Meteorology: Satellites equipped with C-band, Extended C-band and Ku-band transponders play a vital role in meteorology. They provide essential services including weather forecasting, disaster warning and search and rescue operations.

High-Speed ​​Internet Service: Modern communication satellites now provide high-speed Internet service, providing fast and reliable connections for a variety of applications.

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Earth Observation Satellite

Earth observation satellites are essential for monitoring the Earth from space, providing valuable data on environmental changes, and aiding rapid response in emergency situations such as natural disasters and conflicts. These satellites enable consistent and repeatable monitoring of the Earth’s surface and atmosphere. Examples of different Earth observation satellites include ISRO’s CARTOSAT series, OCEANSAT, EOS-04, ESA’s EUMETSTAT, etc.

Earth observation satellites are classified into the following types:

Weather Satellites: These satellites are used to track and forecast weather patterns. They are primarily located in geostationary orbit (GEO) and provide a continuous view of the Earth, allowing scientists to monitor cloud formation, track weather systems, and predict changes with high accuracy.

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Remote Sensing Satellites: These satellites help detect and monitor the physical characteristics of an area by measuring reflected and emitted radiation from a distance. Remote sensing satellites orbit the Earth in different paths depending on their specific function – polar, non-polar low earth orbit (LEO) or GEO. Geographic Information System (GIS) satellites are a subset of remote sensing satellites, providing high-resolution imagery for GIS mapping and spatial analysis.

Earth Observation Satellite Orbit

Earth observation satellites usually use a subsynchronous orbit, which is a special polar orbit that combines elements of a sun-synchronous orbit and a subsynchronous orbit.

Sun-synchronous orbit: In this orbit, the satellite’s orbital plane maintains a constant angle relative to the Sun as viewed from Earth, ensuring that the satellite always passes over the same area at the same solar time.

Subrecursive orbit: This orbit allows the satellite to revisit the same location on the Earth’s surface at regular intervals, maintaining the same local solar time.

A geostationary orbit enables a satellite to observe the same area at regular intervals because the angle of sunlight hitting the Earth’s surface remains nearly constant.

Applications of Earth Observation Satellites

The satellites are based on sensors on Earth observation satellites and provide data at multiple spatial, spectral and temporal resolutions. According to ISRO, the data from these satellites can be used for agriculture, water resources, urban planning, rural development, mineral exploration, environment, forestry, marine resources and disaster management.

According to JAXA, data from Earth observation satellites are also used for aerosol forecasts, studying greenhouse gas emissions, typhoon and rainfall updates, marine pollution, drift ice conditions, sea surface temperature and phytoplankton density, inundation areas caused by earthquakes, floods and tsunamis, volcanic activity, deforestation, land use, vegetation, topography and surface temperature.

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Navigation Satellite

Navigation system constellations are located at altitudes between 20,000 and 37,000 km above the Earth’s surface. These satellites transmit signals that provide information about their position in time, space, and operational status. There are two main types of space navigation systems:

The Global Navigation Satellite System (GNSS) consists of satellites that transmit signals that are received by GNSS receivers and used for geolocation, providing global coverage. Well-known GNSS systems include GPS (USA), GLONASS (Russia), Galileo (Europe) and BeiDou (China).

On the other hand, Regional Navigation Satellite Systems (RNSS) are autonomous systems designed to provide navigation services for a specific region.

Navigation satellite orbit

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Medium Earth Orbit (MEO) carries GPS satellites approximately 20,200 km from Earth.

Geostationary and geosynchronous orbits are key components of NavIC (Navigation of India Constellation), which consists of seven satellites. Three of the satellites are in geostationary orbit and the remaining four are in inclined geosynchronous orbit.

Application of navigation satellites

To meet the country’s positioning, navigation and timing requirements, the Indian Space Research Organization has established a regional navigation satellite system called the Navigation of Indian Constellation (NavIC). According to the Indian Space Research Organization, NavIC was previously known as the Indian Regional Navigation Satellite System (IRNSS).

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Astronomical satellite

Astronomical satellites are essentially giant telescopes in orbit that provide clear views without interference from the Earth’s atmosphere. Their infrared imaging technology works effectively, regardless of the temperature of the Earth’s surface. Such satellites provide views ten times clearer than the most powerful ground-based telescopes.

The Hubble Space Telescope is an example of an astronomical satellite in low Earth orbit.

The James Webb Space Telescope (JWST) is the largest and most powerful telescope ever built, designed to observe distant regions of the universe.

AstroSat is India’s first dedicated astronomical research mission, a space telescope focused on studying celestial objects in the X-ray, optical and ultraviolet spectral bands simultaneously.

Application of astronomical satellites

Astronomical satellites are used to explore a variety of objects and phenomena in space, from creating maps of stars and planetary surfaces to capturing images of solar system planets and studying black holes.

Climate research satellites equipped with specialized sensors enable scientists to collect extensive, multifaceted data on Earth’s oceans, ice, land, biosphere and atmosphere.

Biosatellites facilitate space research into plant and animal cells and structures, playing a vital role in advancing medicine and biology by facilitating collaboration between scientists around the world.

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Category: Optical Illusion