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Satellites in Remote Sensing: Working and Its Types

Last updated on July 20th, 2023 at 06:36 pm

What is the Role Of Satellite in Remote Sensing? 

Satellites are important in Remote Sensing to acquire information about the Earth’s surface without getting into direct contact with it. Satellites that are equipped with various sensors, revolve around the Earth and collect information about the atmosphere, surface and the ocean. Based on the Orbits the satellites follow and the functions of the satellites, The types of Satellite in Remote Sensing are, 

  • Geostationary Satellites
  • Polar-orbiting Satellites
  • Sun-Synchronous Satellites
  • Low Earth Orbit (LEO) Satellites
  • Medium Earth Orbit (MEO) Satellites
  • Radar Satellites
  • Communication Satellites
  • Earth Observation Satellites
  • Navigation Satellites
  • Astronomical Satellites

Geostationary Satellites

Geostationary Satellites are satellites that are positioned in geosynchronous orbit which means that they revolve around the earth at the same speed as the earth rotating itself. Therefore, it looks like the satellite is locked in a position pointing towards the earth. The position for synchronization is approximately 35,786 kilometers ( 22236 Miles ) above the Earth’s equator. 

Since these satellites lock themselves to a specific location pointing the earth, these are great for providing coverage of a particular area. Thus, making it commonly used in weather monitoring, communication and TV broadcasting purposes. 

Pros

  • Continuous coverage and real-time monitoring of a specific region.
  • Wide area coverage, suitable for tracking weather patterns and cloud cover.
  • Stable imaging conditions with consistent lighting and viewing angles.
  • Rapid data availability due to proximity to ground stations.

Cons

  • Lower spatial resolution compared to satellites in lower orbits.
  • Limited spectral bands, which may restrict detailed information capture.
  • Restricted coverage limited to a specific region.
  • Complex and expensive to build and launch.

Polar-orbiting Satellites

A Polar-orbiting Satellite travels in a vertical path around the earth from north to south orbit or vice-versa, passing over the poles of the Earth. These types of satellites usually operated at an altitude between 700 to 1400 Kilometer ( 434 to 869 Miles ).

These satellites provide a global coverage as they pass over the pole, everytime different parts of the earth is covered due to the Earth’s rotation. These satellites are commonly used for weather forecasting, environmental monitoring, and collecting high-resolution imagery.

Pros

  • Global coverage for comprehensive monitoring and data collection.
  • High spatial resolution for detailed mapping and object identification.
  • Diverse sensor payloads for multi-sensor observations.
  • Flexibility in orbit parameters for customized mission requirements.

Cons

  • Longer revisit times compared to geostationary satellites.
  • Weather dependency can impact visibility and data acquisition.
  • Data latency due to downloading and processing requirements.
  • Limited continuous monitoring of a specific area.

Sun-Synchronous Satellites

Sun-Synchronous Satellites are the polar orbiting satellites but they maintain a constant angle between the orbital plane and the direction of the sun when revolving around the earth. This is done in order to make sure the sun’s light falls on the earth constantly when collecting the data. 

These satellites are widely used for land mapping, vegetation monitoring and climate studies in remote sensing. Due to the nature of collecting data in the sun side, these satellites provide highly accurate and consistent imagery at different times. 

Pros

  • Consistent lighting conditions for accurate and consistent data acquisition.
  • Global coverage for comprehensive monitoring and data collection.
  • Suitable for long-term monitoring and comparison of imagery captured at different times.
  • Alignment with specific solar angles facilitates targeted observations and analysis.

Cons

  • Longer revisit times compared to geostationary satellites.
  • Limited flexibility in orbit parameters compared to polar-orbiting satellites.
  • Weather conditions can still impact visibility and data acquisition.
  • Not suitable for continuous real-time monitoring of a specific area.

Low Earth Orbit (LEO) Satellites

Low Earth Orbit (LEO) Satellites operate below the altitude of 2000 kilometers ( 1242 miles ) and they typically orbit around the earth relatively fast within a couple of hours.  Since the lower altitude of these satellites, these are used for mapping, disaster monitoring and tracking environmental changes in remote sensing. 

Pros

  • High spatial resolution for detailed imaging and object identification.
  • Short revisit times for frequent observations of specific areas.
  • Versatile and adaptable for various remote sensing applications.
  • Lower signal delay due to the proximity to the Earth’s surface.

Cons

  • Limited coverage compared to geostationary or polar-orbiting satellites.
  • Higher data acquisition and processing requirements due to the frequent imaging.
  • Limited endurance and shorter mission lifespans compared to satellites in higher orbits.
  • More complex constellation management for ensuring continuous coverage.

Medium Earth Orbit (MEO) Satellites

Medium Earth Orbit (MEO) Satellites are positioned at higher altitudes compared to the LEO satellites. They are typically positioned between 2000 and 35786 kilometers ( 1242 to 22236 Miles ) above the earth surface.  

These MEO satellites are commonly used for the navigation systems like the GPS ( Global Positioning System ), where they can be used for applications such as geodetic data collection or monitoring large scale environmental changes. 

Pros

  • Provides global coverage with wider area observation compared to LEO satellites.
  • Enables accurate and reliable positioning and navigation services.
  • Offers a balance between coverage and signal strength.
  • Can be used for remote sensing and geodetic data collection.

Cons

  • Higher latency compared to LEO satellites for data transmission.
  • More limited spatial resolution compared to LEO or geostationary satellites.
  • Higher cost and complexity compared to LEO satellites.
  • Longer orbital period leads to lower revisit times compared to LEO satellites.

Radar Satellites

Radar Satellites use active sensors that emit microwave pulses and measure the signal that gets scattered back after hitting an object and creating an image by calculating the TOF ( Time Of Flight ). Since radars are not affected by clouds and can penetrate through them, Radar satellites are used in mapping terrains, monitoring glaciers and detecting changes in land cover. 

Pros

  • All-weather capability and ability to penetrate clouds and vegetation.
  • Day and night imaging for continuous monitoring.
  • Mapping and monitoring surface deformation over time.

Cons

  • Lower spatial resolution compared to optical satellites.
  • Limited spectral information.
  • Complex data interpretation.
  • Higher cost and technical complexity.

Communication Satellites

Communication satellites are satellites that are used for transmitting and receiving signals for long distance communications. It operates in Geostationary orbit or any other suitable orbit and is equipped with a transmitter, receiver and amplifier to provide effective communication among places on earth. 

These satellites are commonly used for military purposes, Television broadcasting, telephone network and Internet connectivity in remote places. 

Pros

  • Global coverage for communication services, enabling connectivity in remote areas.
  • Wide bandwidth capacity for high-speed data transmission and telecommunications.
  • Facilitates long-distance and international communication, including voice, data, and multimedia.
  • Enables broadcasting services, including television and radio, to reach a wide audience.

Cons

  • Vulnerable to signal interference and disruptions, impacting communication quality.
  • Limited signal bandwidth can lead to congestion and slower speeds during peak usage.
  • Expensive infrastructure and maintenance costs for satellite communication systems.
  • Requires proper positioning and alignment for effective communication.

Earth Observation Satellites

Earth Observation Satellites are mainly used in collecting information about the Earth’s Surface, Atmosphere and Ocean. The data collected by these satellites are mainly used in remote sensing applications such as mapping, land cover, vegetation, monitoring and other purposes.

These satellites collect this information with the help of various sensing equipment such as the LiDAR, Radar and spectrometer etc. 

Pros

  • Provides global coverage for monitoring and studying the Earth’s surface, atmosphere, and oceans.
  • Enables comprehensive mapping, land cover monitoring, and environmental assessment.
  • Supports disaster management, climate studies, and scientific research.
  • Facilitates resource management, urban planning, and agriculture monitoring.

Cons

  • Limited spatial resolution for detailed analysis compared to higher-resolution sensors.
  • Weather conditions can impact image quality and data acquisition.
  • Costly to develop, launch, and maintain satellite systems.
  • Data processing and analysis may require specialized expertise and resources.

Navigation Satellites

Navigation Satellites are mostly MEO satellites orbiting the earth in medium earth orbits. These satellites are mainly used for navigation purposes such as GPS systems. These satellites are clustered to provide a highly accurate location on the surface of the earth with the method of Triangulation. 

Pros

  • Enables precise positioning, navigation, and timing services worldwide.
  • Supports various applications such as transportation, logistics, and emergency response.
  • Provides continuous coverage, even in remote areas or areas with limited ground-based infrastructure.
  • Facilitates accurate mapping and surveying operations.

Cons

  • Signal reception can be affected by physical obstructions such as buildings, trees, or terrain.
  • Vulnerable to signal interference, including intentional jamming or unintentional signal degradation.
  • Limited accuracy in certain environments, such as dense urban areas or deep valleys.
  • Reliance on satellite constellations, requiring continuous maintenance and updates.

Astronomical Satellites

Astronomical Satellites uses highly reflective mirrors and other sensors to study the structure and map of the universe. These are mainly used for cosmology studies where the details of the universe and the phenomenals happening in the universe are observed and studied. 

Pros

  • Enables observations of celestial objects and phenomena beyond the Earth’s atmosphere.
  • Provides a clear view of the Universe, unaffected by atmospheric distortions.
  • Enables long-duration observations, allowing for continuous monitoring of cosmic events.
  • Offers access to specific wavelengths or frequencies not easily observable from the Earth’s surface.

Cons

  • Limited field of view compared to ground-based telescopes.
  • Higher cost and complexity of building and maintaining astronomical satellite systems.
  • Limited payload capacity for instruments and telescopes due to weight and size constraints.
  • Challenges associated with data transmission and storage from distant astronomical satellites.

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