Orbiting Satellites and Sensor Systems | Geology Optional for UPSC PDF Download

Remote Sensing Platforms

Definition: Platforms serve as vehicles or carriers for remote sensing devices, facilitating observations.

Types of Platforms

Terrestrial Platforms

• Include tripods, booms, cranes, and towers as examples.
• Booms elevate sensors 1 to 2 meters above the target, while towers can extend tens of meters high.

Airborne Platforms

• Consist of helicopters, light planes, high-flying aircraft, and aerial photography systems.
• Helicopters and planes operate at lower altitudes, while high-flying aircraft cover greater areas.

Spaceborne Platforms

• Include satellites equipped with optical sensors and Synthetic Aperture Radar (SAR).
• Satellites orbit at altitudes of 185-900 kilometers, providing wide coverage.

Selection Criteria for Platforms

• Altitude determines ground coverage; higher altitudes capture larger areas.
• Various parameters influence ground coverage and image resolution.
• Different sensors on a single platform can acquire data at varying resolutions and coverage areas.

Sensors and Platforms for Remote Sensing

Ground-based Platforms:

• Static Platforms: Fixed on stationary structures like tripods or masts.
• Dynamic Platforms: Mounted on moving vehicles.
• Operate at short (50-100m), medium (up to 250m), and long ranges (up to 1000m).
  • Short-range: Mapping buildings and small objects.
  • Medium-range: 3D modeling with millimeter accuracy.
  • Long-range: Topographic purposes.
• Provide high spatial resolution images compared to aerial or satellite platforms.
• Applications: Bridge monitoring, landslide mapping, architectural restoration, and more.

Airborne Platforms:

• Originated with photographic cameras and evolved to advanced sensor technology.
• Include airplanes, helicopters, balloons, and rockets, operating at various altitudes.

Advantages

• Flying at low altitudes for high sensor spatial resolution.
• Flexibility to avoid weather disturbances.
• Ease of sensor maintenance and configuration changes.
• Adjustable schedules for lighting conditions and revisiting locations.
• Aerial photographs provide detailed Earth surface information.

Metrology

• Encompasses the theoretical and practical aspects of measurement.
• Ensures accurate measurements across various fields and industries.

Sensors and Space Programmes

Spaceborne Platforms

• Definition: Refer to man-made satellites and space shuttles used for various purposes.
• Examples: Satellites for remote sensing, communication, and navigation.
• Orbits: Geostationary, polar, and sun-synchronous orbits.

Duration

• Short-term: Space shuttles.
• Long-term: Earth monitoring satellites like Landsat.

• Applications: Weather prediction, crop monitoring, mineral exploration, etc.

Advantages of Spaceborne Remote Sensing

• Allows large area coverage.
• Offers frequent and repetitive coverage.
• Enables quantitative measurements using calibrated sensors.
• Supports semi-automated processing and analysis.
• Cost-effective in terms of coverage per unit area.
• Global accessibility without airspace restrictions.

Platform Selection

• Ground-based platforms: Detailed 3D modeling of structures.
• Airborne platforms: Topographic mapping.
• Spaceborne systems: Global accessibility and large-scale coverage.

Satellite Remote Sensing

• Crucial for mapping remote areas for scientific purposes.
• Increasingly used for topographic and cartographic applications.
• Decision-making influenced by data acquisition cost and desired information.

Platforms Used in Remote Sensing

• Satellites
• Aircraft
• Drones
• Balloons

Advantages of Aerial Platforms:

• High spatial resolution
• Quick data acquisition

Astronomical Satellites

• Function as telescopes in space, providing clearer vision compared to Earth-based telescopes due to lack of atmospheric interference.

Types of Satellites

• Astronomical, communication, weather, remote sensing, navigation, and reconnaissance.

Applications of Astronomical Satellites

• Creating star maps
• Studying celestial phenomena like black holes and quasars
• Mapping planetary surfaces

Hubble Space Telescope

• Launched in 1990, named after astronomer Edwin Hubble.
• Studies celestial objects with high precision and versatility.

Communication Satellites

• Facilitate telephonic conversations, television broadcasts, FAX services, and more over long distances.
• Positioned in geostationary orbits.
• Play a vital role in daily activities like watching TV, making calls, and using fax machines.
• Function as radio relay stations in space.

Weather Satellites

• Monitor and forecast weather patterns worldwide.

• Provide insights on radiation measurements, snow cover, ice movement, ocean depth, crop conditions, deforestation, and drought regions.

Earth Observation Satellites

• Observe and measure Earth's environment from afar.
• Reveal features like animal migration, mineral deposits, agricultural conditions, etc.

Applications of Satellites

• Monitoring remote or harsh environments.

Navigation Satellites

• Aid in precise location tracking, especially for ships.
• GPS enables accurate positioning on Earth's surface.

Reconnaissance Satellites

• Gather intelligence on military activities of foreign nations.
• Detect missile launches, nuclear explosions, and intercept signals.

Orbits and Their Types

Understanding Orbits

• Path a satellite follows while revolving around Earth.
• Orbital plane: Specific plane in which a satellite moves.
• Orbital period: Time taken to complete one orbit.

Types of Orbits:

• Equatorial Orbits: Inclination of 0° or 180°.
• Polar Orbits: Inclination of 90°.
• Inclined Orbits: Inclinations between 0° and 90°.

Ascending and Descending Passes:

• Ascending: South to north.
• Descending: North to south.

Field of View (FOV):

• Defines the swath or area observed by the sensor.
• Polar orbiting satellites image most of Earth's surface.

Orbital Characteristics:

• Sunsynchronous satellites orbit at 700-800 km altitudes.
• Ensure consistent illumination conditions for comparisons.

Advantages of Sunsynchronous Orbits:

• Consistent shadows simplify image comparison.

Examples of Satellites:

• Orbview, Quickbird, IKONOS, SPOT, Landsat, ERS, RADARSAT.

Dawn-to-Dusk Orbit:

• Aligns with the division between Sunlit and dark halves of Earth.

Satellite Sensor Systems Overview

Importance of Satellite Orbits

• Dawn-to-dusk orbits provide constant solar illumination.
• Applications include Earth observation, solar studies, and weather forecasting.

Sensor Systems on Satellites

• Operate in visible, infrared, thermal, and microwave regions.
• Imaging vs. non-imaging sensors.
• Passive sensors detect natural EMR; active sensors detect artificial sources like RADAR.

Types of Remote Sensing Sensors

• Active Sensors: Thermal, microwave, and optical-infrared sensors.
• Passive Sensors: Optical-infrared sensors recording reflected energy.

Examples of Sensors

• MKF-6M, Bhaskara-1, Landsat MSS, INSAT, RADARSAT SAR.

Thermal Infrared Scanners

• Capture radiant temperature variations emitted by objects.
• Operate both day and night.

Types of Thermal Infrared Scanners

• HCMM, TIMS, MODIS, ASTER, AVHRR.

Microwave Imaging Systems

• Cover wavelengths from 1mm to 1m.
• Active systems include SLAR; passive systems measure natural energy.

Summary and Explanation of Remote Sensing Systems

• Side Looking Airborne Radar (SLAR): Provides a view of terrain or moving targets.
• Thermal Sensors: Measure surface temperature and thermal properties.
• Microwave Imaging System: Offers advantages like penetrating clouds and smoke, operating day and night.
• Advanced Thermal Infrared Scanners: Used for geologic mapping, soil moisture determination, and urban temperature analysis.
• Multispectral Imaging Sensor Systems: Capture a wide range of wavelengths for high resolution and minimal distortion.

Definitions

• IFOV: Patch of landscape visible to a detector.
• Ground Resolution Cell: Area covered by detector's IFOV.
• Dwell Time: Duration for IFOV to sweep a resolution cell.