Skip to main content

Unmanned Earth Resources Satellites


Unmanned Earth resources satellites are satellites equipped with remote sensing instruments used to collect images and environmental data from the Earth's surface without a crew onboard.
They help monitor:

  • land use

  • vegetation

  • soil and water resources

  • climate

  • oceans

  • atmosphere

  • natural hazards

These satellites are grouped based on the type of radiation they measure and the sensors they carry.

Five Groups of Unmanned Earth Resources Satellites

Remote sensing satellites can be categorized into five main groups, based on the wavelengths they record and the type of environmental information they collect.

First-Generation Earth Resources Satellites

Wavelength region: Visible and Near-Visible (VNIR)

✔ Characteristics

  • Use multispectral scanners

  • Record reflected sunlight

  • Mainly for land use, vegetation, and surface mapping

✔ Example

  • Landsat series (Landsat 1, 2, 3)
    These were the first generation of Earth resource satellites launched in the 1970s.

Second-Generation Earth Resources Satellites

Wavelength region: Visible and Near-Visible (VNIR)

✔ Characteristics

  • Improved spatial resolution

  • More spectral bands

  • Higher radiometric sensitivity

✔ Examples

  • SPOT (Satellite Pour l'Observation de la Terre)

  • Later Landsat missions (Landsat 4, 5, 7)

SPOT introduced high-resolution panchromatic imagery and along-track stereo capability, which greatly advanced remote sensing.

Thermal Infrared Satellites

Wavelength region: Thermal Infrared (TIR)

✔ Characteristics

  • Measure emitted heat energy

  • Useful for temperature mapping

  • Work both day and night

✔ Examples

  • HCMM (Heat Capacity Mapping Mission)
    A NASA mission designed to study thermal behavior of land surfaces.

Microwave Remote Sensing Satellites

Wavelength region: Microwave (active or passive)

✔ Characteristics

  • Can penetrate clouds, smoke, and light rain

  • Work day and night

  • Include both active radar and passive microwave sensors

✔ Examples

  • Seasat (first ocean-related radar satellite)

  • ERS-1 (European Remote Sensing Satellite)

  • RADARSAT (Canadian radar satellite)

These satellites are extremely useful for:

  • flood mapping

  • soil moisture

  • sea-ice monitoring

  • land deformation (InSAR)

Polar Platform Satellites

Orbit: Polar orbit / Sun-synchronous orbit

✔ Characteristics

  • Carry a wide range of multispectral, thermal, microwave, and atmospheric sensors

  • Provide continuous, long-term environmental monitoring

  • Serve as major data sources for climate and environmental studies

✔ Examples

  • NOAA Polar Orbiters

  • EOS (Earth Observing System) satellites such as:

    • Terra

    • Aqua

    • Aura

These satellites will continue to provide vital environmental data well into the future.


GroupWavelengthsPurposeExamples
1Visible + NIRFirst-generation multispectral satellitesLandsat 1–3
2Visible + NIRSecond-generation multispectral satellitesSPOT, Landsat 4–7
3Thermal IRHeat and temperature mappingHCMM
4MicrowaveRadar and microwave sensingSeasat, ERS-1, Radarsat
5Polar PlatformsMultisensor environmental observationTerra, Aqua, Aura, NOAA


Unmanned Earth resources satellites are remote sensing platforms carrying different sensors to monitor Earth's surface. They are grouped into five types based on the wavelengths they detect: visible/NIR (Landsat, SPOT), thermal (HCMM), microwave (Seasat, ERS-1, RADARSAT), and multisensor polar platforms (Terra, Aqua, NOAA). These satellites provide critical environmental data for physical geography and Earth science.


Comments

Post a Comment

Popular posts from this blog

Energy Interaction with Atmosphere and Earth Surface

In Remote Sensing , satellites record electromagnetic radiation (EMR) that is reflected or emitted from the Earth. Before reaching the sensor, radiation interacts with: The Atmosphere The Earth's Surface These interactions control how satellite images look and how we interpret them. I. Interaction of EMR with the Atmosphere When solar radiation travels from the Sun to the Earth, four main processes occur: 1. Absorption Definition: Absorption occurs when atmospheric gases absorb radiation at specific wavelengths and convert it into heat. Main absorbing gases: Ozone (O₃) → absorbs Ultraviolet (UV) Carbon dioxide (CO₂) → absorbs Thermal Infrared Water vapour (H₂O) → absorbs Infrared Concept: Atmospheric Windows These are wavelength regions where absorption is very low, allowing radiation to pass through the atmosphere. Remote sensing depends on these windows. For example, satellites like Landsat 8 use visible, near-infrared, and thermal bands located in atmospheric windows. 2. Trans...
Post a Comment
Read more

Types of Remote Sensing

Remote Sensing means collecting information about the Earth's surface without touching it , usually using satellites, aircraft, or drones . There are different types of remote sensing based on the energy source and the wavelength region used. 🛰️ 1. Active Remote Sensing 📘 Concept: In active remote sensing , the sensor sends out its own energy (like a signal or pulse) to the Earth's surface. The sensor then records the reflected or backscattered energy that comes back from the surface. ⚙️ Key Terminology: Transmitter: sends energy (like a radar pulse or laser beam). Receiver: detects the energy that bounces back. Backscatter: energy that is reflected back to the sensor. 📊 Examples of Active Sensors: RADAR (Radio Detection and Ranging): Uses microwave signals to detect surface roughness, soil moisture, or ocean waves. LiDAR (Light Detection and Ranging): Uses laser light (near-infrared) to measure elevation, vegetation...
Post a Comment
Read more

Platforms in Remote Sensing

In remote sensing, a platform is the physical structure or vehicle that carries a sensor (camera, scanner, radar, etc.) to observe and collect information about the Earth's surface. Platforms are classified mainly by their altitude and mobility : Ground-Based Platforms Definition : Sensors mounted on the Earth's surface or very close to it. Examples : Tripods, towers, ground vehicles, handheld instruments. Applications : Calibration and validation of satellite data Detailed local studies (e.g., soil properties, vegetation health, air quality) Strength : High spatial detail but limited coverage. Airborne Platforms Definition : Sensors carried by aircraft, balloons, or drones (UAVs). Altitude : A few hundred meters to ~20 km. Examples : Airplanes with multispectral scanners UAVs with high-resolution cameras or LiDAR High-altitude balloons (stratospheric platforms) Applications : Local-to-regional mapping ...
Post a Comment
Read more

Government of Kerala Initiatives for Water Management

Kerala, with its abundant rainfall and network of rivers, faces a dual challenge of water scarcity and excess —seasonal droughts and monsoon floods. The state government has implemented various policies and programs to address these challenges through sustainable water conservation, management, and distribution practices . Below is a detailed breakdown of the major water management initiatives in Kerala. 1. Jal Jeevan Mission (JJM) – Kerala Implementation Objective: To provide functional household tap connections (FHTC) to all rural households by 2024. Focuses on source sustainability and community-led water resource management. Key Features: Water Quality Monitoring & Surveillance: Ensures supply of safe drinking water through real-time monitoring. Decentralized Approach: Implementation through gram panchayats and local self-governments (LSGs) . Recharge & Conservation Measures: Rainwater harvesting, groundwater recharge, and watershed development inte...
Post a Comment
Read more

Atmospheric Window

The atmospheric window in remote sensing refers to specific wavelength ranges within the electromagnetic spectrum that can pass through the Earth's atmosphere relatively unimpeded. These windows are crucial for remote sensing applications because they allow us to observe the Earth's surface and atmosphere without significant interference from the atmosphere's constituents. Key facts and concepts about atmospheric windows: Visible and Near-Infrared (VNIR) window: This window encompasses wavelengths from approximately 0. 4 to 1. 0 micrometers. It is ideal for observing vegetation, water bodies, and land cover types. Shortwave Infrared (SWIR) window: This window covers wavelengths from approximately 1. 0 to 3. 0 micrometers. It is particularly useful for detecting minerals, water content, and vegetation health. Mid-Infrared (MIR) window: This window spans wavelengths from approximately 3. 0 to 8. 0 micrometers. It is valuable for identifying various materials, incl...
Post a Comment
Read more