Microwave Remote Sensing

Active and passive microwave remote sensing are two distinct methods used in the field of remote sensing to collect information about the Earth's surface and atmosphere using microwave radiation. Let's explore the principles of each:

1. Active Microwave Remote Sensing:

- Principle: Active microwave remote sensing involves the transmission of microwave pulses from a sensor or satellite to the Earth's surface. These pulses are then reflected or scattered back to the sensor, where they are received and analyzed to gather information about the target area.

- Key Features:

- Microwave Source: An active microwave sensor emits microwave radiation (usually in the form of radar pulses) towards the Earth.

- Reflection and Scattering: When the microwave pulses encounter objects on the Earth's surface, they interact with them. Some of the energy is reflected back to the sensor, while the rest is scattered.

- Distance Measurement: By measuring the time it takes for the microwave pulses to travel to the target and return (time-of-flight), active microwave remote sensing can calculate the distance to the target.

- Applications: Active microwave remote sensing is used for applications such as topographic mapping, vegetation monitoring, and soil moisture estimation. Synthetic Aperture Radar (SAR) is a common example of an active microwave sensor.

2. Passive Microwave Remote Sensing:

- Principle: Passive microwave remote sensing, on the other hand, relies on the detection of naturally occurring microwave radiation emitted or scattered by the Earth's surface and atmosphere. Instead of actively transmitting microwave signals, passive sensors measure the microwave radiation already present.

- Key Features:

- Microwave Receiver: Passive microwave sensors have specialized receivers that can detect microwave emissions from the Earth.

- Spectral Bands: These sensors are sensitive to specific microwave frequencies or spectral bands, which correspond to different properties of the Earth's surface or atmosphere.

- Applications: Passive microwave remote sensing is often used for monitoring atmospheric conditions (e.g., weather forecasting), sea surface temperature, sea ice concentration, and soil moisture. It is particularly valuable for studying the Earth's energy balance.

In summary, active microwave remote sensing involves sending out microwave pulses and measuring their reflections or scattering, while passive microwave remote sensing relies on naturally emitted or scattered microwave radiation. Each method has its unique applications and advantages, making them valuable tools for Earth observation and scientific research.

Comments

geostationary and sun-synchronous

Orbital characteristics of Remote sensing satellite geostationary and sun-synchronous Orbits in Remote Sensing Orbit = the path a satellite follows around the Earth. The orbit determines what part of Earth the satellite can see , how often it revisits , and what applications it is good for . Remote sensing satellites mainly use two standard orbits : Geostationary Orbit (GEO) Sun-Synchronous Orbit (SSO) Geostationary Satellites (GEO) Characteristics Altitude : ~35,786 km above the equator. Period : 24 hours → same as Earth's rotation. Orbit type : Circular, directly above the equator . Appears "stationary" over one fixed point on Earth. Concepts & Terminologies Geosynchronous = orbit period matches Earth's rotation (24h). Geostationary = special type of geosynchronous orbit directly above equator → looks fixed. Continuous coverage : Can monitor the same area all the time. Applications Weather...

Disaster Management

1. Disaster Risk Analysis → Disaster Risk Reduction → Disaster Management Cycle Disaster Risk Analysis is the first step in managing disasters. It involves assessing potential hazards, identifying vulnerable populations, and estimating possible impacts. Once risks are identified, Disaster Risk Reduction (DRR) strategies come into play. DRR aims to reduce risk and enhance resilience through planning, infrastructure development, and policy enforcement. The Disaster Management Cycle then ensures a structured approach by dividing actions into pre-disaster, during-disaster, and post-disaster phases . Example Connection: Imagine a coastal city prone to cyclones: Risk Analysis identifies low-lying areas and weak infrastructure. Risk Reduction includes building seawalls, enforcing strict building codes, and training residents for emergency situations. The Disaster Management Cycle ensures ongoing preparedness, immediate response during a cyclone, and long-term recovery afterw...

Linear Arrays Along-Track Scanners or Pushbroom Scanners

Multispectral Imaging Using Linear Arrays (Along-Track Scanners or Pushbroom Scanners) Multispectral Imaging: As previously defined, this involves capturing images using multiple sensors that are sensitive to different wavelengths of electromagnetic radiation. Linear Array of Detectors (A): This refers to a row of discrete detectors arranged in a straight line. Each detector is responsible for measuring the radiation within a specific wavelength band. Focal Plane (B): This is the plane where the image is formed by the lens system. It is the location where the detectors are placed to capture the focused image. Formed by Lens Systems (C): The lens system is responsible for collecting and focusing the incoming radiation onto the focal plane. It acts like a camera lens, creating a sharp image of the scene. Ground Resolution Cell (D): As previously defined, this is the smallest area on the ground that can be resolved by a remote sensing sensor. In the case of linear array scanne...

Discrete Detectors and Scanning mirrors Across the track scanner Whisk broom scanner.

Multispectral Imaging Using Discrete Detectors and Scanning Mirrors (Across-Track Scanner or Whisk Broom Scanner) Multispectral Imaging: This technique involves capturing images of the Earth's surface using multiple sensors that are sensitive to different wavelengths of electromagnetic radiation. This allows for the identification of various features and materials based on their spectral signatures. Discrete Detectors: These are individual sensors that are arranged in a linear or array configuration. Each detector is responsible for measuring the radiation within a specific wavelength band. Scanning Mirrors: These are optical components that are used to deflect the incoming radiation onto the discrete detectors. By moving the mirrors, the sensor can scan across the scene, capturing data from different points. Across-Track Scanner or Whisk Broom Scanner: This refers to the scanning mechanism where the mirror moves perpendicular to the direction of flight. This allows for t...

Vineesh V, Geography

Search This Blog