Remote sensing & Radiometers Systems
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The document presents a comprehensive overview of microwave radiometer systems, covering aspects such as remote sensing, types of radiometers, and their principles of operation. It details active and passive remote sensing methods, highlighting the applications and design of microwave radiometers while pointing out the differences between passive and active systems. Additionally, it discusses specific types of radiometers and their significance in environmental monitoring and research.
Remote sensing & Radiometers Systems
- 1. Laxmi Institute of Technology, Sarigam Department of Electronics & Communication Engineering (7 SEM) SUB: Microwave Engineering (2171001) Presentation On Radiometers Systems Submitted by:- Name: EnrollnmentNo. Jay Baria 150860111003 Approved by AICTE, New Delhi; Affiliated to Gujarat Technological University, Ahmedabad
- 2. Content • Remote sensing • Types of Remote sensing • Active Remote sensing • Passive Remote sensing • Radiometers • Principle of operation • Design • Types of Radiometers
- 3. Remote Sensing: • It is a technique with good potential to help the nations economic growth and solve some of its problems. • It includes better management of natural resources like, 1. Wasteland mapping 2. Identifying flood prone area 3. Estimating forest area
- 4. Types of Remote Sensing : 1. Active microwave remote sensing 2. Passive microwave remote sensing
- 5. Active Remote Sensing • It uses active sensors like camera to sense the natural calamities • The main advantage is that we can retrieve the information at any time i.e, day, night or any season.
- 6. Passive Remote Sensing • Passive microwave remote sensing are known as radiometers. They sense natural radiations originating from earth surface. • This sensing is also known as atmospheric sounding. • The atmospheric sounding gives vertical profile of temperature & molecular constituents with respect to the molecular resonance frequency.
- 7. Radiometers • Microwave radiometers are very sensitive receivers designed to measure thermal electromagnetic radiation emitted by atmospheric gases. • Microwave radiometers are utilized in a variety of environmental and engineering applications, includes weather forecasting, climate monitoring, radio astronomy and radio propagation studies. • It performance depends on the object size, different obstacles in the path of signal, atmosphere temperature.
- 8. Principle of operation • Solids, liquids but also gases emit and absorb microwave radiation. • The amount of radiation a microwave radiometer receives is expressed as the equivalent blackbody temperature also called brightness temperature. • In the microwave range several atmospheric gases exhibit rotational lines. • They provide specific absorption features which allow to derive information about their abundance and vertical structure.
- 9. Radiometer Applications • Soil moisture • Snow water equivalent • Sea/lake ice extent, concentration and type • Sea surface temperature • Atmospheric water vapor • Surface wind speed • Cloud liquid water • Rainfall rate only over the oceans
- 10. Difference between Passive and Active Systems • Passive remote sensing systems record electromagnetic energy that is reflected or emitted from the Earth’s surface and atmosphere • Active sensors create their own electromagnetic energy that 1) is transmitted from the sensor toward the terrain, 2) interacts with the terrain producing a backscatter of energy 3) is recorded by the remote sensor’s receiver.
- 11. Design
- 12. Design • A microwave radiometer consists of an antenna system, microwave radio-frequency components (front-end) and a back-end for signal processing at intermediate frequencies. • The atmospheric signal is very weak and the signal needs to be amplified by around 80 dB. • Therefore, often heteorodyne techniques are used to convert the signal down to lower frequencies that allow the use of commercial amplifiers and signal processing. Increasingly low noise amplifiers become available at higher frequencies, i.e. up to 100 GHz, making heteorodyne techniques obsolete. • Thermal stabilization is highly important to avoid receiver drifts.
- 13. Types of Radiometers 1. Total power radiometer 2. Dicke radiometer 3. Satellite borne radiometer 4. Pushbroom and synthetic aperture radiometer
- 14. Dicke Radiometer • The most common form of microwave radiometer was introduced by Robert Dicke in 1946 in the radiation laboratory of Massachusetts Institute of Technology to better determine the temperature of the microwave background radiation.
- 15. Synthetic-aperture radiometers •The underlying idea of the synthetic-aperture radiometer is that with an array of receiving elements, multiple beams can be formed simultaneously to image a swath. •This is accomplished by cross-correlated signals from a pair of antennas with overlapping fields of view.
- 16. Satellite Borne radiometer •Soil moisture is a key factor in determining humidity in the atmosphere and the formation of precipitation. These data will also aid researchers studying plant growth and vegetation distributions. An artist's concept of the Soil and Moisture Observation Satellite (SMOS) satellite with deployed solar arrays and instrument
- 17. Satellite borne radiometer •These radiometer operates in the L-band of the electromagnetic spectrum in a band (1400-1427 MHz) reserved (by the International Telecommunications Union) for space research, radio astronomy and a radio communication service between Earth stations and space, known as the Earth Exploration Satellite Service. •Since its 2009 launch and system check out, project scientists noticed that over certain areas the MIRAS radiometer data were badly contaminated by radio-frequency interference (RFI). •The unwanted signals have mainly come from TV transmitters, radio links and networks such as security systems. Terrestrial radars appear to also cause some problems.
- 18. Satellite radiometer data •March 2010 SMOS image from, over Spain
- 19. Microwave Radiometer Ground-Based Networks: • MWRnet is a network established in 2009 of scientists working with ground-based microwave radiometers. • MWRnet aims to facilitate the exchange of information in the MWR user community fostering the participation to coordinated international projects. • In the long run, MWRnet’s mission aims at setting up operational software, quality control procedures, data formats, etc. Similar to other successful networks.
- 20. References • www.google.co.in • www.slideshare.com • www.wikipidia.com
- 21. Thank you!