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Questions and Answers
What does polarization primarily refer to in radar technology?
What does polarization primarily refer to in radar technology?
Which of the following best describes the function of passive microwave sensors?
Which of the following best describes the function of passive microwave sensors?
What is a significant limitation of passive microwave sensors as compared to optical sensors?
What is a significant limitation of passive microwave sensors as compared to optical sensors?
What is an advantage of using passive microwave sensing over visible/infrared sensors?
What is an advantage of using passive microwave sensing over visible/infrared sensors?
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In what manner do passive microwave sensors typically operate?
In what manner do passive microwave sensors typically operate?
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What is the primary purpose of using synthetic aperture radar (SAR)?
What is the primary purpose of using synthetic aperture radar (SAR)?
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Which statement correctly describes the behavior of radar beams concerning targets at different ranges?
Which statement correctly describes the behavior of radar beams concerning targets at different ranges?
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What key measurement does a satellite altimeter rely on to determine sea level?
What key measurement does a satellite altimeter rely on to determine sea level?
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Which of the following functions is NOT a capability of satellite altimeters?
Which of the following functions is NOT a capability of satellite altimeters?
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What is a typical size range for satellite radar antennas?
What is a typical size range for satellite radar antennas?
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Which instrument uses Ka-band radar for measuring ocean temperature?
Which instrument uses Ka-band radar for measuring ocean temperature?
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What type of energy do passive microwave sensors detect?
What type of energy do passive microwave sensors detect?
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What major obstructions hinder the thermal infrared sensors from acquiring data?
What major obstructions hinder the thermal infrared sensors from acquiring data?
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Which application is primarily associated with high spatial resolution in microwave remote sensing?
Which application is primarily associated with high spatial resolution in microwave remote sensing?
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Which of the following sensors is included in passive microwave remote sensing?
Which of the following sensors is included in passive microwave remote sensing?
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Which aspect of microwave energy is critical for its interaction with materials?
Which aspect of microwave energy is critical for its interaction with materials?
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How does using two bands in water vapor correction improve sea surface temperature calculation?
How does using two bands in water vapor correction improve sea surface temperature calculation?
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In the context of microwave remote sensing, what does SSH stand for?
In the context of microwave remote sensing, what does SSH stand for?
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What is one of the benefits of using sea surface temperature (SST) images?
What is one of the benefits of using sea surface temperature (SST) images?
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Which of the following atmospheric corrections is simpler for infrared compared to ocean corrections?
Which of the following atmospheric corrections is simpler for infrared compared to ocean corrections?
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Which application is NOT typically associated with atmospheric microwave remote sensing?
Which application is NOT typically associated with atmospheric microwave remote sensing?
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Which of the following statements about microwave remote sensing is true?
Which of the following statements about microwave remote sensing is true?
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What does the equation SST = a0 + a1Ti + a2(Ti - Tj) represent?
What does the equation SST = a0 + a1Ti + a2(Ti - Tj) represent?
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What type of microwave remote sensing is characterized by emitted energy?
What type of microwave remote sensing is characterized by emitted energy?
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What does the TI in the equation SST = a0 + a1Ti + a2(Ti - Tj) refer to?
What does the TI in the equation SST = a0 + a1Ti + a2(Ti - Tj) refer to?
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Which of the following is an application of microwave remote sensing related to oceans?
Which of the following is an application of microwave remote sensing related to oceans?
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What is the term used to describe the temperature calculated assuming an object's emissivity is 1.0?
What is the term used to describe the temperature calculated assuming an object's emissivity is 1.0?
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Which principle explains the relationship between the spectral radiance and the temperature of a black body?
Which principle explains the relationship between the spectral radiance and the temperature of a black body?
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What is a significant application of passive microwave sensors?
What is a significant application of passive microwave sensors?
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Why might the radiant temperature (Trad) be lower than the true kinetic temperature (Tkin)?
Why might the radiant temperature (Trad) be lower than the true kinetic temperature (Tkin)?
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What type of satellite provides global coverage and high stability for environmental measurements?
What type of satellite provides global coverage and high stability for environmental measurements?
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Which physical constant is essential in the Rayleigh–Jeans law for calculating spectral radiance?
Which physical constant is essential in the Rayleigh–Jeans law for calculating spectral radiance?
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What method is often used to calculate true ground temperature from radiant temperature?
What method is often used to calculate true ground temperature from radiant temperature?
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What does the relationship between spectral radiance, temperature, and wavelength involve?
What does the relationship between spectral radiance, temperature, and wavelength involve?
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What is the primary use of scatterometers in satellite remote sensing?
What is the primary use of scatterometers in satellite remote sensing?
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Which scatterometer operates with a 50 km spatial resolution?
Which scatterometer operates with a 50 km spatial resolution?
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What is a common application of satellite scatterometers?
What is a common application of satellite scatterometers?
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Which formula is used for calculating daytime MCSST using AVHRR?
Which formula is used for calculating daytime MCSST using AVHRR?
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Which characteristic is NOT shared by the scatterometers listed?
Which characteristic is NOT shared by the scatterometers listed?
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What is the operational frequency characteristic of the HY-2B scatterometer?
What is the operational frequency characteristic of the HY-2B scatterometer?
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Which of the following terms is a component in the MCSST formulas for both AVHRR and MODIS?
Which of the following terms is a component in the MCSST formulas for both AVHRR and MODIS?
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What does the 'sec(ө)' term in the MCSST formulas represent?
What does the 'sec(ө)' term in the MCSST formulas represent?
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Study Notes
Microwave Remote Sensing Basics
- Microwave remote sensing utilizes electromagnetic radiation in the microwave region of the electromagnetic spectrum.
- The entire range of electromagnetic radiation constitutes the electromagnetic spectrum.
- Microwave sensors detect electromagnetic waves.
Remote Sensing Fundamentals
- The entire range of electromagnetic radiation constitutes the electromagnetic spectrum.
- Microwave remote sensing detects EM radiation in the microwave region.
- Visible spectrum wavelengths range from .400 to .700 micrometers
Radar Wavelengths
- Radar uses various frequency bands (Ka, Ku, X, C, S, L, P).
- Each band has a specific range of wavelengths and corresponding frequencies.
- Water vapor and oxygen absorption bands influence microwave transmission.
Radar Wavelengths (Detailed)
- A table showing the relationship between frequency bands, wavelengths (in cm), and corresponding frequencies (in GHz) for different radar bands is presented
- The formula f (in Hertz) = C/λ where C is the speed of light and λ is the wavelength is given.
Microwave Remote Sensing
- Active microwave sensors emit their own energy.
- Passive microwave sensors detect naturally emitted energy.
- Passive sensors are typically radiometers or scanners.
- They typically have low spatial resolution.
- Low spatial resolution is a characteristic of passive microwave sensors.
- Resolution and application types are interlinked
- Land, Ocean, and atmospheric applications
- Examples include soil moisture, glacier studies, SST, wind speed, cloud liquid water, and rainfall rate.
Passive Microwave Sensing from Space
- Microwave sensors can penetrate non-precipitating clouds.
- Radiance is linearly related to temperature.
- Sensors have a consistent calibration.
- Global coverage and wide swaths are possible.
- Disadvantages include larger field of view compared to visible or infrared sensors and variable emissivity across land surfaces.
Passive Microwave Applications
- Applications include measuring snow water equivalent, sea/lake ice extent, and atmospheric water vapor.
- Measurement of sea surface temperature, surface wind speed, cloud liquid water, and rainfall rate are also possible.
Brightness Temperature and Emissivity
- Microwave radiometers measure brightness temperature.
- It's related to the kinetic temperature of the surface.
- Rayleigh-Jeans approximation provides a linear relationship with emissivity.
- Emissivity is a dimensionless material property.
- It's a ratio of energy radiated by a material to energy radiated by a black body at the same temperature.
- A table lists emissivity values for water and sand, and highly polished silver.
Active Microwave Remote Sensing
- Active sensors emit their own microwave radiation.
- Categorized into imaging and non-imaging types.
- RADAR is a common imaging technique.
- RADAR measures backscattered signal strength.
- Radar range (R) is calculated from transmission time (t) and speed of light (c).
Viewing Geometry and Spatial Resolution
- Radar systems often use side-looking and oblique geometry.
- Imaging geometry differs from optical systems.
- Range refers to the perpendicular distance, while azimuth is parallel to the flight direction.
- The illumination width (swath) can be affected by the radar beam's width and distance from the sensor.
Synthetic Aperture Radar (SAR)
- SAR increases azimuth resolutions of radar.
- Simulates a larger antenna through signal processing and platform movement is a core function.
- SAR viewing geometry depends on the positioning and movement of the platform and the target position.
Satellite Altimeters
- Satellite altimeters measure sea-level topography and variability of currents
- Measurement accuracy is high.
- Altimeters measure the time it takes for the pulse to travel to the surface and back to the satellite.
Various Parameters Using Microwave
- Sea surface temperature (SST) measured via passive sensing of emitted thermal radiation.
- Examples of sensors used for active microwave include AVHRR, MODIS, VIIRS, SMMR, SSM/I, TRMM-TMI, and AMSR-E.
- SST images help with fisheries management, climate monitoring, forecasts, atmospheric model validation, and identifying coral bleaching.
Radar Backscatter Coefficient, Roughness, and Wavelength Dependence
- Radar backscatter coefficient quantifies how efficiently a surface reflects radar signals.
- It is inversely proportional to the area and surface roughness of a target.
- Backscattering varies with surface roughness and wavelength.
- Rayleigh criterion describes when a surface is considered smooth with respect to wavelengths.
- A smoother surface has smaller height variations.
- The diagram illustrates how radar backscattering is dependent on surface roughness and incidence angle.
- The backscattering coefficient drops as the wavelength lengthens.
Summary of Microwave Applications
- Various phenomena including water vapor, ocean currents, rainfall, and surface temperature can be detected using microwave sensors.
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Description
This quiz covers the fundamentals of microwave remote sensing, including the electromagnetic spectrum and radar wavelengths. Test your understanding of how microwave sensors detect EM radiation and the various frequency bands used in radar. Suitable for students and enthusiasts of remote sensing technology.
